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0801.2461

c

we have introduced quadratic form expansions , and developed techniques which suggest that they may be useful for synthesizing efficient implementations for unitary operations . we described conditions under which implementations may be efficiently found for unitaries specified by quadratic form expansions ; and we showed how quadratic form expansions leads to more efficient algorithms for obtaining reduced patterns for clifford operations in the one way measurement model . in the introduction , we mentioned that quadratic form expansions are similar in form to a sum - over - paths representation of unitary operations , which is a well - developed subject in theoretical physics . this raises the question of whether the techniques developed here are useful e.g. for developing algorithms to simulate physical systems . it is not known whether the solved cases of the measurement pattern interpolation problem correspond to _ natural _ ( in the more literal sense ) unitaries expressed as sums over paths : this question , and how to extend the solved cases of the mpi to include propagators for interesting physical systems , remain open . 000 r. raussendorf and h. briegel . _ a one - way quantum computer_. physical review letters 86 ( 5188 ) , 2001 . r. raussendorf and h. briegel . _ computational model underlying the one - way quantum computer_. quantum information & computation , vol 2 # 6 ( 443 ) 2002 . a. broadbent and e. kashefi . _ parallelizing quantum circuits_. arxiv:0704.1736 , 2007 . r. p. feynmann , a. r. hibbs . _ quantum mechanics and path integrals_. mcgraw - hill , new york , 1965 . l. s. schulman . _ techniques and application of path integration_. wiley - interscience , new york , 1981 . v. danos and e. kashefi . _ determinism in the one - way model_. physical review a 74 ( 052310 ) , 2006 . arxiv : quant - ph/0506062 . d. e. browne and h. j. briegel . _ one - way quantum computation a tutorial introduction_. arxiv : quant - ph/0603226 ( 2006 ) . d. e. browne , e. kashefi , m. mhalla , and s. perdrix . _ generalized flow and determinism in measurement - based quantum computation_. new j. physics vol . 9 ( 250 ) , 2007 . arxiv : quant - ph/0702212 c. m. dawson , h. l. haselgrove , a. p. hines , d. mortimer , m. a. nielsen , and t. j. osborne . _ quantum computing and polynomial equations over _ . quantum information & computation vol 5 # 2 ( 102 ) , 2004 . arxiv : quant - ph/0408129 n. de beaudrap , v. danos , and e. kashefi . _ phase map decompositions for unitaries_. arxiv : quant - ph/0603266 , 2006 . v. danos , e. kashefi , and p. panangaden . _ the measurement calculus . _ j. acm vol . 54 , 8 ( 2007 ) . arxiv : quant - ph/0412135 v. danos , e. kashefi , and p. panangaden . _ parsimonious and robust realizations of unitary maps in the one - way model_. physical review a vol 72 ( 064301 ) , 2005 . arxiv : quant - ph/0411071 m. mhalla and s. perdrix . finding optimal flows efficiently . arxiv:0709.2670 , 2007 . a. kitaev , a. shen , and m. vylalyi . _ classical and quantum computation_. graduate texts in mathematics , vol 47 , american mathematical society , providence ri , 2002 . n. de beaudrap and m. pei . _ an extremal result for geometries in the one - way measurement model_. to appear in quantum information and computation , vol . 8 # 5 ( 430 ) , 2008 . arxiv : quant - ph/0702229 d. gottesman . . phd thesis , caltech , 1997 . arxiv : quant - ph/9705052 . j. dehaene and b. de moor . _ clifford group , stabilizer states , and linear and quadratic operations over _ . physical review a vol 68 ( 042318 ) , 2003 . arxiv : quant - ph/0304125 m. hein , j. eisert , and h. j. briegel . _ multi - party entanglement in graph states . _ physical review a vol 69 ( 62311 ) , 2004 . arxiv : quant - ph/0307130 s. aaronson and d. gottesman . _ improved simulation of stabilizer circuits_. physical review a vol 70 ( 052328 ) , 2004 . arxiv : quant - ph/0406196 n. de beaudrap . finding flows in the one - way measurement model . arxiv : quant - ph/0611284 , 2006 . a. fowler , s. devitt , and l. hollenberg . _ implementation of shor s algorithm on a linear nearest neighbor qubit array_. quantum information & computation vol 4 # 4 ( 237 ) , 2004 . k. n. patel , i. l. markov , and j. p hayes . efficient synthesis of linear reversible circuits . to appear in quantum information & computation vol 8 , 2008 . arxiv : quant - ph/0302002

we introduce techniques to analyze unitary operations in terms of _ quadratic form expansions _ , a form similar to a sum over paths in the computational basis when the phase contributed by each path is described by a quadratic form over . we describe various conditions under which it is possible to efficiently implement a unitary operation , either when provided a quadratic form expansion for as input , or by finding a quadratic form expansion for from other input data .

we introduce techniques to analyze unitary operations in terms of _ quadratic form expansions _ , a form similar to a sum over paths in the computational basis when the phase contributed by each path is described by a quadratic form over . we show how to relate such a form to an entangled resource akin to that of the one - way measurement model of quantum computing . using this , we describe various conditions under which it is possible to efficiently implement a unitary operation , either when provided a quadratic form expansion for as input , or by finding a quadratic form expansion for from other input data .

0805.1305

i

in the context of tropical geometry , it is well known that two tropical curves may share an infinite number of intersection points without sharing a common component . this problem is avoided with the notion of stable intersection , @xcite . given two curves , there is a well defined set of intersection points that varies continuously under perturbations of the curves . this stable intersection has very nice properties . for example , it verifies a tropical version of bernstein - koushnirenko theorem ( cf . an alternative way of defining a finite intersection set is the following : given two tropical curves @xmath0 and @xmath1 , take two algebraic curves @xmath2 and @xmath3 projecting onto the tropical curves . then , the intersection of the two algebraic curves @xmath4 will project into the intersection of the tropical curves , @xmath5 . in general , the set @xmath6 depends on the election of the curves @xmath2 and @xmath3 . we are proving that , if the coefficients of @xmath2 , @xmath3 are generic , then the algebraic intersection will project exactly onto the stable intersection and there is a correspondence among the multiplicities of the intersection points . moreover , given two curves , we compute residually dense sufficient conditions defining these genericity conditions . the method works in any characteristic and it is essential in the generalization of the geometric construction method of @xcite to the non linear case . this also provides a particular case of bernstein - koushnirenko theorem for fields of positive characteristic . in order to prove this relationship , we introduce the notion of tropical resultant , as the tropicalization of the algebraic resultant . the paper is structured as follows . in section [ sec_notions ] , we give a brief description of the algebraic context we will work in . next , in section [ intersec_estable ] we recall the notion of stable intersection for plane curves and provide a brief discussion about its properties . then , it is introduced the notion of tropical resultant for univariate polynomials ( section [ sec_univariate ] ) and plane curves ( section [ sec_bivariate ] ) . in section [ sec_stable_int ] , we relate the stable intersection of tropical curves with the resultant of the curves and the generic preimage under the tropicalization map . we will provide conditions for the lifts ( preimages ) to be compatible with the stable intersection and the correspondence of the multiplicities . finally , in section [ sec_remarks ] we present some comments and remarks about the results .

we introduce the notion of resultant of two planar curves in the tropical geometry framework . it is shown that , for two generic preimages of the curves to an algebraic framework , their intersection projects exactly onto the stable intersection of the curves . _ keywords _ : tropical geometry , resultants , plane curves msc2000 : 14m25 , 14h50 , 52b20

we introduce the notion of resultant of two planar curves in the tropical geometry framework . we prove that the tropicalization of the algebraic resultant can be used to compute the stable intersection of two tropical plane curves . it is shown that , for two generic preimages of the curves to an algebraic framework , their intersection projects exactly onto the stable intersection of the curves . it is also given sufficient conditions for such a generality in terms of the residual coefficients of the algebraic coefficients of defining equations of the curves . _ keywords _ : tropical geometry , resultants , plane curves msc2000 : 14m25 , 14h50 , 52b20

astro-ph0305288

c

in this paper we have considered the axisymmetric force - free magnetosphere of an aligned rotating magnetic dipole , under the additional assumptions of ideal mhd and of the uniformity of the field - line angular velocity [ @xmath289 . this fundamental model problem is of great importance to any attempts to understand the workings of radio - pulsars . more specifically , we have focussed most of our attention on the structure of the magnetic field in the vicinity of the point of intersection of the separatrix ( between the closed- and open - field regions ) and the equator . we call this point the separatrix intersection point . the unique singular nature of this point makes it play an extremely important role in the overall global problem ; in particular , without a thorough understanding of the subtleties of the magnetic field behavior near this point , it is impossible to prescribe the correct global boundary conditions in any sensible way . we start , however , by discussing ( in [ sec - basic ] ) the basic equations governing the global force - free pulsar magnetosphere . we give special attention to the role played by the light cylinder regularity condition in determining the poloidal electric current . after this general discussion , the rest of the paper is devoted entirely to the analysis of the separatrix intersection point . we first consider the separatrix equilibrium condition in the vicinity of this point ( see [ sec - y - point ] ) and find that if it lies at the light cylinder , then all the poloidal current @xmath35 has to return back to the pulsar in the open - field region above the equator , i.e. , there should be no singular current running in a current sheet along the equator and the separatrix . we then perform ( in [ sec - analysis ] ) an asymptotic analysis of the relativistic grad shafranov , or pulsar , equation in the vicinity of such an intersection point located at the light cylinder . we find a unique self - similar solution that can be described by the power law @xmath290 , where @xmath139 is the distance form the intersection point and @xmath291 , and by the equator separatrix angle @xmath292 rad . however , a further analysis of this solution in the region outside the light cylinder shows that a light surface ( a surface where @xmath293 ) appears just outside the light cylinder ; in particular , we find that this light surface originates right at the intersection point and extends outward at a finite angle with respect to the equator . the appearance of a light surface in this case is , of course , not surprising , taking into account the fact that ( in this case of the separatrix intersection point lying at the light cylinder ) the poloidal electric current @xmath125 and hence the toroidal magnetic field have to become zero on the last open field line . we therefore conclude that the only possibility for an ideal - mhd force - free magnetosphere above the putative equatorial current sheet to extend at least some finite distance beyond the light cylinder , is for the separatrix intersection point to be located inside , as supposed to right at , the light cylinder . ( of course we understand that the exact location of this point can only be found as a part of a global solution of the pulsar equation and that it is impossible to determine it from our local analysis ) . these findings give us the motivation to consider the case when the intersection point lies at some finite distance inside the light cylinder . in [ sec - t - point ] we examine the behavior of the function @xmath35 near the last open field line @xmath72 ( above the equatorial current sheet ) for this case ; we find that the derivative @xmath294 has to go to zero as @xmath295 , whereas the current itself can approach a finite value @xmath86 . we then perform an asymptotic analysis of the magnetic field around the intersection point ; it is essentially a somewhat simplified and trivialized analogue of our analysis in [ sec - analysis ] . we find that the separatrix approaches the equator at a right angle , @xmath68 , and that the field in the region of open field lines behaves simply as @xmath296 , while in the closed - field region the magnetic field is simply vertical and finite near the intersection point ( we call this configuration the t - point ) . finally , we would like to make several remarks regarding the numerical simulations by ckf and by ogura & kojima ( 2003 ) : \1 ) the midplane boundary conditions ( @xmath297 , @xmath298 ; @xmath51 , @xmath299 ) adopted by both groups have automatically assumed that the separatrix intersection point lies at the lc , and thus have precluded them from even considering the possibility @xmath64 . it is interesting to note , however , that from the magnetic contour plots presented by ogura & kojima ( 2003 ) it does seem that the actual intersection point lies a little bit inside the lc . \2 ) neither ckf , nor ogura & kojima ( 2003 ) have discussed or even mentioned the separatrix equilibrium condition ; thus it is not clear whether this condition has been satisfied in their simulations . in the light of our present findings and of the fact that both of these groups have found @xmath86 , we suspect that the equilibrium condition has not , in fact , been satisfied in their studies , at least close to the separatrix intersection point . this suspicion is strengthened by the fact that both groups have reported having experienced some difficulties near the separatrix . \3 ) ogura & kojima ( 2003 ) have reported that they had found @xmath300 at some finite distance outside the lc , whereas ckf have claimed that in their solution @xmath301 everywhere . the origin of this discrepancy is not clear . it may be attributed to the difference in numerical resolution , although neither of the two groups have conducted very extensive convergence studies . i am grateful to leonid malyshkin and anatoly spitkovsky for interesting and insightful discussions . this research was supported by the national science foundation under grant no . phy99 - 07949 .

we investigate the axisymmetric magnetosphere of an aligned rotating magnetic dipole surrounded by an ideal force - free plasma . we concentrate on the magnetic field structure around the point of intersection of the separatrix between the open and closed field - line regions and the equatorial plane . we find that in this case the separatrix equilibrium condition implies that all the poloidal current must return to the pulsar in the open - field region , i.e. , that there should be no finite current carried by the separatrix / equator current sheet . we then perform an asymptotic analysis of the pulsar equation near the intersection point and find a unique self - similar solution ; however , a light surface inevitably emerges right outside the light cylinder .

we investigate the axisymmetric magnetosphere of an aligned rotating magnetic dipole surrounded by an ideal force - free plasma . we concentrate on the magnetic field structure around the point of intersection of the separatrix between the open and closed field - line regions and the equatorial plane . we first study the case where this intersection point is located at the light cylinder . we find that in this case the separatrix equilibrium condition implies that all the poloidal current must return to the pulsar in the open - field region , i.e. , that there should be no finite current carried by the separatrix / equator current sheet . we then perform an asymptotic analysis of the pulsar equation near the intersection point and find a unique self - similar solution ; however , a light surface inevitably emerges right outside the light cylinder . we then perform a similar analysis for the situation where the intersection point lies somewhere inside the light cylinder , in which case a finite current flowing along the separatrix and the equator is allowed . we find a very simple behavior in this case , characterized by a 90-degree angle between the separatrix and the equator and by finite vertical field in the closed - field region . finally , we discuss the implications of our results for global numerical studies of pulsar magnetospheres .

1203.5522

i

the present paper is devoted to the phenomena of bose einstein condensation ( bec for short ) on non homogeneous networks obtained by adding density zero perturbations to homogeneous cayley trees . even if the unperturbed model already exhibit bec ( cf . @xcite ) , the arising picture for the perturbed situation deserves attention as we have already explained in @xcite , and we are going to study in details in the sequel . the present paper is then the second part of the previous one @xcite , in which the harmonic analysis aspects of the model were intensively studied . the reader is also referred to @xcite for some very interesting pivotal amenable models . we are going to investigate the physical application to the bec of the very fascinating picture which arises from the previous mathematical investigation . the physical underlying model concerns bardeen cooper boson pairs in networks describing arrays of josephson junctions . the formal hamiltonian is the quartic bose hubbard hamiltonian , given on a generic network @xmath4 by @xmath5 here , @xmath6 denotes the set of the vertices of the network @xmath4 , @xmath7 is the bosonic creator , and @xmath8 the number operator on the site @xmath9 ( cf . @xcite ) . finally , @xmath10 is the adjacency operator whose matrix element @xmath11 in the place @xmath12 is the number of the edges connecting the site @xmath13 with the site @xmath14 ( in particular it is hermitian ) . the reader is referred to the seminal paper @xcite in which the theory of the superconductivity ( called bcs theory in honor of the authors ) has been firstly discussed . it has been argued in @xcite that , in the case when @xmath15 and @xmath16 are negligible with respect to @xmath17 , the hopping term dominates the physics of the system . after neglecting such terms , putting for the resulting effective coupling constant @xmath18 , in principle different from @xmath17 , @xmath19 , and finally passing to the one particle space , the model under consideration becomes the so called pure hopping ones described by the _ pure hopping one particle hamiltonian _ which assumes the form @xmath20 here , @xmath10 is simply the adjacency of the fixed graph @xmath4 , acting on the hilbert space @xmath21 . the constant @xmath22 is added just in order to have @xmath23 and does not affect the analysis at all . the reader is referred to @xcite for the systematic investigation of the mathematical properties arising in non amenable cases considered here consisting of negligible additive perturbations of cayley trees . several interesting amenable models are treated in details in @xcite . the reader is also referred to @xcite for some promising experiments for the pure hopping model on the comb and star graphs ( see fig . [ figd ] ) pointing out an enhanced current at low temperature which might be explained by condensation phenomena . one of the first attempts to investigate the bec on non homogeneous amenable graphs , such as the comb graphs , was made in @xcite . in that paper , it was pointed out the appearance of a _ hidden spectrum _ in the low energy part of the spectrum , which is responsible of the finiteness of the critical density . in addition , the behavior of the wave function of the ground state , describing the spatial density of the condensate , was also computed . some spectral properties of the comb and the star graph were also investigated in @xcite in connection with the various notions of independence in quantum probability . in that paper , it was noted the possible connection between such spectral properties and the bec . the systematic investigation of the bec for the pure hopping model on a wide class of amenable networks obtained by negligible perturbations of periodic graphs , has been started in @xcite . the emerging results are quite surprising . first of all , the appearance of the hidden spectrum was proven for most of the graphs under consideration . this is due to the combination of two opposite phenomena arising from the perturbation . if the perturbation is sufficiently large ( surprisingly , in some examples , it is enough that the perturbation is indeed finite ) , the norm @xmath24 of the adjacency of the perturbed graph becomes larger than the analogous one @xmath22 of the unperturbed adjacency . on the other hand , as the perturbation is sufficiently small ( i.e. zero density ) , the part of the spectrum @xmath25 in the segment @xmath26 $ ] does not contribute to the density of the states . this allows to compute the critical density @xmath27 at the inverse temperature @xmath28 for the perturbed model by using the integrated density of the states @xmath29 of the unperturbed one , @xmath30 the resulting effect of the perturbed model exhibiting the hidden spectrum ( i.e. when @xmath31 ) is that the critical density is always finite . the bridge between the mathematics and physics can be easily explained as follows . consider the bose gibbs occupation number ( at the inverse temperature @xmath32 and chemical potential @xmath33 ) at low energies for the hamiltonian . after using taylor expansion , one heuristically gets @xmath34^{-1}=[\b((\|a\|-\m)i - a)]^{-1 } \equiv \frac1{\b}r_a(\|a\|-\m)\,.\ ] ] then the study of the bec is reduced to the investigation of the spectral properties of the resolvent @xmath35 , for @xmath36 , the latter being a very familiar object for mathematicians . due to the particular form , as the bec phenomena are connected with the spectral properties for small energies of the hamiltonian , we can reduce the matter to the investigation of the spectral properties of the adjacency operator @xmath10 of the network close to @xmath22 . another relevant fact connected with the introduction of the perturbation , and thus with the lack of homogeneity , is the possible change of the transience / recurrence character ( cf . @xcite , section 6 ) of the adjacency operator . it has to do with the possibility to construct locally normal states exhibiting bec . as explained in @xcite , the last relevant fact is the investigation of the shape of wave function of the ground state of the model , describing the spatial distribution of the condensate on the network in the ground state of the hamiltonian . from the mathematical viewpoint , this is nothing else the perron frobenius generalized eigenvector of the adjacency ( cf . it appears then clear that the physical and the mathematical aspects of the topological model based on the pure hopping hamiltonian are strongly related . summarizing , the new and very surprising phenomena are the following . first the finiteness of the critical density is connected with the appearance of the _ hidden spectrum _ above the zero of the energy . it can be computed in a quite simple way for many amenable and non amenable models by using the _ secular equation _ , see section 6 of @xcite and section 3 of @xcite . this leads to the fact that the bec can appear also in low dimensional cases @xmath37 . in addition , not for all the models with finite critical density , it is possible to exhibit locally normal states ( those for which the local particle density is finite in the infinite volume limit ) describing bec . due to non homogeneity , particles condensate also in the configuration space , that is the system undergoes a `` dimensional transition '' . this phenomenon is connected with the _ transience / recurrence _ character of the adjacency operator of the network ( the last describing the hamiltonian of the system ) . another new aspect is the difference between the geometrical dimension of the network and the growing of the wave function of the ground state . the last is called _ perron frobenius dimension _ @xmath38 for volume growing networks and is computed through the behavior of @xmath39norms of the finite volume perron frobenius eigenvectors , all normalized to @xmath40 at a common root . if the geometrical dimension @xmath41 is greater than @xmath38 , then it is impossible to exhibit locally normal states describing the bec , whose mean density of the particles is greater than the critical one . surprisingly , there are non homogeneous networks for which @xmath42 and @xmath43 ( i.e. the comb graph @xmath44 , see fig . [ figg ] ) . in addition , there are also simple non homogeneous graphs exhibiting infinite critical density , but for which it is yet possible to exhibit locally normal states describing bec . such a very intriguing situation is summarized as follows . is the comb shaped graph whose base point is @xmath10 , @xmath2 is the critical density , r / t denotes the recurrence / transience character of the adjacency , bec ( @xmath45bec ) denotes the existence of locally normal states exhibiting bec ( exhibiting bec at any mean density @xmath46 ) . ] [ cols="<,<,^,^,^,^,^,^",options="header " , ] a similar situation also happens for some non amenable networks . the networks under consideration in the present paper are density zero additive perturbations of exponentially growing graphs made of homogeneous cayley trees , see fig . the models treated in the present paper are the perturbations @xmath47 , @xmath48 , and @xmath49 , of the homogeneous cayley tree @xmath50 along a subtree isomorphic to @xmath51 , and @xmath52 respectively , see below , see also @xcite for the precise definition of such models and for further details . quite surprisingly , the emerging mathematical situation described in @xcite for such non amenable examples , is similar to that for the amenable graphs treated in @xcite . namely , we still find hidden spectrum , and the transience / recurrence character is determined by the transience / recurrence character of the negligible subgraph supporting the perturbation . finally , the infinite volume perron frobenius eigenvector is exponentially decreasing far from the base point supporting the perturbation . namely , concerning the wave function of the ground state , we have precisely the same situation arising for the amenable situations treated in @xcite ( see fig . [ figd ] ) . the first part of the present paper is devoted to describe general properties of ( bounded ) hamiltonians on networks equipped with an exhaustion such that the density of the eigenvalues of the underlying hamiltonian converges in the infinite volume limit to a cumulative function called _ integrated density of the states_. it includes as particular cases those arising by negligible perturbations of cayley trees as shown in @xcite . then we describe the general statistical properties of such models . in particular , a careful definition of the mean density and the possible amount of the bec condensate should be done , because of the non negligible effects of the boundary terms due to the possible lack of amenability . we pass to describe the existence of the dynamics associated to the pure hopping hamiltonian for the perturbed cayley trees . this is a delicate issue which is done in section [ dynkmss ] for all the cases under consideration . after that , by using the results in @xcite , in the transient case we write down the formula ( cf . ) for the natural class of states describing bec ( i.e. presenting a non negligible amount of condensate in the ground state wave function ) . such states are kms ( i.e. equilibrium ) states for the dynamics previously investigated . as for the previous amenable models treated in @xcite , such states are infinite volume kms states whose mean density coincides with the critical one . this simply means that the condensate is allocated on a subgraph whose volume growth is negligible with respect to that of the unperturbed one . we end the paper by investigating the infinite volume behavior of finite volume gibbs states . due to the lack of amenability , such an investigation presents some very delicate technical difficulties arising by the unavoidable boundary effects . modulo such difficulties , the emerging situation seems to be in accordance with that described in @xcite , and summarized as follows . first , relatively to the general recurrent situation , it is indeed impossible to construct locally normal states exhibiting bec at all , even if the critical density is finite . in addition , in the all transient cases under consideration , it seems to be impossible to exhibit locally normal states describing bec at the mean density @xmath53 , @xmath54 . finally , in the condensation regime where for the mean density @xmath1 of all such states @xmath55 , a careful choice of the sequence of the finite volume chemical potentials @xmath56 should be done . by considering the geometry of the graph @xmath4 and the @xmath39behavior of the ground state wave function @xmath57 , such a choice corresponds to the local density of the condensate @xmath58 in the infinite volume limit @xmath59 , see proposition [ 3a3c ] . this is nothing but the naive explanation of the fact that @xmath55 for the locally normal states describing the condensation regime in all the situations under consideration .

we investigate the bose einstein condensation on non homogeneous non amenable networks for the model describing arrays of josephson junctions . the graphs under investigation are obtained by adding density zero perturbations to the homogeneous cayley trees . the present paper is then the application to the bose einstein condensation phenomena , of the harmonic analysis aspects , previously investigated in a separate work , for such non amenable graphs . concerning the appearance of the bose einstein condensation , the results are surprisingly in accordance with the previous ones , despite the lack of amenability . the appearance of the hidden spectrum for low energies always implies that the critical density is finite for all the models under consideration . first we show that , even when the critical density is finite , if the adjacency operator of the graph is recurrent , it is impossible to exhibit temperature states which are locally normal ( i.e. states for which the local particle density is finite ) describing the condensation at all . a similar situation seems to occur in the transient cases for which it is impossible to exhibit locally normal states describing the bose einstein condensation at mean particle density strictly greater than the critical density . the condensate is essentially allocated on the base point supporting the perturbation . this leads to . the construction of such a dynamics , which is a delicate issue , is also done .

we investigate the bose einstein condensation on non homogeneous non amenable networks for the model describing arrays of josephson junctions . the graphs under investigation are obtained by adding density zero perturbations to the homogeneous cayley trees . the resulting topological model , whose hamiltonian is the pure hopping one given by the opposite of the adjacency operator , has also a mathematical interest in itself . the present paper is then the application to the bose einstein condensation phenomena , of the harmonic analysis aspects , previously investigated in a separate work , for such non amenable graphs . concerning the appearance of the bose einstein condensation , the results are surprisingly in accordance with the previous ones , despite the lack of amenability . the appearance of the hidden spectrum for low energies always implies that the critical density is finite for all the models under consideration . first we show that , even when the critical density is finite , if the adjacency operator of the graph is recurrent , it is impossible to exhibit temperature states which are locally normal ( i.e. states for which the local particle density is finite ) describing the condensation at all . a similar situation seems to occur in the transient cases for which it is impossible to exhibit locally normal states describing the bose einstein condensation at mean particle density strictly greater than the critical density . indeed , it is shown that the transient cases admit locally normal states exhibiting bose einstein condensation phenomena . in order to construct such locally normal temperature states by infinite volume limits of finite volume gibbs states , a careful choice of the the sequence of the chemical potentials should be done . for all such states , the condensate is essentially allocated on the base point supporting the perturbation . this leads to . we prove that all such temperature states are kubo martin schwinger states for a natural dynamics . the construction of such a dynamics , which is a delicate issue , is also done .

1307.7776

r

we estimate the critical migration timescale in a manner similar to that of @xcite . orbital integrations of two planets are performed with various parameters to determine whether the planets are captured into 2:1 mean motion resonances . figure [ fig : t_a ] shows the evolution of the semimajor axes and eccentricities of the two planets with a migration timescale @xmath9 of @xmath49 in the fiducial model . when a 2:1 commensurability is formed at @xmath50 , the eccentricities are excited . we also confirm that the two resonant angles and @xmath51 , where @xmath52 and @xmath53 are mean orbital longitudes and longitudes of the pericenter , respectively . ] librate about fixed values . we made 10 runs for each migration timescale with different initial orbital phase angles and derived the capture probability @xmath54 of 2:1 resonances . when the period ratio lies within an error of 1% , we call it a resonant capture . note that the long term stability of the resonant configuration is not considered . figure [ fig : ta_p_fiducial](a ) shows the capture probability for the fiducial model as a function of the migration time . the probability @xmath54 is assumed to have the form @xmath55^{-1},\end{aligned}\ ] ] where @xmath1 is defined as the migration time for which @xmath56 and @xmath57 is a constant . using a least squares fit to the data ( solid line ) , we specify @xmath1 and @xmath57 . the capture probability increases sharply at @xmath58 , which means that the critical migration time @xmath1 can be estimated without introducing large errors @xmath59 . figure [ fig : ta_p_fiducial](b ) presents the results for an initial eccentricity of @xmath60 . in this case , the eccentricity is 0.01 at the resonant encounter because the inner body does not undergo eccentricity damping . in contrast to low @xmath7 , high eccentricities reduce @xmath54 at @xmath61 @xmath62 , and @xmath54 gradually increases with @xmath9 @xmath63 . this broadening of the capture probability curve at higher eccentricity is also seen in previous studies ( e.g. , @xcite ; @xcite ) . we find that the critical migration timescale can be sharply defined except when the eccentricity is not small @xmath64 at the resonant encounter . in the following subsections , the value of @xmath57 is explicitly described only when the transition is not sharp enough . the eccentricity dependence of @xmath54 is summarized in section [ sec : eini ] . we performed @xmath65 runs for each set of parameters ( @xmath66 runs in total ) . we first examine the dependence of the critical migration timescale on the mass of the larger body @xmath3 . figure [ fig : m1_ta ] illustrates how @xmath1 varies with @xmath3 . open squares ( connected by a solid line ) represent the fiducial case , where @xmath67 , and @xmath68 with different values of @xmath3 . filled squares , open circles , filled circles , and open triangles show the results for @xmath69 and @xmath70 respectively , but the other parameters are the same as for the fiducial case . note that the open squares and open circles overlap at every @xmath3 . the dependence on @xmath71 is examined between @xmath72 and @xmath73 . in order to keep computational cost reasonable , we also put an upper limit of @xmath74 . for @xmath75 , the eccentricity of the inner body is @xmath76 at the resonant encounter and the capture probability curve is broadened ( @xmath77@xmath78 ) . this survey reveals two features . first , all of the @xmath1 values except that for @xmath79 are within about a factor of two of each other . this suggests that @xmath1 depends weakly on @xmath80 and @xmath7 , which can be seen in the following subsections in more detail . second , all the cases exhibit a similar power law dependence of @xmath1 on @xmath3 . the gradients are calculated for each case by least squares fits , and we obtain a typical power index approximately equal to @xmath0 . a physical interpretation for this dependence is discussed in section [ sec : discussion ] . next , we explore the effect of varying @xmath81 note that the dependence can be seen more clearly when @xmath31 is used instead of @xmath4 . figure [ fig : m2_ta ] shows @xmath1 as a function of @xmath81 open squares represent the fiducial case . filled squares , open circles , filled circles , and open triangles show the results for @xmath82 , and @xmath70 respectively . same as the previous subsection , the capture probability curve is not sharp for @xmath75 ( @xmath83@xmath84 ) . we find that if @xmath85 @xmath1 is independent of @xmath31 ; therefore , the restricted three body approximation is valid for this condition . the difference between @xmath1 for @xmath86 and the value for small @xmath31 is found to be a factor of about 10 . thus , although the restricted three body approach can not provide an accurate prediction of @xmath1 for bodies with comparable masses , it would be possible to roughly derive @xmath1 to an accuracy of a factor of 10 . see also discussions in sections [ sec : internal_resonance ] and [ sec : compare ] for the reason for the difference . note that we consider only the migration of the outer planet . because migration speed depends on planetary mass , the inner planet s migration is not negligible , especially for @xmath87 . however , if we apply the differential migration speed instead of the migration speed of the outer planet , the critical migration timescales we obtain are valid even considering the migration of both planets . figure [ fig : te1_ta ] shows the results for various eccentricity damping timescales for the inner ( larger ) planet , @xmath20 . again , the open squares represent the fiducial case . filled squares , open circles , filled circles , and open triangles show the results for @xmath88 , and @xmath70 respectively . the rightmost points on the horizontal axis are the cases without eccentricity damping . for @xmath75 and @xmath24 , the transition from a capture probability of zero to one is not very sharp ( @xmath77 ) . there is no systematic change in @xmath1 with @xmath89 even when @xmath20 is varied by more than four orders of magnitude , the differences in @xmath1 lie within a factor of two or three . figure [ fig : te2_ta ] shows the results for various eccentricity damping timescales for the outer ( smaller ) planet , @xmath21 . open squares represent the fiducial case . filled squares , open circles , filled circles , and open triangles are the results for @xmath90 , and @xmath70 respectively . for @xmath75 , the transition in the capture protability is not sharp ( @xmath77@xmath91 ) . we also do not see any clear trends in @xmath92 although the case with @xmath93 ( open triangles ) shows a slight variation , it still remains within a factor of a few . finally , figure [ fig : e_ta ] shows the results for various initial eccentricities @xmath7 . open squares represent the fiducial case . filled squares , open circles , filled circles , and open triangles are the results for @xmath90 , and @xmath94 respectively . when the eccentricity is not small @xmath64 at the resonant encounter , in other words , when @xmath95 and @xmath96 , the capture probability curve is not sharp the same as before . again , no clear trends in @xmath1 with @xmath7 are recognized . note that , for @xmath97 and @xmath79 ( open circles ) and for @xmath98 ( open triangles ) , @xmath1 can not be determined to have particular values . because the eccentricity of the smaller body @xmath4 at a resonant encounter is relatively large , adequate resonant capture does not occur even for long @xmath9 ; the capture probability does not exceed about 0.3 . except for large @xmath7 , the dependence is reasonably weak . several of these features are in agreement with previous studies , which will be discussed in section [ sec : compare ] . the critical migration timescales derived in the previous subsections are summarized as follows : @xmath99 where the dependence on the stellar mass @xmath44 is included . as shown in the results , @xmath1 can differ by a factor of two or three . although we assume that the inner body is more massive than the outer body @xmath100 , the results are almost the same when the outer one is more massive , which will be seen in section [ sec : internal_resonance ] . the formula is valid if the eccentricities of the smaller planets at a resonant encounter are much smaller than 0.1 . the capture condition for 2:1 mean motion resonances was examined above . we performed additional simulations to evaluate the critical migration timescale for closely spaced first order resonances ( e.g. , 3:2 and 4:3 ) because several exoplanet systems have such commensurabilities . figure [ fig : p_ta ] shows the critical migration timescales for @xmath2 resonances ( @xmath101 ) obtained by numerical simulations . here , we define @xmath102a_1,\ ] ] which roughly corresponds to the orbital separation from the inner planet to the outer planet in the mean motion resonance . open squares represent the results for @xmath103 , whereas filled squares represent those for equal mass bodies ( @xmath86 ) . in each case , the other parameters are set to the fiducial values @xmath104 . we see that the critical migration time decreases with decreasing separation . the critical migration timescale for equal mass bodies ( @xmath105 ) is always shorter than that with bodies that have a high mass ratio ( @xmath106 ) . the difference in @xmath1 is larger at 2:1 resonances than at closely spaced resonances . this is presumably because the strength of the 2:1 external resonance , where `` external '' means that the inner body is the dominant body , is significantly weakened by indirect terms in the disturbing function , which will also be discussed in section [ sec : internal_resonance ] . cccccc mass ratio & 2:1 & 3:2 & 4:3 & 5:4 & 6:5 + @xmath107 & @xmath108 & @xmath109 & @xmath110 & @xmath111 & @xmath111 + @xmath112 & @xmath113 & @xmath114 & @xmath109 & @xmath110 & @xmath110 [ tbl : fitting ] the combined results from the above surveys are plotted in figure [ fig : dis2_m1_ta ] . the solid lines indicate the critical migration timescale for capture into the 2:1 resonance as a function of @xmath3 , which is summarized in equation ( [ eq : ta_crit ] ) . squares , triangles , and inverted triangles are the numerical results for the 3:2 , 4:3 , and 5:4 resonances , respectively . from the results , the critical migration timescale is described as @xmath115 where @xmath116 depends on @xmath117 and the resonant commensurability . we derive the @xmath116 values from the fitting of the results and summarize @xmath116 in table [ tbl : fitting ] . note that although @xmath116 should depend on commensurability , the values are the same between the 5:4 and 6:5 resonances , which suggests that the difference is within the minimum interval of @xmath9 that we set for our investigation . the dashed lines in figure [ fig : dis2_m1_ta ] represent fitting results for equal mass cases @xmath118 . although the approximate fits for closer resonances are considered to be correct within a factor of a few , they should be treated with some caution . we observe that when @xmath119 and @xmath120 , the bodies undergo close encounters before being captured into resonances ; therefore , the bodies do not settle into stable resonant orbits , as indicated by the open symbols in figure [ fig : dis2_m1_ta ] . according to the analysis of the hill stability by @xcite , dynamical stability is almost guaranteed if @xmath121 , where @xmath122 is the mutual hill radius . note that if the orbital separation is within a few tens of percent beyond the critical hill separation , hill stable planetary systems may manifest lagrange instability when the outer planet escapes to infinity ( @xcite ; @xcite ) . there is no analytical criteria that describe lagrange stability , and additional numerical simulation is required to determine whether the system is lagrange stable or not . however , @xcite found that the hill stable condition is a good predictor of lagrange stability . the hill stable condition is rewritten as @xmath123 ^ 3 m_*. \label{eq : critical_mass}\ ] ] the critical masses for equal mass bodies assuming @xmath47 are plotted with crosses connected with by a solid line in figure [ fig : dis2_m1_ta ] . if the mass of the body is larger than the critical mass , the system becomes hill unstable , which is consistent with our results that exhibit close encounters ( open symbols ) . note that even if @xmath124 , the orbit in a resonance can become stable for specific orbital arguments ( some examples are provided in section [ sec : constraints ] ) . this criterion for the instability is a rough estimate , and long term orbital integration can reveal the instability time of planets in closely spaced mean motion resonances . so far , we have carried out simulations in the cases where the inner body is more massive or equal to the outer body . in order to evaluate the difference in @xmath1 between the internal and external resonances , additional simulations for outer massive body are performed . assuming @xmath125 , @xmath126 , @xmath127 , @xmath128 , and @xmath26 , the critical migration timescales are determined for 2:1 , 3:2 , 4:3 , 5:4 , and 6:5 resonances , which are plotted in figure [ fig : p_ta ] with crosses . we find that no significant difference between the internal and external resonances ; in fact , it lies within a factor of two . therefore , as stated in the last sentence of section [ sec : model ] , if the outer body is larger than the inner body , we apply the mass of the larger body to @xmath3 ; equation ( [ eq : ta_gen ] ) is then valid . although the difference is not significant , we see a decrease in @xmath1 at the 2:1 internal resonance , which means that the 2:1 internal resonance is stronger than the 2:1 external resonance . this tendency can be understood in terms of contributions of each term in the disturbing function . for the 2:1 external resonance , the contribution of the direct term is diminished by the indirect term , leading to weakening the strength of the resonance ( @xcite ; @xcite ) . one indicator of the strength of the resonance is @xmath129 in the work of @xcite ( see table 1 in their work for each value ) , where the strength of resonance decreases with increasing @xmath129 . we see that @xmath129 for the 2:1 external resonance is large . the fact that the 2:1 internal resonance is stronger than the 2:1 external resonance would also partially explain the decrease in @xmath130 for equal mass bodies in figures [ fig : m2_ta ] and [ fig : p_ta ] although this can not account for the entire change . we also see in figure [ fig : p_ta ] that internal resonances are slightly weaker than external resonances for closely spaced resonances ( e.g. , 3:2 ) , which is consistent with figure 11 in the work of @xcite .

mass bodies is shorter than that in the restricted problem ; for instance , for the 2:1 resonance between two equal mass bodies , the critical timescale decreases by a factor of 10 . in addition , using the obtained formula , the origin of observed systems that include first

we investigate the condition for capture into first order mean motion resonances using numerical simulations with a wide range of various parameters . in particular , we focus on deriving the critical migration timescale for capture into the 2:1 resonance ; additional numerical experiments for closely spaced resonances ( e.g. , 3:2 ) are also performed . we find that the critical migration timescale is determined by the planet to stellar mass ratio , and its dependence exhibits power law behavior with index . this dependence is also supported by simple analytic arguments . we also find that the critical migration timescale for systems with equal mass bodies is shorter than that in the restricted problem ; for instance , for the 2:1 resonance between two equal mass bodies , the critical timescale decreases by a factor of 10 . in addition , using the obtained formula , the origin of observed systems that include first order commensurabilities is constrained . assuming that pairs of planets originally form well separated from each other and then undergo convergent migration and are captured in resonances , it is possible that a number of exoplanets experienced rapid orbital migration . for systems in closely spaced resonances , the differential migration timescale between the resonant pair can be constrained well ; it is further suggested that several exoplanets underwent migration that can equal or even exceed the type i migration rate predicted by the linear theory . this implies that some of them may have formed _ in situ_. future observations and the use of our model will allow us to statistically determine the typical migration speed in a protoplanetary disk .

1307.7776

c

we investigated capture into first order mean motion resonances in a system of two bodies undergoing damping of the eccentricity and semimajor axis using _ n_body integrations . in some of our calculations , we considered the case in which the mass of one body is negligible . in addition , we also studied systems with equal masses . in fact , orbital calculations were performed with a wide range of parameters ; we found that the critical migration timescale can be described using the mass ratio between the larger body and the central object , and depends weakly on the @xmath19damping timescale and initial eccentricity . the empirical formula is given by equation ( [ eq : ta_crit ] ) , where the critical migration timescale for equal mass bodies is about an order of magnitude shorter than that for systems with a massless particle . we also confirmed the power law dependence of the mass with index @xmath0 . this dependence is also supported by analytical arguments that compare the resonant libration timescale and the migration timescale . additional simulations of closely spaced resonances were run , and empirical fits to the results were derived . all the fitting formulae from our calculations are shown in figure [ fig : dis2_m1_ta ] and table [ tbl : fitting ] . the empirical formula we derived can constrain the relative migration speed in systems of two bodies undergoing convergent migration toward capture into mean motion resonances . this means that our model can be useful for understanding the origins of exoplanet systems in resonances . for systems in closely spaced mean motion resonances ( e.g. , kepler-11 , kepler-60 ) , the migration timescale can be well constrained . it is also possible that the planets formed _ in situ_. the systems in which the orbital separation is smaller than @xmath226 ( e.g. , hr 8799 , gliese 876 ) are believed to become stable owing to resonant effects . lower limits to the relative migration timescale were placed on several systems in 2:1 resonances . the origin of the hd 200964 system , which is in 4:3 resonance , remains unclear . our model also provides constraints on the migration timescale of systems other than exoplanets ( e.g. , the grand tack model of the solar system ) . furthermore , when the number of discovered exoplanets in resonances increases sufficiently in the future , the typical type i and ii migration timescales can be obtained using our results ; future observations will allow us to tackle this issue . note that if the eccentricity at a resonant encounter is large , the capture into resonance becomes probabilistic . in this case , our model can provide only a necessary condition . in this work , we considered first order mean motion resonances , which are certainly important for planets both inside and outside the solar system . in addition , higher order mean motion resonances ( e.g. , 3:1 and 5:2 ) can also be important for specific systems ( e.g. , @xcite ; @xcite ) ; therefore , it would be worth examining the conditions for capture into these resonances in future work . we thank to an anonymous referee for detailed helpful comments . we also thank s. inutsuka for helpful discussions . the numerical computations were conducted in part on the general purpose pc farm at the center for computational astrophysics , cfca , of national astronomical observatory of japan . this work was supported by a grant in aid for jsps fellows ( 23004841 ) . hk gratefully acknowledges the support of a grant in aid from mext ( 23103005 ) . barnes , r. , & greenberg , r. 2005 , , 647 , l163 baruteau , c. , & papaloizou , j. c. b. 2013 , , submitted cochran , w. d. et al . 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gaca , e. 2012 , orig . of life and evol . of the biosph . , 42 , 113 origins of life and evolution of the biosphere , 42 , 113 tanaka , h. , takeuchi , t. , & ward , w. r. 2002 , , 565 , 1257 terquem , c. , & papaloizou , j. c. b. 2007 , , 654 , 1110 veras , d. , & mustill , a. j. 2013 , , in press . walsh , k. j. , morbidelli , a. , raymond , s. n. , obrien , d. p. , mandell , a. m. 2011 , , 475 , 206 weidenschilling , s. j. , & davis , d. r. 1985 , icarus , 62 , 16 wisdom , j. 1980 , , 85 , 8 wittenmyer , r. a. , horner , j. , & tinney , c. g. 2012 , , 761 , 165 wyatt , m. c. 2003 , 598 , 1321 zhou , j .- l . , & lin , d. n. c , 2007 , , 666 , 447 lllllll star & @xmath227 & planet & @xmath228 & @xmath10 ( au ) & mmr [ pair ] & period ratio + gliese 876 & 0.334 & d & 6.68 & 0.0208 & & + & & c & 227 & 0.130 & 2:1 [ b ] & 2.03 + & & b & 723 & 0.208 & 2:1 [ e ] & 2.03 + & & e & 14.6 & 0.334 & & + hd 37124 & 0.83 & b & 215 & 0.534 & & + & & c & 207 & 1.71 & 2:1 [ d ] & 2.10 + & & d & 221 & 2.81 & & + hd 73526 & 1.08 & b & 922 & 0.66 & 2:1 [ c ] & 2.00 + & & c & 795 & 1.05 & & + hd 82943 & 1.18 & c & 639 & 0.746 & 2:1 [ b ] & 2.01 + & & b & 556 & 1.19 & & + hd 128311 & 0.84 & b & 693 & 1.10 & 2:1 [ c ] & 2.05 + & & c & 1020 & 1.76 & & + hr 8799 & 1.56 & e & 2861 & 15 & & + & & d & 3179 & 27 & 2:1 [ c ] & 2.00 + & & c & 3179 & 43 & 2:1 [ b ] & 1.99 + & & b & 2225 & 68 & & + kepler-9 & 1 & d & 6.99 & 0.0273 & & + & & b & 80.1 & 0.14 & 2:1 [ c ] & 2.02 + & & c & 54.4 & 0.225 & & + kepler-18 & 0.972 & b & 6.90 & 0.0447 & & + & & c & 17.2 & 0.0752 & 2:1 [ d ] & 1.94 + & & d & 16.5 & 0.117 & & + kepler-48 & 0.89 & b & 4.79 & & 2:1 [ c ] & 2.02 + & & c & 10.6 & & & + kepler-51 & 1.00 & b & 55.9 & & 2:1 [ c ] & 1.89 + & & c & 36.2 & & & + kepler-52 & 0.54 & b & 4.61 & & 2:1 [ c ] & 2.08 + & & c & 3.51 & & & + kepler-53 & 0.98 & b & 8.90 & & 2:1 [ c ] & 2.07 + & & c & 10.8 & & & + kepler-56 & 1.37 & b & 16.0 & & 2:1 [ c ] & 2.04 + & & c & 69.7 & & & + kepler-57 & 0.83 & b & 5.03 & & 2:1 [ c ] & 2.03 + & & c & 2.47 & & & + mu ara & 1.08 & c & 10.6 & 0.0909 & & + & & d & 166 & 0.921 & 2:1 [ b ] & 2.07 + & & b & 533 & 1.5 & & + & & e & 577 & 5.235 & & + 24 sex & 1.54 & b & 633 & 1.33 & 2:1 [ c ] & 1.95 + & & c & 273 & 2.08 & & + hd 45364 & 0.82 & b & 59.5 & 0.681 & 3:2 [ c ] & 1.51 + & & c & 209 & 0.897 & & + kepler-49 & 0.55 & b & 7.86 & & 3:2 [ c ] & 1.51 + & & c & 6.88 & & & + kepler-54 & 0.51 & b & 4.61 & & 3:2 [ c ] & 1.51 + & & c & 1.53 & & & + kepler-55 & 0.62 & b & 6.23 & & 3:2 [ c ] & 1.51 + & & c & 5.12 & & & + kepler-58 & 0.95 & b & 8.22 & & 3:2 [ c ] & 1.52 + & & c & 8.71 & & & + kepler-59 & 1.04 & b & 1.22 & & 3:2 [ c ] & 1.51 + & & c & 4.08 & & & + hd 200964 & 1.44 & b & 588 & 1.60 & 4:3 [ c ] & 1.34 + & & c & 286 & 1.95 & & + kepler-60 & 1.11 & b & 5.46 & & 5:4 [ c ] & 1.25 + & & c & 6.44 & & 4:3 [ d ] & 1.33 + & & d & 6.88 & & & + kepler-11 & 0.961 & b & 4.30 & 0.091 & 5:4 [ c ] & 1.26 + & & c & 13.5 & 0.106 & & + & & d & 6.10 & 0.159 & & + & & e & 8.40 & 0.194 & & + & & f & 2.30 & 0.25 & & + & & g & 302 & 0.462 & & + kepler-50 & 1.24 & b & 5.07 & 0.077 & 6:5 [ c ] & 1.20 + & & c & 8.28 & 0.087 & & [ tbl : exoplanets ]

we investigate the condition for capture into first order mean motion resonances using numerical simulations with a wide range of various parameters . we find that the critical migration timescale is determined by the planet to stellar mass ratio , and its dependence exhibits power law behavior with index . this dependence is also supported by simple analytic arguments . this implies that some of them may have formed _ in situ_. future observations and the use of our model will allow us to statistically determine the typical migration speed in a protoplanetary disk .

we investigate the condition for capture into first order mean motion resonances using numerical simulations with a wide range of various parameters . in particular , we focus on deriving the critical migration timescale for capture into the 2:1 resonance ; additional numerical experiments for closely spaced resonances ( e.g. , 3:2 ) are also performed . we find that the critical migration timescale is determined by the planet to stellar mass ratio , and its dependence exhibits power law behavior with index . this dependence is also supported by simple analytic arguments . we also find that the critical migration timescale for systems with equal mass bodies is shorter than that in the restricted problem ; for instance , for the 2:1 resonance between two equal mass bodies , the critical timescale decreases by a factor of 10 . in addition , using the obtained formula , the origin of observed systems that include first order commensurabilities is constrained . assuming that pairs of planets originally form well separated from each other and then undergo convergent migration and are captured in resonances , it is possible that a number of exoplanets experienced rapid orbital migration . for systems in closely spaced resonances , the differential migration timescale between the resonant pair can be constrained well ; it is further suggested that several exoplanets underwent migration that can equal or even exceed the type i migration rate predicted by the linear theory . this implies that some of them may have formed _ in situ_. future observations and the use of our model will allow us to statistically determine the typical migration speed in a protoplanetary disk .

1307.4119

i

searches for supersymmetry ( susy ) performed by the large hadron collider ( lhc ) experiments on the center - of - mass energy @xmath5 tev run data have started to set stringent constraints to the strongly - interacting susy particles . they translate to limits on the susy masses up to @xmath6 tev for gluinos and squarks of the first family @xcite and @xmath7 gev for third generation squarks @xcite . comparatively weaker constraints were obtained for the states that can be only produced through electroweak ( ew ) interactions , such as sleptons , ew gauginos and higgsinos . the resulting bounds are up to @xmath8 gev for selectrons and smuons @xcite and up to @xmath9 gev for charginos @xcite . they often depend on the assumption of available on - shell decays . nevertheless , it is remarkable that the lhc experiments have started especially with the 2012 run data at @xmath10 tev to go considerably beyond lep in testing the ew sector of the theory . such direct searches for ew production of susy particles are of major importance , as the ew - interacting particles can be in principle much lighter than the strongly - interacting ones . in this paper , we want to discuss how the 8 tev run data constrain the parameter space that is compatible with a light neutralino as candidate for cold dark matter ( dm ) . in other words , we aim at answering the following question : how light can the lightest neutralino still be after the 8 tev run of the lhc ? the framework we adopt for our study can be defined as follows : * only the field content of the mssm is considered ; * dm is a thermal relic and a standard history of the universe is assumed ; * the abundance of the lightest mssm neutralino , whose stability is guaranteed by r - parity conservation , is required to not exceed the observed dm relic abundance . we are not going to make any assumption on the origin and the relations among the susy - breaking parameters : in particular we drop the hypothesis of gaugino mass unification that would imply the lower bound for the lightest neutralino mass reported by the pdg @xcite : @xmath11 . instead , we treat all susy soft - masses as free low - energy parameters . as we discuss in the next section , relic density constraints from cosmic microwave background ( cmb ) observations identify the parameter space compatible with light neutralino dark matter and thus the features of the susy spectrum and the lhc phenomenology . in particular , we are going to argue that , under the assumptions listed above , neutralino dm with @xmath12 is only possible in a specific region of the supersymmetric parameter space , featuring relatively light staus and higgsinos . hence , searches based on multi - tau plus missing energy events are particularly promising in order to test such a scenario , as we are going to discuss in detail . a similar study has been presented last year in ref . @xcite . here , we want to generalize the approach of ref . @xcite , by considering a simplified model defined only by the subset of susy parameters relevant for the determination of the relic abundance . the rest of the spectrum is allowed to be heavy , so that our study is very conservative as it considers only ew production of staus and neutral and charged higgsinos . moreover , the atlas collaboration has recently performed a search for new physics in a final state with at least two taus and large missing transverse momentum @xcite , that we will translate into a stringent test of the light neutralino parameter space . at @xmath10 tev , has been presented by cms @xcite . the exclusion limit they obtain seems to be perfectly compatible with the results of ref . @xcite . ] the rest of this paper is organized as follows . in section [ sec : lightdm ] we qualitatively review the features of the parameter space compatible with light neutralino dm and we define the simplified model we are going to employ in the rest of the study . a quantitative discussion of the relevant constraints and the result of a numerical scan of the parameter space are presented in section [ sec : relicdensity ] , while bounds from direct and indirect dark matter searches are briefly discussed in [ sec : dmsearches ] . section [ sec : lhc_pheno ] is dedicated to a discussion of the spectrum of the light dm scenario and the consequences for susy searches at the lhc . in section [ sec : otherlhc ] , we discuss the indirect limits on the parameter space from invisible higgs decays and we show the possible impact of direct dm searches at the lhc in the monojet plus missing energy channel . in section [ sec : lhc_numerics ] , we present a monte carlo study reproducing the limits from ref . afterwards we translate these limits into bounds on the light neutralino parameter space . we conclude summarizing our results in section [ sec : conclusions ] .

we investigate the current status of the light neutralino dark matter scenario within the minimal supersymmetric standard model ( mssm ) taking into account latest results from the lhc . we reinterpret a recent search for electroweak supersymmetric particle production based on a signature including multi - taus plus missing transverse momentum performed by the atlas collaboration . in this way we derive stringent constraints on the light neutralino parameter space . in combination with further experimental information from the lhc , such as dark matter searches in the monojet channel and constraints on invisible higgs decays , we obtain a lower bound on the lightest neutralino mass of about . , light neutralino dark matter can be fully tested up to about . ulb - th/13 - 10 , mpp-2013 - 162 , stupp-2013 - 213 * cornering light neutralino dark matter at the lhc * + lorenzo calibbi , jonas m. lindert , toshihiko ota , yasutaka takanishi + _ service de physique thorique , universit libre de bruxelles , _ _ bld du triomphe , cp225 , b-1050 brussels , belgium _ _ _ department of physics , saitama university , _ _ shimo - okubo 255 , 338 - 8570 saitama - sakura , japan _

we investigate the current status of the light neutralino dark matter scenario within the minimal supersymmetric standard model ( mssm ) taking into account latest results from the lhc . a discussion of the relevant constraints , in particular from the dark matter relic abundance , leads us to a manageable simplified model defined by a subset of mssm parameters . within this simplified model we reinterpret a recent search for electroweak supersymmetric particle production based on a signature including multi - taus plus missing transverse momentum performed by the atlas collaboration . in this way we derive stringent constraints on the light neutralino parameter space . in combination with further experimental information from the lhc , such as dark matter searches in the monojet channel and constraints on invisible higgs decays , we obtain a lower bound on the lightest neutralino mass of about . this limit is stronger than any current limit set by underground direct dark matter searches or indirect detection experiments . with a mild improvement of the sensitivity of the multi - tau search , light neutralino dark matter can be fully tested up to about . ulb - th/13 - 10 , mpp-2013 - 162 , stupp-2013 - 213 * cornering light neutralino dark matter at the lhc * + lorenzo calibbi , jonas m. lindert , toshihiko ota , yasutaka takanishi + _ service de physique thorique , universit libre de bruxelles , _ _ bld du triomphe , cp225 , b-1050 brussels , belgium _ _ max - planck - institut fr physik ( werner - heisenberg - institut ) , _ _ fhringer ring 6 , d-80805 mnchen , germany _ _ department of physics , saitama university , _ _ shimo - okubo 255 , 338 - 8570 saitama - sakura , japan _ _ max - planck - institut fr kernphysik , _ _ saupfercheckweg 1 , d-69117 heidelberg , germany _

1103.1058

c

since gravity is of scale free , it is generally believed that in the scenario of hierarchical clustering , the formation and evolution of halos is scale free in a large range of halo mass . however , the dynamics of the system consisting of two components , dark matter and igm , is very different from those of one component system . in the nonlinear regime , the hydrodynamical nature of the igm leads to the dynamical and statistical departure of the igm from the dark matter . the two component system is no longer to follow the scaling of gravitational clustering of pure dark matter . this deviation is a reason of the baryon missing in gravitational collapsed halos . the dynamical equation of vorticity does not contain terms of gravity . therefore , the igm turbulence characterized by the vorticity will yield , at least , two scales , which violate the scale free of the gravitational hierarchical clustering : 1 . ) the length scale on which the igm fluid has been developed to the state of fully developed turbulence ; 2 . ) the mass scale on which the turbulence pressure is comparable with gravity of halo considered . these scales play important role in the evolution of baryon fraction . with cosmological hydrodynamic simulation , we find that at @xmath99 the first scale is about 3 h@xmath3 mpc , and the second one is @xmath169 h@xmath3 m@xmath4 . with these results , we reach to the following conclusions : \i . the distribution of baryon fraction is highly nonuniform on scales from hundreds kpc to a few of mpc , and @xmath0 varies from as low as 1% to a few times of the cosmic mean . the turbulence can effectively prevent the igm from falling into potential wells of dark matter halos with mass @xmath169 h@xmath3 m@xmath4 . the @xmath0 in dark matter halos is decreasing from @xmath201 at halo mass scales around @xmath6 @xmath7 m@xmath4 to @xmath8 at @xmath2 h@xmath3 m@xmath4 due to the turbulent state of the igm . the estimated turbulence pressure at @xmath99 correspond to a random motion with r.m.s velocity of about @xmath202 km @xmath203 in the scale range from hundreds of kpc and up to @xmath204 mpc . the turbulent pressure is dynamical and non - thermal . when the turbulence dissipated , its kinetic energy becomes the thermal energy . it yields the entropy in halos ( he , feng , & fang 2005 ) . therefore , the dissipation of turbulence actually is a mechanism of heating , which gives a compensation to the cooling of gas in halos . this result is consistent with the burgers shock heating ( he et al 2004 ) . in summmary , the dynamics of turbulence can effectively affect the baryon fraction of halos .

we find that the distribution of baryon fraction is highly nonuniform on scales from hundreds kpc to a few of mpc , and varies from as low as 1% to a few times of the cosmic mean . numerical results show that is decreasing from at halo mass scales around m to at h m and shows further decrease when halo mass is less than h m .

we investigate the dynamical effect of the turbulence in baryonic intergalactic medium ( igm ) on the baryon fraction distribution . in the fully developed nonlinear regime , the igm will evolve into the state of turbulence , containing strong and curved shocks , vorticity and complex structures . turbulence would lead to the density and velocity fields of the igm to be different from those of underlying collisionless dark matter . consequently , the baryon fraction will deviate from its cosmic mean . we study these phenomena with simulation samples produced by the weighted essentially non - oscillatory ( weno ) hybrid cosmological hydrodynamic / n - body code , which is effective of capturing shocks and complex structures . we find that the distribution of baryon fraction is highly nonuniform on scales from hundreds kpc to a few of mpc , and varies from as low as 1% to a few times of the cosmic mean . we further show that the turbulence pressure in the igm is weakly scale - dependent and comparable to the gravitational energy density of halos with mass around h m . the baryon fraction in halos with mass equal to or smaller than h m should be substantially lower than . numerical results show that is decreasing from at halo mass scales around m to at h m and shows further decrease when halo mass is less than h m . the strong mass dependence of is similar to the observed results . although the simulated in halos are higher than the observed value by a factor of 2 , the turbulence of the igm should be an important dynamical reason leading to the remarkable missing of baryonic matter in halos with mass h m . [ firstpage ] cosmology : theory - intergalactic medium - large - scale structure of the universe - methods : numerical

1306.2178

r

let us begin with a brief review of the earlier results based on which we will continue to explore similar physical effects in our current work . before taking any back - reaction into account , the model we consider is described in @xcite . the authors introduced probe d7/anti - d7 branes in the ads@xmath14 background , which is obtained as the near - horizon limit of a stack of d3-branes placed at the tip of the conifold . the d7/anti - d7 branes wrap a @xmath15-cycle in the internal manifold @xmath16 and are extended along the rest of the conifold . before introducing the flavours , the dual field theory is given by an @xmath17 superconformal quiver gauge theory in @xmath18-dimensions with a gauge group @xmath19 and a global @xmath20 symmetry group . the degrees of freedom are contained in two bi - fundamental chiral superfields which transform in the @xmath21 and @xmath22 representations of the gauge group . introducing the probe branes corresponds , in the dual field theory , to introducing flavour degrees of freedom in an analogue of the so called quenched approximation " . this amounts to introducing a global @xmath23 flavour symmetry group , where @xmath24 denotes the number of flavours . the zero temperature physics of this system captures a geometric realization of the spontaneous breaking of chiral symmetry : the brane anti - brane pair joins in the ir breaking the aforementioned flavour symmetry group down to a diagonal @xmath25 . on the other hand , the finite temperature physics of this system is rather trivial : since the background is conformal , there is no scale in the system and hence no phase transition can happen . chiral symmetry is always restored in this case @xcite . nonetheless , the system exhibits interesting phase structure and some interesting phenomenon , such as the effect of _ magnetic catalysis _ in chiral symmetry breaking , when more control parameters are introduced @xcite . in this article we will analyze the effect of the back - reaction by flavours on the physics observed and analyzed in @xcite . towards that end , we need to find the back - reacted background . such a background can be found by sourcing the supergravity equations of motion by the dirac - born - infeld ( dbi ) contribution coming from the probe flavour degrees of freedom . it turns out that , employing the smearing technique " , we can find an analytical solution of these back - reacted equations of motion at the leading order in the @xmath11 correction @xcite . in einstein frame , the most general form of the back - reacted background is given by @xmath26 \ , \\ f_5 & = & k(r ) h(r)^{3/4 } \left ( e^t \wedge e^{x^1 } \wedge e^{x^2 } \wedge e^{x^3 } \wedge e^r + e^{\psi } \wedge e^{\theta_1 } \wedge e^{\phi_1 } \wedge e^{\theta_2 } \wedge e^{\phi_2 } \right ) \ , \end{aligned}\ ] ] where the vielbeins are given by @xmath27 here @xmath28 is a function that we can determine from the relation @xmath29 where @xmath30 is the string coupling defined at @xmath31 , which is a uv cut - off that we need to introduce since we have a running dilaton ; @xmath32 is the string length and @xmath33 is the ads - radius . the various metric functions are given by @xmath34 \ , \\ & & e^{g(r ) } = r \left [ 1 + \epsilon \left ( -\frac{1}{48 } - \cm^{-2 } \left(\frac{r_h^4}{r^2}\right ) k \left ( 1 - \frac{r_h^4}{r^4}\right ) + 2 \cm^{-2 } r^2 e \left(1 - \frac{r_h^4}{r^4}\right ) \right)\right ] \ , \label{solg}\end{aligned}\ ] ] with @xmath35 here @xmath36 is the location of the event - horizon , @xmath37 and @xmath38 are two constants which correspond to in the dual field theory the couplings of a dimension @xmath12 and a dimension @xmath13 operator , respectively . is denoted by @xmath39 in @xcite . the general solution in @xcite contains another constant which is denoted by @xmath40 ; however , since the coupling corresponding to the dimension @xmath13 operator is a linear combination of these two constants , we have set @xmath41 without the loss of any generality . ] note that the relevant physical coupling should be defined at the temperature scale . however , for our background this relation takes the form @xmath42 + \co(\epsilon^2 ) \ , \label{lambdath}\end{aligned}\ ] ] which yields @xmath43 . since the background in ( [ solb])-([solg ] ) is valid up to @xmath44 , we have @xmath45 . the temperature of the background can be identified with the inverse period of the euclidean time direction . this yields @xcite , @xmath46 before proceeding further , let us comment on the regime of validity of the solution given in ( [ solb])-([solg ] ) . to avoid the landau pole coming from the diverging dilaton field we need to impose @xmath47 , where @xmath48 is the uv cut - off . now the perturbative solution for various other functions will hold provided @xmath49 in @xcite , we have explored the phase diagram of an additional probe sector in the background given in ( [ backmet ] ) and ( [ solb])-([solg ] ) imposing @xmath50 , _ i.e. _ setting the source for the dimension @xmath13 operator to zero . the inclusion of the back - reaction breaks the conformal invariance of the background and we found that the additional probe sector now undergoes a chiral phase transition . this phase transition is , in a very precise sense , caused by the existence of the landau pole : this pole is located at @xmath51 at the leading order in @xmath52 , which means we need to use a momentum uv cut - off . in what follows , we will discuss the phase structure in the additional probe sector including more control parameters such as a constant electro - magnetic field . before going further , let us revisit the phase structure in more details . following @xcite , we introduce @xmath53 additional probe d7 and anti - d7 branes such that @xmath54 . these @xmath53 probes are aligned in a way similar to the back - reacting flavour branes . the dynamics of the @xmath53 flavours are given by @xmath55 where @xmath56 is the tension of the probe , @xmath57 denotes the volume along the three spatial directions and @xmath58 is the background temperature . we have denoted @xmath59 and also used the fact that it is consistent to set @xmath60 . the equation of motion admits two classes of solutions : the parallel - shaped solutions denoted by @xmath61 and the u - shaped solutions given by @xmath62 where @xmath63 is the point where the brane anti - brane pair joins smoothly . the parallel - shaped solutions correspond to the chiral symmetry restored phase and the u - shaped solutions correspond to the chiral symmetry broken phase . before discussing the phase transition , let us comment on the dependence of the coupling @xmath64 on the expansion parameter @xmath52 . for @xmath65 , the asymptotic angular separation is given by @xmath66 thus at the leading order in @xmath52 the angular separation decreases linearly with @xmath52 with a slope which is determined by @xmath63 and @xmath36 . the dependence of @xmath64 with @xmath52 is schematically shown in fig . [ phir0 ] . it is clear that , for the u - shaped profiles , increasing the effect of the back - reaction reduces the maximum value attained by the angular separation , denoted by @xmath67 . and @xmath68 respectively corresponding the u - shaped embeddings . we have set @xmath69 and @xmath70 and @xmath71 . the solid vertical blue line correspond to the parallel embeddings . ] in fact there is more physics in fig . [ phir0 ] : it displays the various available phases of the system for a given value of the coupling @xmath64 . for any @xmath72 , we only have the chiral symmetry restored phase available . on the other hand , for any @xmath73 , we have three available points in the phase space : one on the vertical solid line and two on the dashed curves . comparing this situation with the more familiar @xmath74-diagram of the van der waals gas , we can conclude that there exists a first order phase transition from a point on the solid vertical line ( _ i.e. _ the chiral symmetry restored phase ) to a point on the dashed line ( _ i.e. _ the chiral symmetry broken phase ) for some critical value of @xmath64 . the energetics of the two classes of embeddings will now decide the phase of the system . one has to look at the euclidean on - shell action which is identified with the thermodynamic free energy of the system for these two types of embeddings and compute their difference @xmath75 now depending whether @xmath76 or @xmath77 , we will get a chiral symmetry restored or a chiral symmetry broken phase . this results in a non - trivial phase structure analyzed in @xcite , which we have shown in fig . [ figphase ] . the phase diagram is presented in the @xmath64 vs @xmath78 plane , where @xmath78 is defined as @xmath79 vs @xmath78 plane . the blue line separates the @xmath80sb @xmath81 chiral symmetry broken phase ( below the line ) from the @xmath80sr @xmath81 chiral symmetry restored phase ( above the line ) . between the blue and the red line , we also have a metastable @xmath80sb phase . above the red line we have only the @xmath80sr phase . ] we want to emphasize two main features here : first , in the absence of the back - reaction , no such phase structure exists at finite temperature . the underlying theory is conformal and only the chiral symmetry restored phase exists . taking back - reaction into account breaks the conformal invariance by introducing a uv landau pole and also deforming the cft by higher dimensional irrelevant operators . in the leading order back - reacted solution described here , the uv landau pole is located at @xmath51 and the couplings corresponding to the irrelevant operators of dimension @xmath12 and @xmath13 respectively are denoted by @xmath37 and @xmath82 . from the phase diagram shown in fig . [ figphase ] it is clear that @xmath83 is not a special point as far as the existence of the phase transition is considered . thus we can conclude that the non - trivial phase structure and the associated thermodynamics that we obtain in this back - reacted model is caused by the existence of the landau pole . we will now move on to discuss the effect of the back - reaction on some bulk properties of the background as well as the phase structure of an additional probe sector in the spirit of @xcite .

we investigate the effect of the back - reaction by non - supersymmetric probes in the kuperstein - sonnenschein model . in the limit where the back - reaction is small , we find that the landau pole , which serves as the uv cut - off of the background geometry , also serves as an important scale in the corresponding thermodynamics of the additional flavour sector . we note that since these additional probe flavours are indistinguishable from the back - reacting flavours , the results we obtain point to a much richer phase structure of the system .

we investigate the effect of the back - reaction by non - supersymmetric probes in the kuperstein - sonnenschein model . in the limit where the back - reaction is small , we discuss physical properties of the back - reacted geometry . we further introduce additional probe flavours in this back - reacted geometry and study in detail the phase structure of this sector when a constant electromagnetic field or a chemical potential are present . we find that the landau pole , which serves as the uv cut - off of the background geometry , also serves as an important scale in the corresponding thermodynamics of the additional flavour sector . we note that since these additional probe flavours are indistinguishable from the back - reacting flavours , the results we obtain point to a much richer phase structure of the system . = 10000 dias - stp-13 - 04 + uttg-15 - 13 + tcc-011 - 13 * dynamics of non - supersymmetric flavours * * m. sohaib alam , matthias ihl , arnab kundu and sandipan kundu * theory group , department of physics university of texas at austin austin , tx 78712 , usa . school of theoretical physics dublin institute for advanced studies 10 burlington rd , dublin 4 , ireland . texas cosmology center university of texas at austin austin , tx 78712 , usa . msihl[at]stp.dias.ie , malam , arnab , sandyk[at]physics.utexas.edu

1007.2499

i

scalar field theories have become generic playgrounds for building cosmological models related to particle physics @xcite , and more recently , have played very important contributions in the other branches of cosmology , e.g. , as a powerful tool for providing expanding accelerated universes . also , they have key roles in some models of the early cosmological inflation @xcite , and are viable favorite candidates for dark matter @xcite . indeed , scalar field cosmological models have extensively been studied in the literature , see , e.g. , refs . @xcite and references therein . unifying theories of interactions , such as the kaluza klein , supergravity and superstring theories , usually predicts non minimal couplings between geometry of space time and scalar fields . these theories mostly are derived from effective actions of string theories @xcite or from compactified kaluza klein theories in four dimensions @xcite . in both cases , resulting models have non minimal couplings between gravity and one ( or even more ) scalar field . actually , considering more than one scalar field has been viewed as an easier approach to study accelerating models . these cosmological ideas have also been employed in models of inflation to describe the early universe @xcite or an evolving scalar field known as quintessence @xcite . recently , double scalar tensor theories have been applied in extended gravitational theories , and have given successful descriptions of inflationary scenarios @xcite . besides , it has been shown @xcite that the reduction of a five dimensional brans dicke gravity into four dimensions is equivalent to a 4metric coupled to two scalar fields , which may account for the present accelerated expansion of the universe . also , effects of additional scalar fields plus independent exponential potentials have been considered in the literature @xcite . in cosmological models , scalar fields usually present degrees of freedom and appear as dynamical variables of corresponding minisuperspaces . this point can be viewed as relevance of noncommutativity in these models . the proposal of noncommutativity concept between space time coordinates , in the first time , was introduced in 1947 @xcite . thereafter , a mathematical theory , nowadays known as the noncommutative geometry ( * ncg * ) , has begun to take shape based on this concept since 1980 @xcite . noncommutativity among space time coordinates implies noncommutativity among fields as minisuperspace coordinates . such a kind of noncommutativity has gotten more attention in the literature . in the last decade , study and investigation of physical theories in the noncommutative ( * nc * ) frames , such as the string and m theory @xcite , have caused a renewed interest on noncommutativity in the classical and quantum perspectives . in particular , a novel interest has been developed in studying the nc classical and quantum cosmologies , e.g. refs . @xcite and references therein . also , deformation of the phase space structure has been viewed as an alternative path , in the context of cosmology , toward understanding quantum gravity @xcite . the influence of noncommutativity has been examined by formulation of a version of the nc cosmology in which a deformation of the minisuperspace coordinates @xcite@xcite or the minisuperspace momenta @xcite is required instead of the space time coordinates . from a qualitative point of view , noncommutativity in the minisuperspace coordinates ( space sector ) leads to general effects , however , a non trivial noncommutativity in the momentum sector introduces distinct and instructive effects in the behavior of dynamical variables . in this work , we consider homogeneous and isotropic cosmological models based on a particular ( multi)scalar tensor gravity theory with two scalar fields that have non minimal conformal couplings to the space time . the effects of noncommutativity on the phase space , generated by these fields plus the scale factor , are investigated . our approach is to build a nc scenario via a deformation conveyed by the moyal product @xcite in a classical and a quantum perspective , where their cosmological implications are more appreciated in the classical one . the procedure of quantization is proceeded by the wheeler dewitt ( * wd * ) equation for a wave function of the universe by the hamiltonian operator of the model via the generalized dirac quantization . we introduce noncommutativity between the scalar fields and between their canonical conjugate momenta , and will pay more attention to the outcome of results . here , we neglect noncommutativity between scalar fields with the scale factor , such effects can be found in , e.g. , refs . actually we treat the effects of noncommutativity by two parameters which are the nc parameters corresponding to the space and momentum sectors . then , we analyze the mathematical properties of solutions and look for relations , including the ranges and values , among the nc parameters for which particular or allowed solutions exist . the manuscript is organized as follows . in section @xmath0 , we specify our toy model and investigate the classical version within the commutative and nc frames . the quantum version of this model , by probing the universe wave functions , is considered in section @xmath1 , where the general properties of solutions in the commutative and nc frames are compared . in section @xmath2 , we employ the noether theorem and explore the effects of noncommutativity on the underlying symmetries in the commutative frame . conclusions are presented in the last section , and some necessary formulations have been furnished in the appendix .

we investigate the effects caused by noncommutativity of the phase space generated by two scalar fields that have non minimal conformal couplings to the background curvature in the frw cosmology . furthermore , the noether theorem has been employed to explore the effects of noncommutativity on the underlying symmetries in the commutative frame .

we investigate the effects caused by noncommutativity of the phase space generated by two scalar fields that have non minimal conformal couplings to the background curvature in the frw cosmology . we restrict deformation of the minisuperspace to noncommutativity between the scalar fields and between their canonical conjugate momenta . then , the investigation is carried out by means of a comparative analysis of the mathematical properties ( supplemented with some diagrams ) of the time evolution of variables in a classical model and the wave function of the universe in a quantum perspective , both in the commutative and noncommutative frames . we find that the impose of noncommutativity causes more ability in tuning time solutions of the scalar fields and hence , has important implications in the evolution of the universe . we get that the noncommutative parameter in the momenta sector is the only responsible parameter for the noncommutative effects in the spatially flat universes . a distinguishing feature of the noncommutative solutions of the scalar fields is that they can be simulated with the well known three harmonic oscillators depending on three values of the spatial curvature . namely the free , forced and damped harmonic oscillators corresponding to the flat , closed and open universes , respectively . in this respect , we call them _ cosmical oscillators_. in particular , in closed universes , when the noncommutative parameters are small , the cosmical oscillators have analogous effect with the familiar beating effect in the sound phenomena . some of the special solutions in the classical model and the allowed wave functions in the quantum model make bounds on the values of the noncommutative parameters . the existence of a non zero constant potential ( i.e. a cosmological constant ) does not change time evolutions of the scalar fields , but modifies the scale factor . an interesting feature of well behaved solutions of the wave functions is that the functional form of the radial part is the same as the commutative ones within a given replacement of constants caused by the noncommutative parameters . furthermore , the noether theorem has been employed to explore the effects of noncommutativity on the underlying symmetries in the commutative frame . two of the six noether symmetries of spatially flat universes , in general , are retained in the noncommutative case , and one out of the three ones in non flat universes . -2.4 cm

1007.2499

c

we have carried out an investigation for the role of ncg in cosmological scenarios , based on a four dimensional free potential ( multi)scalar tensor action of gravity , by introducing a nc deformation in the minisuperspace variables . the phase space is generated by two non interacting conformal scalar fields plus the scale factor with their canonical conjugate momenta . the scalar fields are non minimally coupled to geometry whose background is the frw metric , where the conformal time gauge evolutions have been studied . the noncommutativity has been introduced only between the scalar fields and between their canonical conjugate momenta via two nc parameters @xmath78 and @xmath79 , respectively . the investigation has been carried out for this toy model by means of a comparative mathematical analysis of the time evolution of the dynamical variables in the classical level and of the wave function of the universe in the quantum perspective , both in the commutative and nc frames . we have paid more attention to the outcome of results and have looked for the relations , including ranges and values , among the nc parameters for which particular or allowed solutions exist . in general , we have shown by this toy model that the purposed noncommutativity has important implications in the evolution of the universe , however , does not affect the time dependence of the scale factor , i.e. its solution is the same as the commutative case , as expected . also , we have found that one of the particularity of the nc parameter in the momenta sector , i.e. @xmath79 , is in the spatially flat frw universe , where it is the only responsible parameter for the nc effects in the classical and quantum frames . in the classical model , exact solutions have been obtained . one of the important aspects of the nc solutions is that they can be regulated with both nc parameters . for example , these parameters can be employed to adjust the time dependence of solutions with the experimental or observational data . a distinguished feature of the noncommutativity effects , which we call a cosmical oscillator , is that the scalar fields behave similar to ( or can be simulated with ) the three most important harmonic oscillators depending on three values of the spatial curvature . these are the free , forced and damped harmonic oscillators corresponding to the flat , closed and open universes , respectively . in the flat universes , the time dependence of solutions are modified from linear in the commutative case to periodic in the nc frame . in the closed universes , if the ration of frequencies of the scalar fields is a rational fraction , then solutions will be periodic . this condition restricts the nc parameters . when this ratio is not a rational fraction , the solutions are non periodic but their behaviors still depend on the values of the nc parameters . a plot with numerous ( or a few ) relative extremum in a given time interval indicates that the separation between the high and low points increases when the nc parameters tend to smaller values , and this property is intensified for values less than unity . from this point of view , the nc solutions have particular preference with respect to the corresponding commutative ones . furthermore , in the @xmath108 case , the solutions are symmetric with respect to the nc parameters , and the results do not vary by replacement of their roles . also , when the nc parameters are small , the cosmical oscillators have analogous effects with the familiar beating effects in the sound phenomena . for a better view on this situation , an example has been illustrated in the text . in the open universes , there are upper and lower bounds on the nc parameters . the quick and late damping of this case can be adjusted by the nc parameters . for example , for @xmath328 and @xmath329 , the scalar fields have maximum number of oscillations before the complete damping occurs . we have also shown that the existence of a non zero constant value of the potential function ( i.e. the cosmological constant ) does not change the time evolutions of the scalar fields , but it modifies the time dependence of the scale factor in a same manner for both the commutative and nc frames . indeed , we have obtained that in all allowed conditions the scale factor behaves as a sinusoidal function . in the quantum model , the exact solutions for the wave functions of the universe have also been obtained . the scale factor part of the wave function is similar to its commutative analog , as expected . one still expects that when the noncommutativity effects are turned on in the quantum scenario , they should introduce significant modifications in the scalar fields . however , an interesting feature of the well behaved solutions is that the functional form of the radial part of the nc wave function is the same as the commutative ones within the given replacements of constants caused by the nc parameters , although these replacements in turn may cause drastic effects . for example , the curvature index is modified , and in open universes , the allowed nc wave functions impose bounds on the nc parameters . finally , we have employed the noether theorem and have explored the effects of noncommutativity on the underlying symmetries in the commutative frame . we have shown that for spatially flat universes , there are six noether symmetries , and , in general , only two of them are retained in the nc case . in the special case @xmath305 , all symmetries survive regardless of the existence of @xmath78 parameter . for non flat universes , there are three noether symmetries in the commutative case , one of which is retained in the nc frame . however , in open universes , when the nc parameters have the values @xmath323 , the number and general form of symmetries do not change with respect to the commutative frame . the only difference is related to the sign of symmetries . conservation of the angular momentum about the scale factor axis is a common face between the commutative and nc cases , as expected in the purposed noncommutativity . we should emphasis that the scalar fields solutions are given after rescalings of the original fields , relations ( [ rescalingfields ] ) , and in the conformal time . consequently , the functional forms of the solutions are not as simple when translated to the original fields . however , any detection should be performed in a reference frame , and there are debates on the physical frame in the cosmological contexts . besides , the model is to be taken as a toy model only that still provides a valuable contribution to the assessment of the implications of the nc geometrical deformations of the phase space upon the dynamics of the cosmological model envisaged . however , a more realistic nc cosmological model may be achieved when one also involves the noncommutativity of the scalar fields with the scale factor , where the value of its time derivative in the form of the hubble parameter can be determined from observations .

we restrict deformation of the minisuperspace to noncommutativity between the scalar fields and between their canonical conjugate momenta . then , the investigation is carried out by means of a comparative analysis of the mathematical properties ( supplemented with some diagrams ) of the time evolution of variables in a classical model and the wave function of the universe in a quantum perspective , both in the commutative and noncommutative frames . we find that the impose of noncommutativity causes more ability in tuning time solutions of the scalar fields and hence , has important implications in the evolution of the universe . we get that the noncommutative parameter in the momenta sector is the only responsible parameter for the noncommutative effects in the spatially flat universes . a distinguishing feature of the noncommutative solutions of the scalar fields is that they can be simulated with the well known three harmonic oscillators depending on three values of the spatial curvature . namely the free , forced and damped harmonic oscillators corresponding to the flat , closed and open universes , respectively . in this respect , we call them _ cosmical oscillators_. in particular , in closed universes , when the noncommutative parameters are small , the cosmical oscillators have analogous effect with the familiar beating effect in the sound phenomena . the existence of a non zero constant potential ( i.e. a cosmological constant ) does not change time evolutions of the scalar fields , but modifies the scale factor . an interesting feature of well behaved solutions of the wave functions is that the functional form of the radial part is the same as the commutative ones within a given replacement of constants caused by the noncommutative parameters .

we investigate the effects caused by noncommutativity of the phase space generated by two scalar fields that have non minimal conformal couplings to the background curvature in the frw cosmology . we restrict deformation of the minisuperspace to noncommutativity between the scalar fields and between their canonical conjugate momenta . then , the investigation is carried out by means of a comparative analysis of the mathematical properties ( supplemented with some diagrams ) of the time evolution of variables in a classical model and the wave function of the universe in a quantum perspective , both in the commutative and noncommutative frames . we find that the impose of noncommutativity causes more ability in tuning time solutions of the scalar fields and hence , has important implications in the evolution of the universe . we get that the noncommutative parameter in the momenta sector is the only responsible parameter for the noncommutative effects in the spatially flat universes . a distinguishing feature of the noncommutative solutions of the scalar fields is that they can be simulated with the well known three harmonic oscillators depending on three values of the spatial curvature . namely the free , forced and damped harmonic oscillators corresponding to the flat , closed and open universes , respectively . in this respect , we call them _ cosmical oscillators_. in particular , in closed universes , when the noncommutative parameters are small , the cosmical oscillators have analogous effect with the familiar beating effect in the sound phenomena . some of the special solutions in the classical model and the allowed wave functions in the quantum model make bounds on the values of the noncommutative parameters . the existence of a non zero constant potential ( i.e. a cosmological constant ) does not change time evolutions of the scalar fields , but modifies the scale factor . an interesting feature of well behaved solutions of the wave functions is that the functional form of the radial part is the same as the commutative ones within a given replacement of constants caused by the noncommutative parameters . furthermore , the noether theorem has been employed to explore the effects of noncommutativity on the underlying symmetries in the commutative frame . two of the six noether symmetries of spatially flat universes , in general , are retained in the noncommutative case , and one out of the three ones in non flat universes . -2.4 cm

astro-ph9911233

i

the integrated light of elliptical galaxies contains many clues to their star formation histories . currently , the most popular approach to deciphering the broad band colors and spectral features of elliptical galaxies and star clusters is evolutionary population synthesis ( charlot & bruzual 1991 ; bressan , chiosi , & fagotto 1994 ; worthey 1994 ) . this technique models the integrated light for a stellar population of a given age and metallicity by summing up the light from individual stars along theoretical isochrones . the resulting spectral energy distribution ( sed ) is dependent on the libraries of stellar evolutionary tracks and stellar fluxes , the chosen star formation rate and initial mass function ( imf ) , and in the case of multi - metallicity populations , the chemical enrichment history . charlot , worthey , & bressan ( 1996 ) examined the differences between several recent models and found that they are seriously limited by the dearth of reliable libraries for cool and non - solar composition stars and by the uncertain properties of post main sequence stars . nevertheless , population synthesis is appealing because of its ability to prescribe a fundamental recipe for a galaxy . attempts to unravel the history of star formation in elliptical galaxies via spectral synthesis are plagued by the `` age - metallicity degeneracy '' ( worthey 1994 and references therein ) . the effective temperature of the red giant branch ( rgb ) decreases with increasing age and metallicity in such a way that the rgb of an old solar metallicity population looks nearly identical to that of a more metal - rich , slightly younger population . because the rgb dominates both the integrated line strength and broad band color longward of 4000 , a degeneracy of these properties in age and abundance results for stellar populations older than 1 gyr . the most promising attempts to disentangle age and metallicity from integrated spectra have involved use of the balmer absorption lines @xcite and mid - uv colors ( dorman , oconnell , & rood 1995 ) . all of these methods rely on spectral diagnostics for which the main sequence begins to dominate over the rgb . the contribution of the main sequence turn - off to the integrated light is greatest in the mid - uv region ( @xmath5 2500 - 3500 ) ; the contribution of the far - uv bright hb and post hb stars to the integrated light is less than 50% at 2500 ( worthey , dorman , & jones 1996 ) . @xcite suggest that the spectral break at 2900 is correlated with spectral type of the turn - off population but weakly influenced by metallicity . also , the continuum of mid - uv is affected by the metallicity of the stellar population . @xcite found that the color ( 2500-v ) was correlated with metallicity and fanelli et al . ( 1990 , 1992 ) found @xmath6 ( 2600-v ) 10 times more sensitive to [ fe / h ] than @xmath6 ( b - v ) . because the spectral type of the main sequence turn - off stars dominates the absorption features of the mid - uv and the continuum is highly sensitive to chemical content , a detailed investigation of the integrated mid - uv light of stellar populations may help break the age - metallicity degeneracy . one observational result population synthesis models have sought to explain is the correlation between the `` uv upturn '' shortward of 2000 and the optical mg@xmath0 absorption line strength in elliptical galaxies @xcite . the brightest galaxies in uv also have the strongest mg@xmath0 absorption ( burstein et al . 1988 ) , suggesting that these uv strong galaxies are metal - rich and possibly enhanced in @xmath7 element abundances . in the most metal - rich galaxies , the primary source of far - uv emission appears to be extreme horizontal branch ( ehb ) stars and their descendants , the agb - manqu stars . while the bulk of the evidence favors a metal - rich origin for the ehb stars @xcite , models with a distribution of metallicities including a metal - poor tail @xcite can not be excluded . in any case , the models for hot populations are strongly dependent on mass loss on the red giant branch and on the helium abundance . small changes in these two parameters can give wildly different uv upturns at fixed age and metallicity . for the purposes of this paper , the uv upturn is simply an underlying continuum that must be subtracted from the galaxy spectra prior to analysis of the spectral features . the star formation history of nearby ellipticals , particularly m32 , has been in the subject of much debate . in 1980 , @xcite proposed that a 5 gyr stellar sub - population is responsible for the relatively blue @xmath8 color of m32 . the idea that m32 contains a large intermediate age population was supported by detailed comparison of m32 and 47 tuc ( an old `` metal - rich '' globular cluster ) near uv spectra ( 3800 - 4400 ) @xcite . the study of h@xmath9 and h@xmath10 absorption lines , which are dependent on the main sequence turn - off stars in old stellar populations , suggest intermediate ages for many ellipticals @xcite . however , recent hst observations of m32 s red giant branch implies that at least half of m32 s stars are older than 8 gyr @xcite . the metallicity distribution of m32 and other ellipticals has also been investigated . @xcite found evidence for a hot metal - poor population in an otherwise metal - rich population in the mid - uv spectra of m32 . the width of m32 s rgb requires that the stars span a substantial range in metallicity @xcite . the estimated metallicity distribution has a low metallicity tail extending down to [ fe / h ] = -1.5 but is strongly skewed to solar metallicity and is much narrower than expected from a closed box chemical enrichment scenario . comparisons to synthetic spectra suggest that other galaxies , including ngc 1404 , ngc 4649 , and the bulge of m31 , also show a deficit of low metallicity stars relative to closed box models @xcite . the ages of distant elliptical galaxies has been the subject of some debate as well . @xcite determined an age of @xmath5 3.5 gyr ( assuming a solar metallicity ) for lbds 53w091 ( z @xmath5 1.55 ) by comparing the rest frame mid - uv spectral features to solar metallicity f and g stars and population synthesis models . a galaxy this old at a redshift of 1.55 would rule out a @xmath11 , @xmath12 , @xmath13 universe . a later comparison of this galaxy s spectra to improved f star models gave an age of 1 - 2 gyr ( assuming z @xmath14 @xmath15 ) , relaxing the cosmological constraints ( heap et al . because galaxies with 0.5 @xmath2 z @xmath2 1.5 have their mid - uv spectra redshifted into the visible range , a better understanding of the mid - uv features of old stellar populations will be useful for dating distant galaxies . using simple population synthesis models , we examine the mid - uv features and mg@xmath0 strengths of four nearby elliptical galaxies and spiral bulges . in order to study the spectral properties of the underlying main sequence and rgb branch stars , we exclude the uncertain hot hb and post hb stars from our models isochrones and attempt to subtract out the far - uv component from the galaxies spectra . specifically we use the blend feature at 2538 ( bl2538 ) and mg@xmath0 line indices and introduce a new tool for examining the mid - uv continua , the slope between 2600 and 3100 ( @xmath4 ) , to determine the galactic properties . the investigation of the mid - uv dependence on age and abundance via population synthesis is severely limited by inaccuracies in our model stellar fluxes . however , bl2538 and @xmath4 appear to be adequately modeled by the kurucz fluxes . we find for our simple population models that populations older than 3 gyr separate out in the s2850 v. bl2538 and s2850 v. mg@xmath0 planes . although globular cluster spectra agree with simple , single metallicity , single age populations , a small but mid - uv bright component of low metallicity ( z @xmath2 0.001 ) stars may explain the spectral features of ngc 1399 . m32 s uv features can not be explained purely by a significant population of intermediate age ( 1 - 3 gyr ) solar metallicity stars ; a small number of metal - poor stars are suggested by the mid - uv in this case as well . because metal - poor stars are so much brighter than metal - rich stars in the mid - uv , we can not ignore the effects of the metallicity distribution on our population synthesis models . the rest of the paper is arranged as follows : first , in section 2 we test our library of stellar fluxes ( lejeune , cuisnier , & buser 1997 ) for inaccuracies and determine the influence of these inaccuracies on our model spectral energy distributions ( seds ) . in section 3 , we explain our population synthesis models , their mid - uv and optical properties , and compare them to the mid - uv features of several composite globular cluster iue spectra ( bonatto , bica , & alloin 1995 ) . in section 4 , we present the fos spectra of ngc 1399 and ngc 3610 and the iue spectra of ngc 1399 , m32 and the bulge of m31 . we compare our models to these galaxies . in section 5 we examine the effects of a metal - poor sub - population on the integrated spectra of an otherwise metal - rich population .

we investigate the effects of abundance and age on the mid - uv spectra and mg strengths of stellar populations using simple population synthesis models . these models are used to constrain the star formation history of four nearby elliptical galaxies and spiral bulges . the mid - uv ( 1800 - 3200 ) light of evolved stellar populations ( 1 gyr ) is dominated by the main sequence turn - off , unlike the optical light which is dominated by the red giant branch . because the main sequence turn - off is sensitive to age and metallicity in ways different from the rgb , a detailed investigation of the mid - uv features of elliptical galaxies may help break the age - metallicity degeneracy that plagues optical techniques . also , a better understanding of this wavelength region is useful for the studies of 0.5 z 1.5 galaxies for which the rest frame mid - uv is redshifted into the visible . the mid - uv features appear to require both an old metal - rich and an old metal - poor ( z 0.001 ) population . the implied metal - poor population is less than 10% of the total mass for all the galaxies but dominates the seds shortward of 3000 .

we investigate the effects of abundance and age on the mid - uv spectra and mg strengths of stellar populations using simple population synthesis models . these models are used to constrain the star formation history of four nearby elliptical galaxies and spiral bulges . the mid - uv ( 1800 - 3200 ) light of evolved stellar populations ( 1 gyr ) is dominated by the main sequence turn - off , unlike the optical light which is dominated by the red giant branch . because the main sequence turn - off is sensitive to age and metallicity in ways different from the rgb , a detailed investigation of the mid - uv features of elliptical galaxies may help break the age - metallicity degeneracy that plagues optical techniques . also , a better understanding of this wavelength region is useful for the studies of 0.5 z 1.5 galaxies for which the rest frame mid - uv is redshifted into the visible . we create simple , single age ( 3 - 20 gyr ) , single metallicity ( z 0.0004 - 0.05 ) spectral energy distributions ( seds ) extending into the uv using the kurucz model stellar fluxes . comparison to standard stars mid - uv spectra reveals that the kurucz model fluxes accurately model a blend feature of fei and mgi at 2538 ( bl2538 ) and the slope of the continuum between 2600 and 3100 ( ) . we find that our simple single age , single metallicity seds agree well with these mid - uv features of globular clusters . however , the majority of the galaxies do not agree with the bl2538 , , and mg values given by these simple models . the mid - uv features appear to require both an old metal - rich and an old metal - poor ( z 0.001 ) population . the implied metal - poor population is less than 10% of the total mass for all the galaxies but dominates the seds shortward of 3000 . intermediate age ( 1 - 5 gyr ) populations are not required to match the uv for any of the galaxies , but are not ruled out . despite being limited by the quality of the model stellar fluxes , our study has yielded two promising mid - uv spectral diagnostics ( bl2538 and ) and suggests unique and complex star formation histories for elliptical galaxies .

1701.06721

c

the key findings of this study of the inner gaseous disk of three hbe stars , hd76534 , hd216629 and hd114981 , are : * the emission line spectra of all three stars can be adequately reproduced , in terms of both line strength and shape , from a small ( @xmath134 ) , geometrically thin , gaseous circumstellar disk heated solely by the available photoionizing radiation field from the photosphere of central b star . * the equatorial density in the disks varies roughly as @xmath135 . * the size and mass of the emitting disk are @xmath136 and @xmath137 . * the models , however , are not successful in reproducing the line profiles of hi , hei , caii and feii simultaneously based on an equatorial disk density varying as a single power - law with radius . a possible resolution is to consider equatorial density distributions that vary in a more complex way . * the equatorial density distribution of the three stars is the same as found for the hbe b2 star bd+651637 analyzed in paper i , although their disks are approximately a factor of two smaller in outer radius . we note that the current study focused exclusively on line emission from the inner gaseous disk ; however , continuum emission is also expected , at least in principle , either in the near - ir from mostly hydrogen free - free emission or in the uv from hydrogen bound - free emission . it would be important to quantify the expected level of this emission from the disks above to see if this continuum emission can make a significant contribution to either ( 1 ) the near - ir excess of hbe stars , perhaps addressing why the hbe stars seem undersized compared to the predictions of the disk size luminosity correlation found by @xcite , or ( 2 ) the uv excess seen in some hbe stars that does not seem to be able to be reproduced by magnetospheric accretion models @xcite . finally , an important limitation of the current study is that the three hbe stars analyzed here plus bd+651637 of paper i are all group iii herbig ae / be objects according to the @xcite classification , that is , objects with small infrared excesses resembling classical be stars . we intend to extend our current analysis to group i and ii objects that show unambiguous signs of dust in their infrared spectral energy distributions . we are also extending this analysis to both hotter and cooler hbe stars . the authors would like to thank the anonymous referee for many helpful comments . this work is supported by the canadian natural sciences and engineering research council ( nesrc ) through discovery grants to t. a. a. sigut and j. d. landstreet . alecian , e. , wade , g. a. ; catala , c. , folsom , c. , grunhut , j. , donati , j .- f . , petit , p. , bagnulo , s. , marsden , s. c. , ramirez velez , j. c. , landstreet , j. d. , boehm , t. , bouret , j .- c . & silvester , j. , 2008 , coska , 38 , 235a . sigut , t. a. a. , 2011 , in iau symposium 272 : active ob stars : structure , evolution , mass loss , and critical limits , ed . c. neiner , g. wade , g. meynet , & g. peters ( cambridge : cambridge univ . press ) , 426 .

we investigate the physical properties of the inner gaseous disks of the three , hot , herbig b2e stars , hd76534 , hd114981 and hd216629 , by modelling cfht - espadons spectra using non - lte radiative transfer codes . we assume that the emission lines are produced in a circumstellar disk heated solely by the photospheric radiation from the central star in order to test if the optical and near - ir emission lines can be reproduced without invoking magnetospheric accretion . we conclude that the optical emission line spectra of these hbe stars can be qualitatively reproduced by aau , geometrically thin , circumstellar disk of negligible mass compared to the central star in keplerian rotation and radiative equilibrium .

we investigate the physical properties of the inner gaseous disks of the three , hot , herbig b2e stars , hd76534 , hd114981 and hd216629 , by modelling cfht - espadons spectra using non - lte radiative transfer codes . we assume that the emission lines are produced in a circumstellar disk heated solely by the photospheric radiation from the central star in order to test if the optical and near - ir emission lines can be reproduced without invoking magnetospheric accretion . the inner gaseous disk density was assumed to follow a simple power - law in the equatorial plane , and we searched for models that could reproduce observed lines of hi ( h and h ) , hei , caii and feii . for the three stars , good matches were found for all emission line profiles individually ; however , no density model based on a single power - law was able to reproduce all of the observed emission lines . among the single power - law models , the one with the gas density varying as in the equatorial plane of a 25r ( au ) disk did the best overall job of representing the optical emission lines of the three stars . this model implies a mass for the h-emitting portion of the inner gaseous disk of . we conclude that the optical emission line spectra of these hbe stars can be qualitatively reproduced by aau , geometrically thin , circumstellar disk of negligible mass compared to the central star in keplerian rotation and radiative equilibrium .

1112.3198

i

during the development of denotational semantics of programming languages , there was a crucial interest in defining models of computation satisfying particular type equations . for instance , a model of the untyped @xmath1-calculus can be obtained by isolating a _ reflexive _ object ( that is , an object @xmath2 such that @xmath3 ) in a cartesian closed category . in the 80s , some people started to consider the dual problem of finding these equations that must hold in _ every _ model of a given language : they were coined _ type isomorphisms _ by bruce and longo . in @xcite , they exploited a theorem by dezani @xcite giving a syntactic characterization of invertible terms in the untyped @xmath1-calculus to prove that that the only isomorphisms of types present in simply typed @xmath1-calculus with respect to @xmath4 equality are those induced by the equation @xmath5 . later this was extended to handle such things as products @xcite , higher order @xcite , possibly with unit types @xcite , or sums @xcite . the interest in type isomorphisms grew significantly when their practical impact was realized . in @xcite , rittri proposed to search functions in software libraries using their type modulo isomorphism as a key . he also considered the possibilities offered by matching and unification of types modulo isomorphisms @xcite . a whole line of research has also been dedicated to the study of type isomorphisms and their use for search tools in richer type systems ( such as dependent types @xcite ) , along with studies about the automatic generation of the corresponding coercions @xcite . such tools were implemented for several programming languages , let us mention the command line tool ` camlsearch ` written by vouillon for camllight . it is worth noting that even though these tools are written for powerful programming languages featuring complex computational effects such as higher - order references or exceptions , they rely on the theory of isomorphisms in weaker ( purely functional ) languages , such as the second - order @xmath1-calculus with pairs and unit types for ` camlsearch ` . clearly , all type isomorphisms in @xmath1-calculus are still valid in the presence of computational effects ( indeed , the operational semantics are compatible with @xmath4 ) . what is less clear is whether those effects allow the definition of new isomorphisms . however , it seems that syntactic methods deriving from dezani s theorem on invertible terms in @xmath1-calculus can not be extended to complex computational effects . the base setting itself is completely different : the dynamics of terms are no longer defined by reduction rules but by operational semantics , the natural equality between terms is no longer convertibility but observational equivalence , so new methods are required . in @xcite , laurent introduced the idea of applying game semantics to the study of type isomorphisms ( although one should mention the precursor characterization of isomorphisms by berry and curien @xcite in the category of concrete data structures and sequential algorithms ) . exploiting his earlier work on game semantics for polarized linear logic @xcite , he found the theory of isomorphisms for llp from which he deduced ( by translations ) the isomorphisms for the call - by - name and call - by - value @xmath6-calculus . the core of his analysis is the observation that isomorphisms between arenas @xmath7 and @xmath8 in the category @xmath9 @xcite of arenas and innocent strategies are in one - to - one correspondence with _ forest isomorphisms _ between @xmath7 and @xmath8 , so in particular two arenas are isomorphic if and only if their representations as forests are identical up to the renaming of vertices . from the point of view of computational effects this looks promising , since game semantics are known to accommodate several computational effects such as control operators @xcite , ground type @xcite or higher - order references @xcite or even concurrency @xcite in one single framework . moreover , laurent pointed out in @xcite that the main part of his result , namely the fact that each @xmath9-isomorphism induces a forest isomorphism , does not really depend on the innocence hypothesis but only on the weaker _ visibility _ condition . as a consequence , his method for characterizing isomorphisms still applies to programming languages such as idealized algol whose terms can be interpreted as visible strategies @xcite . laurent raised the question whether his result could be proved without the visibility condition , therefore yielding a characterization of isomorphisms in a programming language whose terms have access to higher - order references and hence get interpreted as non - visible strategies @xcite . the contribution of this paper is threefold : _ ( 1 ) _ we give a new and synthetic reformulation of laurent s tools to approach game - theoretically the problem of type isomorphisms , _ ( 2 ) _ we prove laurent s conjecture in the case of finitely branching arenas , allowing us to characterize all type isomorphisms in a finitary ( integers - free ) programming language @xmath0 with higher - order references by the theory @xmath10 presented mentioned in the introduction may seem strange , but is standard in call - by - value @xcite due to the restriction of the @xmath11-rule on values . ] in figure [ equational_theory ] , _ ( 3 ) _ we show however a counter - example to the conjecture when dealing with infinitely branching arenas , and the counter - example yields a non - trivial type isomorphism between the types @xmath12 and @xmath13 in the extension of @xmath0 with natural numbers . so laurent s conjecture , in the general case , is false . in section [ section_lang ] we introduce the finitary language @xmath0 strongly inspired by abramsky , honda and mccusker s language @xmath14 @xcite , along with its standard game semantics . then we turn to the problem of isomorphisms of types . in section [ section_isomorphisms ] we first give an analysis of isomorphisms in several subcategories of the games model , reproving and extending laurent s theorem , then we use it to characterize isomorphisms in @xmath0 . we show how this characterization fails in the presence of natural numbers , and we give a non - trivial type isomorphism in @xmath14 . @xmath15 & { \simeq}_\mathcal{e } & ( a\to \mathtt{unit})\times ( \mathtt{unit } \to a)\end{aligned}\ ] ]

we investigate the problem of type isomorphisms in a programming language with higher - order references . we first recall the game - theoretic model of higher - order references by abramsky , honda and mccusker . solving an open problem by laurent , we show that two finitely branching arenas are isomorphic if and only if they are geometrically the same , up to renaming of moves ( laurent s forest isomorphism ) . we deduce from this an equational theory characterizing isomorphisms of types in a finitary language with higher order references . we show however that laurent s conjecture does not hold on infinitely branching arenas , yielding a non - trivial type isomorphism in the extension of with natural numbers .

we investigate the problem of type isomorphisms in a programming language with higher - order references . we first recall the game - theoretic model of higher - order references by abramsky , honda and mccusker . solving an open problem by laurent , we show that two finitely branching arenas are isomorphic if and only if they are geometrically the same , up to renaming of moves ( laurent s forest isomorphism ) . we deduce from this an equational theory characterizing isomorphisms of types in a finitary language with higher order references . we show however that laurent s conjecture does not hold on infinitely branching arenas , yielding a non - trivial type isomorphism in the extension of with natural numbers .

1311.0264

i

jets are ubiquitous and are observed to accompany a variety of astrophysical objects such as , stellar - mass and super - massive black hole candidates , neutron stars , white dwarfs , young stellar objects ( ysos ) etc . these outflows exhibit different physical scales and power at one extreme , agns have jets with typical sizes @xmath0 few kpc to few @xmath1 kpc , jet velocities comparable to @xmath2 ( where @xmath2 is the light speed ) , luminosity range @xmath3erg / s and central mass in the range @xmath4 ( where @xmath5 is the mass of sun ) , while in the other extreme , yso jets have typical size @xmath6pc , outflow velocity @xmath7 , luminosity range @xmath8erg / s , and emerge from protostars with mass @xmath9 . in other words , only jets around compact objects are truly relativistic . jets around black hole candidates , be it from agns or micro - quasars , are shrouded in mystery . since black holes do not have hard surface and/or any atmosphere , therefore jets can only originate from the matter accreting onto it . moreover , the terminal speed of jets from around compact objects , though relativistic , but can vary widely too . for jets around grs 1915 + 105 or m87 exhibit terminal speed above ninety percent the speed of light @xcite , while the jet around ss433 is merely around @xmath10 @xcite . therefore , not only there is no consensus about the origin of jets , even the acceleration mechanism of jets are not well understood . there are few interesting properties of jets around compact objects . @xcite showed that the jet around m87 seems to originate within a region less than @xmath11 ( @xmath12 is the schwarzschild radius ) around the central object . in other words , entire accretion disc do not participate in generation of jets , but only the inner region of the accretion disc participate in jet generation . although the connection between jet states and spectral states of the accretion disc has not been conclusively established for massive black hole candidates like the agns , but for micro - quasars , this connection has firmly been established @xcite . persistent , quasi steady , mildly relativistic jets are observed in ` hard spectral state ' ( maximum power in the hard power law tail ) of the accretion disc . the jet seems to get stronger as the spectral state of accretion disc moves to the intermediate states . and truly relativistic jet blobs are generated during state transition to the steep power law state . no jet activity is observed in the canonical soft state ( maximum power in modified black body component ) @xcite . such close corelation of jet with the radiative states of the disc , points to the fact that the accretion disc physics is responsible for jet generation . matter accreting onto a compact object should possess some angular momentum and due to differential rotation some form of anomalous viscosity too . the first viscous disc model seriously considered by the community is the standard thin disc @xcite , although thin disc s inability to explain the origin of power - law photons , as well as , the theoretical inconsistencies like adhoc inner boundary condition , remained an overbearing concern . it was understood that a source of hot electron distribution a comptonizing corona , is required to explain the hard power law photons in the spectra of black hole candidates @xcite . since the boundary condition of black hole accretion is necessarily transonic , disc models with significant advective term gained popularity . the most popular model among the advective disc models was known as adaf or advection dominated accretion flow @xcite . this model is characterized by a single sonic point close to the horizon and subsonic elsewhere . however , it has been shown earlier that multiple sonic point may exist for inviscid rotating flow @xcite , and was confirmed that this is also true for dissipative advective accretion discs @xcite . and therefore it was shown by various authors that adaf is only a subset of general advective solution @xcite . general advective solutions which admits multiple sonic points may harbour standing or time - dependent shock solutions @xcite . shock in accretion has some interesting consequences , for the post shock hot electrons may inverse comptonize soft photons to produce the non - thermal hard radiation tail @xcite . a dominant shock associates with a low supply of soft photons from external keplerian disc , and the hot post - shock region inverse - comptonizes the intercepted photons and produces the low / hard state . and an increased supply of keplerian matter means supply of extra soft photons to cool down the post - shock region which results in weakening of , or , complete removal of the shock to produce the canonical high / soft state . in fact , the hardness intensity diagram ( hid ) of gro j 1655 - 40 was well explained by shocked accretion disc @xcite . these studies also showed that the steady state shock solutions are possible in a limited range of the parameter space , while oscillating or time dependent shocks are possible for a wide range of parameters or boundary conditions @xcite . and since these post - shock region also emits high energy radiations , therefore quasi - periodic oscillation of the shocked disc will give rise to quasi - periodic oscillation in hard radiations as well , and was furthered as a model for quasi - periodic oscillations or qpos @xcite . it was shown from observations that the spectral index increases ( hard to soft transition ) with the increase of qpo frequency , but remarkably the spectral index saturates ( indicating the attainment of high / soft state ) and then there are no qpo detected @xcite . the evolution of the qpo frequency with the spectral state for outburst sources like xtej1550 - 654 , gro 1655 - 40 etc , has been explained well with a model of inward drift of oscillating shock which translates into a spectral state transition from low / hard to intermediate hard . and the final disappearance of qpo with the disappearance of the inner disc or the post - shock disc @xcite . and it has been shown that indeed for the same outer boundary condition , the shock drifts inwards with the increase of the viscosity parameter @xcite . this implies that , with the increase of viscosity the pre - shock disc size increases , which increases the supply of soft photons . as the post - shock disc gets reduced , eventually the total output of the thermal comptonization ( dominant spectra in low / hard state ) decreases too . and since according to the advective accretion disc model , oscillation of post - shock disc gives rise to qpo , so the decrease of shock location increases the qpo frequency , until the shock itself disappears . hence the transition from hard to soft state , or in other words , the increase of spectral index should be correlated with the increase of qpo frequency , and finally the spectral index saturates @xcite as the contribution to the radiation from post - shock disc becomes negligible @xcite . in our previous paper @xcite , we have presented all possible advective viscous accretion solutions , including shocked and shock free solutions . a shocked accretion disc is more interesting , because the post - shock disc being hot can drive bipolar - outflows @xcite . since shock forms typically at @xmath13few @xmath14 , so the assertion that jet base is the inner part of the disc , favours the observational evidence from m87 that jet base is indeed @xmath15 @xcite . since it has also been shown that agns are just a scaled up version of the galactic black holes @xcite , therefore , following the above evidence one may argue that even for galactic black holes the jet base should be close to the central object . however , it is not just theoretical expectation that the inner region around agns and micro - quasars should be similar , therefore , the jet base for microquasars too would be close to the horizon . even in case of galactic black hole candidates ( bhc ) , the detection of strong radio flares ( read jets ) with simultaneous disappearance of qpos and the absence of the comptonized component , points out to the fact that the same region which gave rise to the comptonized component and generated the qpo has been ejected as relativistic jets @xcite . the shocked accretion disc model seems to satisfy all these criteria , starting with the direct evidence of m87 jet originating close to the black hole , the connection between growth of qpo frequency , comptonized component and the radio flare , to the disappearance of jet activity in the soft state ( no or very weak shock ) . @xcite showed ( fig . 5 of their paper ) that the correlation between thermally driven jets from shocked accretion discs and the spectral states from the same discs seems to follow the conclusions of observations of 10 microquasars @xcite . since post - shock disc produces the jets therefore when shock is absent or very weak , jets disappear mimicking the soft state . but thermally driven jets can achieve terminal speed up to @xmath16^{1/2}$ ] , where @xmath17 is the sound speed at the base , which for a shocked disc is the sound speed of the post - shock disc , and @xmath18 is the gravitational potential at the jet base . now the maximum sound speed physically possible is @xmath19 , and that the value of @xmath18 is quite significant because the jet base is rather close to the horizon @xcite . given these facts , the expression of terminal speed given above indicates that , truly relativistic jet terminal speed is not possible by only thermal driving . furthermore , jet states are correlated with the hard spectral states of the accretion disc , therefore , can the disc radiation accelerate the outflowing jet material ? in this respect , one may raise the issue that jet activities are not always observed during the state transition , which might be due to the lack of availability of simultaneous x - ray and radio / infra - red measurements . however , @xcite studied about 10 sources to draw the correlation between jet activity with the hard states , and the conclusion that jets are not seen during the canonical soft states . we would therefore like to study the interaction of radiations from the hard / hard intermediate states with the emanating jet , or in our parlance , the acceleration of jets with the radiation from a shocked disc , and how this radiative acceleration of jets is influenced with the change in viscosity parameter of the disc . it is to be remembered that , since we are investigating the disc in steady state , we are actually studying the generation and acceleration of steady , mildly relativistic jets generally associated with hard to hard intermediate states . the strong radio flares associated with relativistic blob ejections during hard intermediate to soft intermediate state transition @xcite is intrinsically a time dependent phenomenon and has not been addressed in this paper . since we have not incorporated all the physical aspects to mimic the transient phenomena , in this limited sense the results depend on the model assumptions . interaction of the disc radiation with the outflowing matter has been followed by many authors . @xcite studied radiative acceleration of jets above a keplerian disc , but in absence of radiation drag . @xcite showed that radiation drag is important for jets powered by radiation from a thick accretion disc @xcite . including radiation momentum deposition on an axial particle jet illuminated by an infinite thin disc in presence of drag term , @xcite showed that the upper limit of the terminal speed is around @xmath20 of @xmath2 . investigations on radiatively driven jets were extended by @xcite to generate relativistic terminal speeds for particle jets . moreover , the interaction of radiations from shocked accretion disc and jets were studied too @xcite . since shocked discs have two radiation sources , namely , the post - shock and pre - shock disc , therefore the redistribution of radiative power amongst these sources , could efficiently accelerate the jet around its axis . however , jets studied in the above mentioned papers were decoupled from the disc . in this paper we would like to study radiatively driven jet which is generated self consistently from the underlying accretion disc . in other words , we combine the accretion - ejection physics described by @xcite with the effect of radiative momentum deposition on the jets as shown by @xcite . in the next section , we present the simplifying assumptions and equations of motion . in section 3 , we present the methodology of solution . and in the last section we present the solutions and discussion .

very high terminal speed is possible . this mimics the production of steady mildly relativistic but stronger jets as micro - quasars moves from low hard to intermediate hard spectral states . [ firstpage ] hydrodynamics , radiation hydrodynamics , black hole physics , accretion , accretion discs , jets and outflows

we investigate the role of radiative driving of shock ejected bipolar outflows from advective accretion discs in a self consistent manner . radiations from the inner disc affects the subsonic part of the jet while those from the pre - shock disc affects the supersonic part , and there by constitutes a multi stage acceleration process . we show that the radiation from the inner disc not only accelerate but also increase the mass outflow rate , while the radiation from the pre - shock disc only increases the kinetic energy of the flow . with proper proportions of these two radiations , very high terminal speed is possible . we also estimated the post - shock luminosity from the pre - shock radiations , and showed that with the increase of viscosity parameter the disc becomes more luminous , and the resulting jet simultaneously becomes faster . this mimics the production of steady mildly relativistic but stronger jets as micro - quasars moves from low hard to intermediate hard spectral states . [ firstpage ] hydrodynamics , radiation hydrodynamics , black hole physics , accretion , accretion discs , jets and outflows

1311.0264

r

in @xcite we have shown in details various cases of accretion solutions , and also have shown that post shock disc naturally produces bipolar outflows . in this paper , therefore we discuss only the shocked accretion solution . the accretion solutions are characteristic by flow parameters like the grand energy @xmath89 , the specific angular momentum at the horizon @xmath53 ( conversely , @xmath190 at the outer edge of the disc ) and the viscosity parameter @xmath21 . the jet is launched from the disc with the specific energy ( @xmath73 and angular momentum ( @xmath191 ) of the post - shock disc at the jet launch site ( @xmath192 ) . we also compute the moments of radiation fields ( @xmath187 , @xmath188 , @xmath116 ) above the disc , and are used to accelerate the jets . the pre - shock disc radiation depends on @xmath176 , where , @xmath193 is the ratio of the magnetic and the gas pressure and @xmath165 is the accretion rate in units of eddington rate . in order to find the effect of post - shock radiation and pre - shock radiation on jet acceleration , the post - shock luminosity @xmath154 and @xmath176 ( conversely , @xmath152 the pre - shock luminosity ) are supplied as independent parameters . however , since post - shock radiation is produced by inverse - comptonization of self generated and intercepted photons from the pre - shock disc , we compute the post - shock radiation self - consistently by employing the techniques of @xcite . and in figs . ( 8 , 9 , 10 ) the jets are accelerated by self consistent estimation of radiation field , both from pre and post - shock discs . the radiations produced from accretion is governed by the solution . however , we will now treat the post - shock luminosity as a parameter just to see how it affects the jet acceleration . the accretion mach number @xmath194 with @xmath195 is plotted for the parameters @xmath196 , in fig . 3 . we first consider @xmath197 and @xmath198 , the shock is at @xmath199 ( vertical dashed , online black ) , and drives bipolar outflow , where the jet mach number @xmath200 ( dashed , online black ) is plotted with @xmath201 , and the mass outflow rate is @xmath202 and the sonic point of the jet is at @xmath203 . radiation field from the accretion disc deposit its momentum and accelerate the shock generated jets . assuming @xmath204 for same set of accretion boundary condition , accretion - ejection solution is computed . the shock is found to be at @xmath205 ( solid , online blue ) and the jet @xmath200 distribution ( solid , online blue ) has a sonic point at @xmath206 and @xmath207 . the total luminosity for this case is @xmath208 . keeping @xmath176 same , we increase @xmath209 , so the total luminosity increases to @xmath210 , the accretion - ejection solution shows that the mass outflow increases to @xmath211 and the shock in accretion decreases to @xmath212 ( dotted , online red ) . in this case too , due to the increase of radiation , the sonic point decreases to @xmath213 , indicating stronger jet . it is interesting to note that , the pre - shock luminosity increases even though @xmath176 is kept constant , because , with the decrease in @xmath102 , the size of the pre - shock disc increases . [ lab : fig4 ] the jet solutions are explored in more details in the following figure . jet variables @xmath128 ( fig . 4a ) , @xmath214 ( fig . 4b ) , @xmath133 ( fig . 4c ) , @xmath215 ( fig . 4d ) , @xmath73 ( fig . 4e ) and @xmath216 ( fig . 4f ) are plotted with @xmath201 . each curve corresponds to @xmath197 ( dashed , online black ) , @xmath204 ( solid , online blue ) , and @xmath209 ( dotted , online red ) , and which are exactly the same cases of jet solutions as in fig . the increase in @xmath178 , accelerates the jets further , and therefore increases @xmath132 , this in turn decreases the post - shock pressure and the location of the shock front moves close to the horizon . as a result the jet base moves closer . at a given @xmath134 , we find @xmath133 is higher for higher @xmath154 , but difference in @xmath128 or @xmath216 are imperceptible . this shows , that enhanced jet acceleration is due to the radiative momentum deposition onto the jets and not due to conversion of thermal energy to the kinetic one . since higher @xmath154 accelerate the jet , the sonic point is formed closer to the horizon . higher @xmath154 not only means faster jet , but also a jet with higher entropy ( fig . [ lab : fig5 ] the jet terminal speed is defined as @xmath217 where @xmath218 . as shown in figs . 4 , @xmath219 increases appreciably with the increase of @xmath154 and @xmath152 , for a given value of disc viscosity parameter @xmath220 . we would like to see whether this behaviour of @xmath219 holds true for a range of @xmath21 . in fig . 5a , @xmath219 is plotted with @xmath154 , in figs . 5b & 5f , @xmath219 is plotted with @xmath102 and the jet base specific energy @xmath221 . and @xmath132 is plotted with @xmath154 ( fig . 5c ) and @xmath102 ( fig . each curve correspond for @xmath222 ( solid , online red ) , @xmath223 ( dotted , online blue ) , and @xmath224 ( dashed , online black ) . all these figures are generated with outer boundary condition @xmath225 and @xmath226 at @xmath227 . it is clear that @xmath219 increases with @xmath178 at a given value of @xmath21 , as well as , increases with @xmath21 at a given @xmath154 . since @xmath102 moves closer with the increase of both @xmath154 and @xmath21 , the jets are launched with higher @xmath221 , which in turn increases @xmath126 . this is also the reason that the relative mass outflow rate @xmath132 increases with the increase of both @xmath154 and @xmath21 . since @xmath126 increases with @xmath154 and @xmath21 , therefore the jets become supersonic at a distance nearer to the jet base , @xmath82 decreases with the increase of @xmath154 ( fig . 5e ) . [ fig6 ] the effect of radiation from pre - shock disc as it impinges on the jet is illustrated through figs . 6b - f . in fig . 6a , the mach number @xmath23 of the accretion solution is plotted with @xmath195 for disc parameters @xmath228 . the shock is at @xmath205 . we choose @xmath204 , but the pre - shock radiation is changed by varying @xmath176 . the solutions correspond to @xmath229 ( solid , online red ) , @xmath230 ( dotted , online blue ) , and @xmath231 ( dashed , online black ) . the post - shock disc actually hides the base of the jet from most of the radiation from the pre - shock disc , while shines its own light onto the jets ( see fig . [ lab : fig1 ] ) . as a result , if the post - shock radiation remains unaltered and the jet sonic point is formed in the portion of the funnel like region where pre - shock radiation is negligible , then the jet base velocity @xmath126 , the jet base @xmath232 or the jet base properties are likely to remain roughly same , keeping the massloss rate unaltered . consequently , the change in the accretion shock is imperceptible ( fig . all the jet variables closer to the base , @xmath233 ( fig . 6b ) , @xmath234 ( fig . 6c ) , @xmath235 ( fig . 6e ) , and @xmath236 are indistinguishable , while they differ from each other in the supersonic region , where the interaction of pre - shock radiation with the jet is significant too . it is to be remembered , that the temperature plotted here is the single temperature of the outflow . the corresponding electron temperature should be about 2 orders of magnitude less . however , the entropy accretion rates @xmath56 ( fig . 6d ) are distinguishable even at the base . once again it is clear from the temperature plot , that radiative driving is significant . it is also interesting to note from figs . 3 - 4 , that increasing @xmath154 , would result in faster jets , with higher @xmath132 and lower jet sonic point ( @xmath82 ) . while increasing the pre - shock radiation also results in faster jets , but with almost no change in @xmath132 and @xmath82 . since relative mass outflow rates affects the accretion solutions ( eq . [ ef1.eq ] ) , so the feed - back effect of the jet on the disc due to @xmath154 might be more significant than that due to @xmath237 . [ lab : fig7 ] in figs . 7a - d , we investigate how @xmath152 affects the jet solutions for a variety of @xmath21 , but for the same outer boundary condition as in fig . 6 with constant @xmath209 . in fig . 7a , we plot @xmath219 as a function of @xmath238 , where each curve represent disc solutions with @xmath222 ( solid , online red ) , @xmath223 ( dotted , online blue ) , and @xmath224 ( dashed , online black ) . in all these plots @xmath152 varies from @xmath239 . due to radiative driving , @xmath219 increases with @xmath238 , and at a given @xmath238 , it increases with @xmath21 . as has been explained in connection to the previous figure , increasing @xmath21 for a fixed outer boundary decreases @xmath102 , which means the jet base energy @xmath221 increases , resulting in faster jet . however , since the pre - shock disc primarily shines radiation on the supersonic part of the jet , therefore @xmath152 has marginal effect on @xmath82 , and @xmath126 . therefore , @xmath132 is almost constant with the change of @xmath152 ( fig . 7d ) , which in turn keeps @xmath102 almost unchanged ( fig . 7b ) , and the jet sonic point @xmath82 also remains unchanged ( fig . in other words , we may conclude , that the radiation from the inner torus of the accretion disc accelerate the jet , but also increases net mass - loss . on the other hand , radiation from pre - shock disc or the outer disc , accelerates the jet appreciably , although , has almost no effect on @xmath132 . therefore , in the second case we may obtain jets with higher kinetic luminosity . this conclusion is valid for any value of @xmath21 which admits accretion shock . [ lab : fig8 ] having investigated the role the pre - shock and post - shock radiation may have on jets , we actually calculate the @xmath154 from @xmath152 . in appendix a , we have discussed the different radiation processes in a general radiative transfer model ( chakrabarti & mandal 2006 ) . from the accretion disc spectrum , we calculate the ratio of post - shock to pre - shock luminosity ( @xmath240 ) using the viscous transonic solution . we then use a fitting formula of @xmath240 ( eq . [ poly.eq ] ) to calculate the ratio at any given shock location ( @xmath102 ) . in ( fig . [ lab : figa2]1b ) , a typical @xmath177 dependence on @xmath102 is obtained where the dots are the data points from model ( chakrabarti & mandal 2006 ) and solid line represents the fitting function . we assume that the behaviour of this ratio with shock location is generic . the procedure for calculating @xmath241 is as follows for a given set of values of @xmath242 , the accretion solution shows a shock at @xmath102 and a bipolar outflow with some @xmath132 . we then calculate @xmath152 ( eq . [ syn.eq ] ) by supplying @xmath168 and the density and temperature distribution between @xmath173 and @xmath102 . we use the fitting formula of @xmath240 ( eq . [ poly.eq ] ) to calculate @xmath154 . using these the jet solution is obtained . all the solutions presented in figs . ( 3 - 7 ) , we have solved the accretion ejection solution with the following fluid parameters @xmath89 , @xmath53 ( at the horizon , or equivalently , @xmath190 at the outer boundary ) , @xmath21 , and in addition the radiation parameters @xmath154 and @xmath168 ( equivalently @xmath152 ) . now , following the procedures described in appendix a , we reduce one parameter , namely , @xmath154 . in fig . 8a , we plot @xmath102 with @xmath53 , in fig . 8b , we plot the compression ratio @xmath243 with @xmath102 , and in fig . 8c , mass outflow rate @xmath132 with the compression ratio @xmath243 . all the plots are for accretion disc parameters @xmath244 , @xmath245 , and various results has been obtained by varying @xmath53 . the curves are for thermally driven jet ( @xmath246 ; dashed , online red ) , and thermal plus radiatively driven jets ( @xmath247 ; dotted online blue , and @xmath248 ; solid , online black ) . this shows that as the compression at the shock increases , it forces more matter into the jet channel . although @xmath243 increases as @xmath102 decreases , but smaller post - shock region means less matter can be driven as jets , so @xmath132 maximizes at some intermediate @xmath243 . it has also been shown earlier @xcite , that for @xmath111 no shock , @xmath249 for no shock there is no outflow . [ lab : fig9 ] in figs . 9a - l , we have plotted accretion and jet solutions for various @xmath21 and @xmath152 . all the accretion solutions ( @xmath23 with @xmath195 ) are for outer boundary parameters @xmath250 at the outer boundary @xmath227 . the viscosity parameters are @xmath251 ( 9a ) , @xmath252 ( 9d ) , @xmath253 ( 9 g ) , and @xmath254 ( 9j ) . the vertical jumps show the location of accretion shocks , and they are at @xmath255 ( 9a ) , @xmath256 ( 9d ) , @xmath257 ( 9 g ) , and @xmath258 9(j ) . the jet solutions corresponding to these accretion solutions , are presented by @xmath200 ( 9b , 9e , 9h , 9k ) and @xmath133 ( 9c , 9f , 9i , 9l ) . as @xmath21 increases @xmath102 decreases , therefore increasing the pre - shock disc . moreover , with decreasing @xmath102 , the post - shock disc becomes smaller and hotter . so as @xmath102 decreases , initially both @xmath154 & @xmath152 will increase , but at around @xmath259 , further decrease of @xmath102 will reduce @xmath240 and significantly increase @xmath152 ( fig . a1b ) . in figs . 9a , d , g , j , increase of @xmath21 , causes a shift of @xmath260 . consequently , @xmath152 increases from @xmath261 . the resulting jets are accelerated and the terminal velocity increases from @xmath262 as shock shifts from @xmath263 , with the corresponding change in luminosity . by considering the relative proportions of post - shock and pre - shock radiations , decrease of @xmath102 with increasing @xmath21 resembles the disc to move from hard state to hard intermediate state , and simultaneously the jet becomes stronger and faster ( both @xmath219 and @xmath132 increases ) . in fig . 10a - c , we show the comparison of shock parameter space ( @xmath264 ) of the accretion disc without massloss ( dotted , online red ) and with massloss but disc parameter @xmath265 ( long dashed , online black ) and @xmath266 ( dashed , online blue ) , and for various viscosity parameter @xmath267 ( fig . 10a ) , @xmath268 ( fig . 10b ) and @xmath269 ( fig . it is to be noted , that the bounded regions in @xmath264 parameter space , show the parameters for steady state shocks to occur , but non - steady shocks still exist outside the bounded region . the parameter space shrinks when massloss is considered , because with massloss , the post - shock pressure decreases , and the entire range for which steady shock may have existed in absence of jets , will not be able to satisfy the momentum balance across the shock front . moreover , shocks seem to exist for fairly high viscosity and in presence of massloss . [ lab : fig10 ]

radiations from the inner disc affects the subsonic part of the jet while those from the pre - shock disc affects the supersonic part , and there by constitutes a multi stage acceleration process . we show that the radiation from the inner disc not only accelerate but also increase the mass outflow rate , while the radiation from the pre - shock disc only increases the kinetic energy of the flow . with proper proportions of these two radiations ,

we investigate the role of radiative driving of shock ejected bipolar outflows from advective accretion discs in a self consistent manner . radiations from the inner disc affects the subsonic part of the jet while those from the pre - shock disc affects the supersonic part , and there by constitutes a multi stage acceleration process . we show that the radiation from the inner disc not only accelerate but also increase the mass outflow rate , while the radiation from the pre - shock disc only increases the kinetic energy of the flow . with proper proportions of these two radiations , very high terminal speed is possible . we also estimated the post - shock luminosity from the pre - shock radiations , and showed that with the increase of viscosity parameter the disc becomes more luminous , and the resulting jet simultaneously becomes faster . this mimics the production of steady mildly relativistic but stronger jets as micro - quasars moves from low hard to intermediate hard spectral states . [ firstpage ] hydrodynamics , radiation hydrodynamics , black hole physics , accretion , accretion discs , jets and outflows

astro-ph0103432

c

the eight clusters subtended by our slit all have ages below @xmath110 myr , with three having ages @xmath683 myr , for a salpeter imf in the range 1100 m@xmath2 . among the three youngest is cluster 5 , the primary target of our stis observations , whose very young age is in agreement with that inferred by @xcite based on the large observed equivalent width of the h@xmath7 emission line ( ew(h@xmath7)=1650 ) . notably young are clusters 2 and 3 , with ages 8 myr and 3 myr , respectively . for these two clusters , age estimates based on colors give values of @xmath160 myr and @xmath130 myr , respectively @xcite , much larger than what is inferred from uv spectroscopy . age determinations based on colors alone are indeed bound to be relatively uncertain unless additional constraints ( e.g. , h@xmath7 emission ) are available . for instance , consider cluster 2 : the difference in color between a 60 and a 8 myr old instantaneous burst is only @xmath79 mag . the narrowness of this range makes accurate reddening corrections imperative . @xcite deredden their observed colors based on the ratio of h@xmath7 to h@xmath24 ; however the measured equivalent widths are very small ( @xmath80 ) and therefore bound to be uncertain . after correction for galactic foreground reddening and underlying stellar absorption , they find zero magnitudes of foreground attenuation between h@xmath7 and h@xmath24 . by contrast , the reddening derived from our uv spectroscopy is e ( ) = 0.16 , very nearly what is needed to bring the broad - band color age estimate into line . similar results are found for cluster 3 , although the color difference between the two age estimates is greater ( @xmath10.3 ) and can not be entirely reconciled by applying our reddening correction . additional corroboration for the young ages of clusters 2 and 3 comes from an analysis of the soft x - ray emission near the center of ngc 5253 @xcite . the two clusters appear to be located within a superbubble of expanding hot gas . energy limitations constrain the age of the superbubble to be @xmath6410 myr @xcite , in better agreement with the age estimates from uv spectroscopy . the measured and derived properties of the clusters are summarized in tables [ table_cluster_data ] and [ table_cluster_results ] . the ages of the clusters show no particular spatial correlation ( which could indicate propagating star formation . ) their half - light radii span a wide range of values ( 0.6 2.4 pc ) , but visual examination of the profiles suggests that the largest clusters are an unresolved blend of smaller ones . the clusters display varying amounts of reddening , ranging from e ( ) = 0.42 0.05 . the reddening values show a broad spatial correlation ; that is , clusters which are physically close show similar amounts of reddening . the extinction - corrected 1500 luminosities are in the range l@xmath81@xmath82 ergs s@xmath15 @xmath15 for the eight clusters , implying masses in the 10@xmath8310@xmath84 m@xmath2 range , for a low - end imf mass of 1 m@xmath2 . however , both luminosities and masses listed can generally be considered lower limits to the actual values , as discussed in [ clusters ] . we note that the lowest mass clusters ( @xmath85 m@xmath2 or less ) might be subject to strong stochastic effects since only a handful of o - stars are expected to be present for a salpeter imf . these effects could potentially bias our age and mass determinations for clusters 9 , 10 , and 11 . the uv emission from the field regions surrounding the clusters has a clearly stellar origin and is not due to reflected light from the clusters themselves , since , as already mentioned in [ field ] , the spectral features of clusters and field are notably different . in contrast to the clusters spectrum , the field spectrum lacks the strong o - star wind lines of , , and which are signatures of the most massive stars . we stress that this deficiency is not an artifact of undersampling of the field , as our field spectrum contains a considerable amount of light . in fact , the field has a flux nearly equivalent to the integrated cluster spectrum , which contains over @xmath86 m@xmath2 of stars . a similar discrepancy between the cluster and field population has been observed in the starburst galaxy ngc 1569 . using wfpc2 photometry , @xcite find that the stellar population of ngc 1569 is composed of recently formed super star clusters and resolved field stars with ages greater than 10 myr . in order to understand why the field might be deficient in massive stars we have compared the field spectrum of ngc 5253 to three different families of model spectra . the first is an instantaneous burst model with a salpeter imf in the 1100 m@xmath2 range . our best fit model has an age of 8 myr , although this should be considered a lower limit for the reasons discussed in [ field ] . while this model provides a reasonable fit to the data , we rule it out on physical grounds : our field regions are spatially extended ( @xmath87 pc ) and therefore unlikely to be forming stars in an instantaneous burst . the subsequent models we consider have continuous star formation which is probably more appropriate given the galaxy s @xmath37 myr crossing time . since the age of the burst is largely irrelevant in continuous models , we allow the free parameters to be the slope and upper mass cut - off of the imf . our second model uses a fixed salpeter slope and a variable upper mass cut - off . a reasonable fit is produced for an upper mass cut - off of @xmath130 m@xmath2 . the third model fixes the upper mass cut - off at 100 and allows the imf slope to vary . the best fit is achieved by a value of @xmath74 , which is steeper than salpeter , but shallower than the @xmath885 value found by @xcite for the stellar field of the magellanic clouds . an imf slope of @xmath89 is strongly ruled out by the observed blue color of the field s uv continuum ( although it might be argued that our definition of the ` field ' is not as rigorous as massey s . ) we note that our fits are sensitive to stars with masses @xmath420 m@xmath2 which is comparable to the stellar mass range @xmath11560 m@xmath2 sampled by @xcite . the basic result is that the field of ngc 5253 is generally lacking very massive stars , either because of aging or because very massive stars do not form in large numbers . @xcite found that the field accounts for a significant fraction of the uv light from starbursts , between 50% and 80% , and proposed that the field is the outcome of diffuse star formation , a mode different from the one which produces stellar clusters . if the hypothesis that two modes of star formation exist in starbursts is correct , then our observations show that the two modes produce drastically different imfs : a ` regular ' salpeter imf up to @xmath1100 m@xmath2 in clusters , and a massive - star - deficient imf in the field . a scenario other than bi - modal star formation can be suggested to explain the properties of the stellar field . the eight clusters along our stis slit are all younger than @xmath110 myr ; the other three bright clusters in the center of ngc 5253 are younger than @xmath120 myr , although for two of the clusters ages have been derived from photometry alone and can therefore be fairly uncertain @xcite . if the clusters along our slit are representative of the general cluster population in the center of ngc 5253 , we can conclude that the field appears generally older than the clusters or as old as the oldest among them . the field thus contains stars at a more advanced evolutionary stage than the clusters . one way to obtain such a population mix is to hypothesize that stellar clusters dissolve over timescales of @xmath11020 myr and their surviving stars disperse into the field . thus , there is only one star formation mode : stars form in clusters and a fraction of them continue their life in the field . to test this hypothesis , we have constructed a model for the field by subtracting a 10 myr constant star formation population from a 100 myr constant star formation population . star formation has been going on for a while in the center of ngc 5253 ( e.g. , * ? ? ? * ) , and if clusters dissolve over a timescale of @xmath110 myr , the field will consist of stars with ages between @xmath110 myr and the maximum age of the star formation episode , which we take to be 100 myr , although the resulting uv spectrum is largely insensitive to this value . figure [ fieldmodels ] d ) compares the field to the @xmath90 myr model spectrum . the similarity between this model spectrum and the other models shown in figure [ fieldmodels ] is not surprising : the uv spectrum of the @xmath90 myr model is dominated by its youngest , most luminous contributors , i.e. , stars with ages @xmath110 myr which have just come out of dissolving stellar clusters . one prediction of the @xmath90 myr model is that about 40% of the uv light at 1500 is in the field . this fraction becomes slightly higher as one goes to longer wavelengths , for instance , at 2200 ( the wavelength of the @xcite study ) the fraction becomes 45% . however , this value is still somewhat below the 5080% value derived for nearby starbursts @xcite . pushing the dissolution timescale to an age as young as 6 myr , brings the fraction of light in the field to @xmath3450% . however , the differences between the measured and predicted fraction of light in the field may simply reflect the observational difficulty of disentangling small clusters from the field population . star clusters are known to dynamically evolve , with a number of mechanisms contributing to stellar depletion eventual cluster dissolution . however , the dissolution timescales implied by our model for ngc 5253 are very short . we consider the feasibility of these timescales using the model results of @xcite . @xcite calculated the evaporation timescales for compact ( half - mass radius @xmath911 pc ) stellar clusters near the center of the milky way , including stellar evolution among the ingredients . with the possible exception of 5 , our clusters appear fairly compact , with half - light radii @xmath682 pc ; we assume that the half - light radii are a reasonable approximation of the half - mass radii , although mass segregation may have already acted on the oldest clusters to make the first radius smaller than the second . the environment surrounding our clusters is also quite different from that of the milky way . ngc 5253 has about 100 times less baryonic mass than the galaxy , spread over about 20 times less volume ( adopting flattened mass distributions for both galaxies , with similar scale heights ) ; this implies that the central density in ngc 5253 is about 5 times lower than the central density in the milky way . @xcite identify the tidal radius as one of the crucial parameters which determines the evaporation timescale of the stellar clusters ; in ngc 5253 the stellar clusters have tidal radii about 70% bigger than in the milky way , for constant cluster mass , and , thus , evaporation timescales about 2.2 times longer . a 5@xmath010@xmath92 m@xmath2 cluster placed 100 pc away from the dynamical center of ngc 5253 will evaporate in @xmath115 myr for a 1150 m@xmath2 salpeter imf or in @xmath125 myr for a 0.1150 m@xmath2 salpeter imf . we are therefore in the expected ballpark timescale for the less massive among our clusters to agree with the dissolving clusters scenario ; heavier clusters , like 2 , will have lifetimes in the range of 50100 myr and will not contribute significantly to the uv emission of the field . the most massive of our clusters , cluster 5 , has a relaxation time of 400 myr for a 1150 m@xmath2 salpeter imf , and is potentially bound if the imf extends to lower stellar masses . a final consideration is the validity of our definitions of ` cluster ' and ` field ' . the first issue of concern is that some of the less massive objects which we have defined as clusters may simply be random superpositions of a few field o - stars . in this scenario our finding of an massive star deficient field population would be merely circular logic since we would have selectively eliminated many of the o - stars from the field . the brightness of clusters 9 , 10 , and 11 , while lower limits , could be consistent with being one to a few o - stars or b supergiants . however , all of these clusters are well resolved and have relatively smooth spatial profiles . ( cluster 8 , which may include a bright point source , was previously discussed in [ clusters ] . ) an additional check is performed by adding the light from clusters 8 , 9 , 10 , and 11 to our field spectrum . these four clusters contribute about 20% of the total field light , but produce a negligible difference in the integrated spectrum . thus , we can be relatively secure that our choice of clusters is not robbing the field of o - stars . the other issue of concern is the converse : that what we call the field may in fact include a number of faint unresolved clusters . taking the flux of our faintest cluster as our detection limit , we find that a 10@xmath84 m@xmath2 cluster with an e ( ) of 0.2 would be detectable with an age as old as 50 myr , while a 10@xmath92 m@xmath2 cluster with a similar amount of reddening would only be seen at ages less than 15 myr . clusters with masses less than 10@xmath92m@xmath2 probably do not contribute much uv light since they are unlikely to contain many very massive stars due to statistical effects . thus , clusters which are both relatively old and not very massive could contribute somewhat to our field population . however , such light - weight clusters would be subject to a number of destruction mechanisms , and would tend to dissolve on timescales shorter than those discussed above @xcite . most importantly , the addition of faded clusters to the field would not alter the basic notion that there is only one ` mode ' of star formation . the differences seen in the spectra of the field and clusters of ngc 5253 have potentially important implications for restframe uv observations of high redshift galaxies . because of the small angular sizes of high redshift objects , the entire star - forming region is typically observed , with no discrimination between clusters and field . since the field s uv light may represent between 50% and 80% of the uv output from a starburst galaxy @xcite , the common tendency to compare spatially integrated spectra of distant galaxies with the uv spectra of local stellar clusters neglects the important contribution of the field . to quantify this statement , we have created two ` integrated ' spectra , the first combining a 50% ` cluster ' spectrum with 50% ` field ' spectrum , and the second with a 20%80% cluster field mix ( figure [ fiftyfifty ] ) . the ` cluster ' spectrum is the unweighted sum of the eight clusters along our slit prior to dereddening . the 5050 and 20 - 80 template spectra are available for download from http://www.stsci.edu/starburst/templ.html . the spectral features of the 5050 ` integrated ' spectrum closely resemble those of a continuous starburst with a standard salpeter imf extending up to 100 m@xmath2 . the 2080 integrated spectrum has weaker wind lines than the 5050 mix , and may be more appropriate to populations with declining star formation rates . in both cases the stellar wind lines , most notably @xmath771550 , are substantially weaker than in a pure young population . thus , the generally observed weakness or even absence of stellar wind lines in high - z galaxies ( e.g. , * ? ? ? * ) may not be entirely a metallicity effect , but rather a result of time - extended star - forming episodes . the utility of our template spectra for comparisons with high redshift galaxies is illustrated in figure [ cb58 ] , where we compare our 50% cluster50% field spectrum to the spectrum of the gravitationally lensed z = 2.73 starburst galaxy , ms 1512-cb58 @xcite . cb58 appears to be a relatively typical l@xmath93 lyman break galaxy , with z @xmath9 1/3 z@xmath2 @xcite . our empirical template provides an exceptionally good fit overall to the stellar features , particularly to the stellar wind lines . the widths of the interstellar features appear to be fairly well matched , but it must be kept in mind that the interstellar features of the ngc 5253 template spectrum are artificially broadened by blending with intervening milky way absorption features . the intrinsically broader and deeper interstellar features of cb58 are probably a result of the larger covering factor of the gas , and the hydrodynamical consequences of the galaxy s high star formation rate . thanks to the exceptional s / n of both cb58 ( @xmath94 ) and our template spectrum ( @xmath52 ) , figure [ cb58 ] provides one of the best examples to date of the striking similarity between the spectral morphology of a high redshift star - forming galaxy and a local starburst .

we investigate the star formation history of both the bright star clusters and the diffuse ` field star ' population in the dwarf starburst galaxy ngc 5253 using longslit ultraviolet spectroscopy obtained with the space telescope imaging spectrograph ( stis ) . the diffuse light spectrum lacks the strong o - star wind features which are clearly visible in spectra of the brightest clusters .

we investigate the star formation history of both the bright star clusters and the diffuse ` field star ' population in the dwarf starburst galaxy ngc 5253 using longslit ultraviolet spectroscopy obtained with the space telescope imaging spectrograph ( stis ) . the slit covers a physical area of 370.6 pc and includes 8 apparent clusters and several inter - cluster regions of diffuse light which we take to be the field . the diffuse light spectrum lacks the strong o - star wind features which are clearly visible in spectra of the brightest clusters . this discrepancy provides compelling evidence that the diffuse light is not reflected light from nearby clusters , but originates in a uv - bright field star population , and it raises the issue of whether the star formation process may be operating differently in the field than in clusters . we compare our spectra to starburst99 evolutionary synthesis models which incorporate a new low metallicity (/4 z ) atlas of o - star spectra . the clusters are well fit by instantaneous burst models with a salpeter initial mass function ( imf ) extending up to 100 m , and we derive ages for them ranging from 1 to 8 myrs . reasonable fits to the field spectrum are obtained by continuous star formation models with either an upper mass cut - off of m or an imf slope steeper than salpeter ( ) . we favor a scenario which accounts for the paucity of o - stars in the field without requiring the field to have a different imf than the clusters : stellar clusters form continuously and then dissolve on myr timescales and disperse their remaining stars into the field . we consider the probable contribution of an o - star deficient field population to the spatially unresolved spectra of high redshift galaxies .

1408.4750

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the kinematics of the narrow line region ( nlr ) of ngc1068 has been the subject of many studies over the years , the most recent and detailed being those of @xcite and @xcite , based on long - slit optical spectroscopy of the inner few hundred parsecs obtained with the space telescope imaging spectrograph aboard the hubble space telescope ( _ hst - stis _ ) . @xcite have shown that the nlr gas is outflowing in a hollow bi - cone , along which the gas seems to be accelerated up to 140pc from the nucleus and then decelerated . integral field optical spectroscopy of the inner 1.5kpc was obtained by @xcite using the instrument sauron at lower spatial resolution but covering a larger region of the galaxy than in @xcite . @xcite observed the outflow in [ oiii ] @xmath55007 and h@xmath14 , finding also streaming motions towards the nucleus and emission knots of h@xmath14 attributed to regions of star formation in the galaxy plane . @xcite presented optical integral field observations of the inner 400pc using the gemini multi - object spectrograph integral field unit ( gmos - ifu ) at a better spatial resolution ( @xmath1340pc ) which revealed , besides high - velocity gas emission from outflowing gas , also some emission from the gas in the galaxy disc . in the near - infrared ( hereafter near - ir ) , @xcite and @xcite have mapped the gas kinematics via integral field observations using the instrument sinfoni at the very large telescope ( vlt ) . while @xcite focus on the h@xmath11 kinematics in the inner few tens of pc which revealed inflows , @xcite focus on the br@xmath4 and coronal lines kinematics , which are dominated by outflows . in @xcite ( hereafter paper i ) we have used the gemini near - infrared integral field spectrograph ( nifs ) on the gemini north telescope operating with the adaptive optics module altair to map the flux distributions and excitation of the gas within the inner @xmath15pc , while in @xcite we have studied the stellar population . in this paper , we present detailed measurements of the gas kinematics observed in the near - ir emission lines [ feii ] @xmath2 m , h@xmath3 m and br@xmath4 using channel maps and position velocity diagrams . we concluded this is the best way to separate the multiple kinematic components which are present in the emitting gas in this galaxy . the [ feii ] gas kinematics shows a broader " outflow than previously observed in [ oiii ] and in the near - ir coronal lines , being similar to that observed in planetary nebulae and consistent with an origin in an accretion disc wind @xcite or a torus wind @xcite . we test three models with different geometries in order to reproduce the outflow . throughout this paper we adopt a distance of 14.4mpc to ngc1068 which correspond to a scale of 72pcarcsec@xmath8 at the galaxy . this paper is organized as follows . in sec . 2 we present the observations , in sec . 3 we discuss previous studies relevant to the present work , in sec . 4 we present the gas kinematics ( channel maps and _ p - v _ diagrams ) , in sec . 5 we give our interpretation to the kinematics of the [ feii ] , br@xmath4 and h@xmath11 , in sec . 6 we perform the modeling and analysis , in sec . 7 we calculate the mass outflow rate and corresponding power and in sec . 8 we present our conclusions .

we map the kinematics of the inner ( 200pc ) narrow - line region ( nlr ) of the seyfert2 galaxy ngc1068 using the instrument nifs and adaptative optics at the gemini north telescope . channel maps and position - velocity diagrams are presented at a spatial resolution ofpc and spectral resolution in the emission lines [ feii] m , h m and br .

we map the kinematics of the inner ( 200pc ) narrow - line region ( nlr ) of the seyfert2 galaxy ngc1068 using the instrument nifs and adaptative optics at the gemini north telescope . channel maps and position - velocity diagrams are presented at a spatial resolution ofpc and spectral resolution in the emission lines [ feii] m , h m and br . the [ feii ] emission line provides a better coverage of the nlr outflow than the previously used [ oiii] emission line , extending beyond the area of the bi - polar cone observed in br and [ oiii ] . this is mainly due to the contribution of the redshifted channels to the ne of the nucleus , supporting its origin in a partial ionized zone with additional contribution from shocks of the outflowing gas with the galactic disc . we modeled the kinematics and geometry of the [ feii ] emitting gas finding good agreement with the data for outflow models with conical and lemniscate ( or hourglass ) geometry . we calculate a mass outflow rate ofmyr but a power for the outflow of only l . the molecular ( h ) gas kinematics is completely distinct from that of [ feii ] and br , showing radial expansion in an off - centeredpc radius ring in the galaxy plane . the expansion velocity decelerates fromkms in the inner border of the ring to approximately zero at the outer border where our previous studies found a 10 myr stellar population . [ firstpage ] galaxies : individual : ngc1068 galaxies : active galaxies : kinematics and dynamics galaxies : nuclei galaxies : ism ism : jets and outflows

1408.4750

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we have mapped the inner ( 200pc ) nlr kinematics of the seyfert 2 galaxy ngc1068 on the basis of near - ir integral - field spectroscopy in the emission lines [ feii]@xmath2 m , h@xmath3 m and br@xmath4 . we have compared the ionized and molecular gas kinematics and have used three different models to reproduce channel maps and _ p - v _ diagrams of the ionized gas . our main conclusions are : * the br@xmath4 kinematics comprises both blueshifts and redshifts of up to @xmath52kms@xmath8 and its flux distribution in the channel maps is very similar to the flux distribution in [ oiii ] , confirming our conclusion of paper i that the two originate in the same bi - polar outflow . * the [ feii ] kinematics cover the same bi - polar outflow and range of velocities as observed for br@xmath4 , but the flux distributions in the channel maps show a broader ( bowl - shaped hourglass ) bi - polar morphology than the bi - conical shape previously observed in the [ oiii ] flux distribution and also observed in br@xmath4 . this is mainly due to the larger contribution of [ feii ] emission in the redshifted channels . we attribute this result to the origin of the [ feii ] emission in a partially ionized region extending beyond the fully ionized region probed by the br@xmath4 and [ oiii ] emission , with additional contribution from shocks between the nuclear outflow and gas in the galaxy disk . * we conclude that the [ feii ] kinematics provide a better coverage of the nlr outflow thus being a better tracer of the outflow than both [ oiii ] and h@xmath239 emission lines , as it extends to regions not probed by these lines . * the bi - polar bowl shape geometry ( including the partially ionized gas region ) resembles that of many planetary nebulae and that predicted by disc and torus wind models , supporting that such winds are the origin of the observed outflow . * the h@xmath11 kinematics is completely distinct from that of the ionized gas , showing an off - centered ring - like morphology at much lower velocities that suggest expansion in the galaxy plane , at an average velocity of @xmath13100kms@xmath8 as supported by previous co mm observations . * a new result regarding h@xmath11 is our finding of deceleration between the inner and outer border of the ring from @xmath128kms@xmath8 down to zero , which indicates that the expansion is being halted . this result has been predicted in recent hydrodynamic simulations and can be attributed to the interaction of a nuclear jet with the gas in the galaxy disk . this gas is pushed radially away from the nucleus and subsequently halted by the circumnuclear ism . this deceleration reconciles our previous finding of a 10myr stellar population in the ring with its kinematics . * our measurements also suggest that the two h@xmath11 linear structures nt and st ( to the north and south of the nucleus ) which apparently connect the ring to the galaxy nucleus are in outflow ( contrary to the suggested inflows in previous studies ) . * we have built models testing three distinct geometries for the outflow observed in [ feii ] : a conical , a spherical and a lemniscate ( hourglass ) . although the lemniscate model gives a better reproduction of the integrated flux distribution , its kinematics does not provide a significantly better reproduction of the velocity field than the conical model of @xcite ; in both models , the outflow is accelerated to a maximum velocity of 1000kms@xmath8 at 80pc from the nucleus , decelerating to zero in the conical model and keeping its maximum velocity constant in the lemniscate model for distances larger than 80pc from the nucleus . * the calculated mass outflow rate along the nlr is @xmath6m@xmath7yr@xmath8 . similarly to what we and others have found for other seyfert galaxies , this outflow rate is much larger than the mass accretion rate to the agn , indicating that the observed outflow is in fact gas from the inner region of the galaxy pushed by an agn outflow . * the calculated power of the outflow is @xmath240 erg s@xmath8 , which is only @xmath241 , thus smaller than the @xmath242 required to affect significantly the galaxy evolution .

the [ feii ] emission line provides a better coverage of the nlr outflow than the previously used [ oiii] emission line , extending beyond the area of the bi - polar cone observed in br and [ oiii ] . this is mainly due to the contribution of the redshifted channels to the ne of the nucleus , supporting its origin in a partial ionized zone with additional contribution from shocks of the outflowing gas with the galactic disc . we modeled the kinematics and geometry of the [ feii ] emitting gas finding good agreement with the data for outflow models with conical and lemniscate ( or hourglass ) geometry . we calculate a mass outflow rate ofmyr but a power for the outflow of only l .

we map the kinematics of the inner ( 200pc ) narrow - line region ( nlr ) of the seyfert2 galaxy ngc1068 using the instrument nifs and adaptative optics at the gemini north telescope . channel maps and position - velocity diagrams are presented at a spatial resolution ofpc and spectral resolution in the emission lines [ feii] m , h m and br . the [ feii ] emission line provides a better coverage of the nlr outflow than the previously used [ oiii] emission line , extending beyond the area of the bi - polar cone observed in br and [ oiii ] . this is mainly due to the contribution of the redshifted channels to the ne of the nucleus , supporting its origin in a partial ionized zone with additional contribution from shocks of the outflowing gas with the galactic disc . we modeled the kinematics and geometry of the [ feii ] emitting gas finding good agreement with the data for outflow models with conical and lemniscate ( or hourglass ) geometry . we calculate a mass outflow rate ofmyr but a power for the outflow of only l . the molecular ( h ) gas kinematics is completely distinct from that of [ feii ] and br , showing radial expansion in an off - centeredpc radius ring in the galaxy plane . the expansion velocity decelerates fromkms in the inner border of the ring to approximately zero at the outer border where our previous studies found a 10 myr stellar population . [ firstpage ] galaxies : individual : ngc1068 galaxies : active galaxies : kinematics and dynamics galaxies : nuclei galaxies : ism ism : jets and outflows

astro-ph0410640

i

dwarf galaxies are thought to be the building blocks in the assembly of more massive galaxies within the hierarchical picture of structure formation . these galaxies are also very important venues in which questions about cosmology , galaxy evolution , and star formation may be answered . dwarf irregular galaxies are relatively low - mass , gas - rich , metal - poor , and are presently forming stars as shown by their regions , whereas low - mass dwarf spheroidal galaxies are gas - poor and no longer host present - day star - forming events . the properties of these galaxies may be similar to those found in the early universe , and dwarf irregulars may possibly be sites out of which damped lyman-@xmath7 absorber systems form at high redshift ( e.g. , @xcite ) . an important question which has yet to be fully explained is the relationship between dwarf irregular and dwarf spheroidal galaxies ( e.g. , @xcite , and references therein ) . that streams have been observed within the galaxy and m 31 ( e.g. , @xcite ) has been taken as evidence of ongoing accretion and of representing past merging of dwarfs by the more massive galaxies . however , work presented by @xcite and @xcite have shown that stars in present - day dwarf spheroidals can not make up the dominant stellar populations in the halo , bulge , or the thick disk of the galaxy , although the merging of dwarf galaxies at very early times can not be ruled out . the measurements of element abundances provide important clues to understanding the chemical history and evolution of galaxies . in star - forming dwarf galaxies , the analysis of bright nebular emission lines from the spectra of regions is used to derive abundances of @xmath7-elements ( i.e. , oxygen ) in the ionized gas ( see e.g. , @xcite ) . however , a limited number of elements can be studied by comparison to the number of elements found in the absorption spectra of stars . for a more complete picture , additional elements should be included , since various elements arise from different sites and involve different timescales . oxygen and other @xmath7-elements are created in very massive progenitor stars before being returned to the interstellar medium ( ism ) on short timescales , when these stars explode as type ii supernovae . iron is an element produced by explosive nucleosynthesis in type i supernovae from low - mass progenitor stars on longer timescales , and is also produced in type ii supernovae . because of the varying timescales for stars of different masses , the @xmath7 element - to - iron abundance ratio , [ @xmath7/fe ] , = log(x / y ) @xmath8 log(x / y)@xmath9 . ] is tied very strongly with the star formation history ( e.g. , @xcite ) . interestingly , [ @xmath7/fe ] values for three dwarf irregular galaxies are near or at solar , which indicates that stars have been forming at a very low rate and/or the last burst of star formation occurred long ago @xcite . @xcite claim that o / fe is elevated in low metallicity blue compact dwarf galaxies ( [ o / fe ] = @xmath10 ) . however , their analysis does not account for potential depletion of fe onto dust grains , and the fe abundance is only measured in fe@xmath11 , requiring very large and uncertain ionization correction factors ( icfs ) . @xcite finds that the adopted icfs underestimate the total fe abundance by factors larger than the elevated abundance ratio claimed by @xcite . thus , it is prudent to assume that the nebular fe abundances in these galaxies , and thus the nebular o / fe ratios , are quite uncertain @xcite . at present , reliable o / fe ratios will need to be obtained from stellar abundances . while a complete discussion of @xmath7/fe values is beyond the scope of the present work , brief reviews of stellar abundances in external galaxies have recently been presented by @xcite and @xcite . high efficiency spectrographs on 8- and 10-m telescopes have made possible the spectroscopic measurements of individual stars in extragalactic systems . in particular , bright blue supergiants have been observed in galaxies at distances of about 1 mpc . these hot young massive stars allow us to measure simultaneously present - day @xmath7- and iron - group elements . the important advantage of these measurements also allow for the direct comparison of stellar @xmath7-element abundances with nebular measurements , as massive stars and nebulae are similar in age and have similar formation sites . oxygen abundances derived from the spectroscopy of blue supergiants have been obtained in nearby dwarf irregular galaxies ngc 6822 , wlm , and sextans a @xcite . the relative ease with which spectra of regions have been obtained in dwarf irregular galaxies has led to establishing : ( 1 ) the metallicity - luminosity relation , thought to be representative of a mass - metallicity relation for dwarf irregular galaxies ( e.g. , @xcite ) ; and ( 2 ) the metallicity - gas fraction relation , which represents the relative conversion of gas into stars , and may be strongly affected by the galaxies surrounding environment ( e.g. , @xcite ) . it is assumed that nebular oxygen abundances are representative of the present - day ism metallicity for an entire dwarf galaxy , where there is often only a single region present . in fact , spatial inhomogeneities or radial gradients in oxygen abundances have been found to be very small or negligible in nearby dwarf irregular galaxies ( e.g. , @xcite ) , although recent observations have cast uncertainty about the assumption in ngc 6822 and wlm @xcite . here we will focus on oxygen abundances , and the comparison between stellar and nebular determinations . for the remainder of this paper , we adopt 12@xmath0log(o / h ) = 8.66 as the solar value for the oxygen abundance @xcite . wlm ( wolf - lundmark - melotte ) is a dwarf irregular galaxy at a distance of 0.95 mpc @xcite and is located in the local group . the galaxy was discovered by @xcite , and independently rediscovered by lundmark and melotte @xcite . wlm is relatively isolated , as the nearest neighbor about 175 kpc distant is the recently discovered cetus dwarf spheroidal galaxy @xcite . basic properties of the galaxy are listed in table [ table_wlm ] . a number of observations are summarized here . @xcite identified two planetary nebulae in the galaxy , and @xcite identified the brightest blue and red supergiant stars , including over 30 variable stars . ground - based optical photometry of stars were obtained by @xcite , and @xcite . the presence of a single globular cluster was established , and @xcite showed that the properties of the globular cluster are similar to those of galactic globular clusters . in independent imaging programs , @xcite detected two small shell - like features , and @xcite cataloged and measured fluxes for 21 regions in the galaxy . @xcite presented velocity fields for the brightest regions in wlm , and showed that the southern ring is expanding at a speed of 20 km s@xmath12 and that the kinetic age of the bubble is 4.5 myr . recent studies of the resolved stellar populations with the hubble space telescope ( _ hst _ ) have been carried out by @xcite with the wide field planetary camera 2 and by @xcite with the space telescope imaging spectrograph . @xcite found that over half of the stars were formed about 9 gyr ago , and that a recent burst of star formation has mostly occurred in the central bar of the galaxy . @xcite identified the horizontal branch , also confirming the presence of a very old stellar population . in the carbon star survey by @xcite , they found that wlm contained the largest fraction of carbon - to - m stars for the dwarf galaxies surveyed , and showed that wlm is an inclined disk galaxy with no evidence of an extended spherical stellar halo . @xcite searched for molecular gas in wlm , but only upper limits to the co intensity and subsequent h@xmath13 column densities were determined . recent 21-cm measurements with the australia telescope compact array have shown that there are two peaks in the distribution , and that the measured rotation curve is typical for a disk @xcite . the spectroscopy of the brightest regions were reported by @xcite and @xcite . the resulting nebular oxygen abundances were found to be 12@xmath0log(o / h ) @xmath14 , or [ o / h ] @xmath15 . @xcite measured the chemical composition of two a - type supergiant stars in wlm , and showed that the mean stellar magnesium abundance was [ mg / h ] = @xmath5 . however , the oxygen abundance in one of the stars was [ o / h ] = @xmath6 , which is about 0.7 dex or almost five times larger than the nebular abundance . this presents a vexing question : how can the young supergiant be significantly more metal - rich than the surrounding ism from which the star was born ? the research reported here is part of a program to understand the chemical evolution from the youngest stellar populations in the nearest dwarf irregular galaxies ( e.g. , @xcite ) . the motivations are : ( 1 ) to obtain a homogeneous sample of abundance measurements for regions presently known in wlm ; ( 2 ) to measure the temperature - sensitive emission line , derive direct oxygen abundances , and compare the present set of measurements with those in the literature ; and ( 3 ) to examine whether the present measurements show any inhomogeneities in oxygen abundances across the galaxy . this is the first of two papers of our study ; the measurements and analyses for regions in ngc 6822 will be discussed in the next paper ( h. lee et al . , in preparation ) . the outline of this paper is as follows . observations and reductions of the data are presented in sect . [ sec_obs ] . measurements and analyses are discussed in sect . [ sec_analysis ] , and nebular abundances are presented in sect . [ sec_abund ] . our results are discussed in sect . [ sec_discuss ] , and a summary is given in sect . [ sec_concl ] .

this corresponds to [ o / h ] = dex , or 15% of the solar value . in regions where was not measured , oxygen abundances derived with bright - line methods are in general agreement with direct values of the oxygen abundance to an accuracy of about 0.2 dex . in general , the present measurements show that the region oxygen abundances agree with previous values in the literature .

we obtained new optical spectra of 13 regions in wlm with efosc2 ; oxygen abundances are derived for nine regions . the temperature - sensitive emission line was measured in two bright regions hm 7 and hm 9 . the direct oxygen abundances for hm 7 and hm 9 are 12log(o / h ) = and , respectively . we adopt a mean oxygen abundance of 12log(o / h ) = . this corresponds to [ o / h ] = dex , or 15% of the solar value . in regions where was not measured , oxygen abundances derived with bright - line methods are in general agreement with direct values of the oxygen abundance to an accuracy of about 0.2 dex . in general , the present measurements show that the region oxygen abundances agree with previous values in the literature . the nebular oxygen abundances are marginally consistent with the mean stellar magnesium abundance ( [ mg / h ] = ) . however , there is still a 0.62 dex discrepancy in oxygen abundance between the nebular result and the a - type supergiant star wlm 15 ( [ o / h ] = ) . non - zero reddening values derived from balmer line ratios were found in regions near a second peak . there may be a connection between the location of the second peak , regions of higher extinction , and the position of wlm 15 on the eastern side of the galaxy .

astro-ph0410640

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optical spectra of 13 regions were obtained in wlm , and oxygen abundances were derived in nine regions . was measured in bright regions hm 7 and hm 9 . the resulting direct oxygen abundance for hm 7 is in agreement with previously published values . our @xmath89 detection of in hm 9 confirms the lower signal - to - noise measurements reported by @xcite and @xcite . for the remaining regions , oxygen abundances derived with bright - line methods are accurate to about 0.2 dex . we adopt for wlm a mean nebular oxygen abundance 12@xmath0log(o / h ) = @xmath3 , which corresponds to [ o / h ] = @xmath4 , or 15% of the solar value . the upper end of the range of derived nebular oxygen abundances just agrees with the mean stellar magnesium abundance reported by @xcite , but the present mean nebular result is still 0.62 dex lower than the oxygen abundance derived for the a - type supergiant wlm 15 . significant reddening values derived from observed balmer emission - line ratios were found in regions on the eastern side of the galaxy near one of the peaks discovered by @xcite . there may be a relationship between the location of the east peak , regions of redder color ( higher extinction ) , large reddenings derived from balmer emission - line ratios in regions along the eastern side of the galaxy , and the location of wlm 15 . we thank the anonymous referee for comments which improved the presentation of this paper . h. l. thanks dale jackson for a copy of his figures . we are grateful to eso for awarded telescope time , and lisa germany and the staff at eso la silla for their help in acquiring the spectra . h. l. and e. d. s. acknowledge partial support from a nasa ltsarp grant nag 59221 and from the university of minnesota . k. a. v. thanks the national science foundation for support through a career award ast 9984073 . for their one - year visit , e. d. s. and k. a. v. thank the institute of astronomy , university of cambridge for their hospitality and support . this research has made use of nasa s astrophysics data system , and of the nasa / ipac extragalactic database ( ned ) , which is operated by the jet propulsion laboratory , california institute of technology , under contract with the national aeronautics and space administration . garnett , d. r. 2004 , in cosmochemistry : the melting pot of the elements , xiii canary islands winter school of astrophysics , eds . c. esteban , r. j. garca - lpez , a. herrero , & f. snchez ( cambridge : cambridge university press ) , 171 gilmore , g. , & wyse , r. f. g. 1991 , , 367 , l55 krawchuk , c. a. p. , mccall , m. l. , komljenovic , m. , kingsburgh , r. , richer , m. g. , & stevenson , c. 1997 , in iau symp . 180 , planetary nebulae , ed . h. j. habing and h. j. g. l. m. lamers ( dordrecht : kluwer ) , 116 massey , p. , hodge , p. w. , holmes , s. , jacoby , g. , king , n. l. , olsen , k. , smith , c. , & saha , a. 2002 , baas , 34 , 1272 matteucci , f. , 2003 , , 284 , 539 mccall , m. l. , rybski , p. m. , & shields , g. a. 1985 , , 57 , 1 tolstoy , e. , & venn , k. a. 2004 , in highlights of astronomy , vol . 13 , as presented at the xxvth general assembly of the iau , sydney , australia , 1425 august 2003 , ed . o. engvold , ( san francisco : astron . pacific ) , in press ( astro - ph/0402295 ) venn , k. a. , irwin , m. , shetrone , m. d. , tout , c. a. , hill , v. , & tolstoy , e. 2004a , , 128 , 1177 venn , k. a. , tolstoy , e. , kaufer , a. , & kudritzki , r. p. 2004b , in carnegie observatories astrophysics series , vol . 4 : origin and evolution of the elements , ed . a. mcwilliam & m. rauch ( pasadena : carnegie observatories , http://www.ociw.edu/ociw/symposia/series/ + symposium4/proceedings.html ; also astro - ph/0305188 ) wiese , w. l. , fuhr , j. r. , & deters , t. m. 1996 , atomic transition probabilities of carbon , nitrogen , and oxygen : a critical data compilation ( american chemical society for the national institute of standards and technology ) ccc property & value & references + type & ib(s)m & + alternate names & ddo 221 , ugca 444 & + distance & @xmath90 mpc & 1 + linear to angular scale at this distance & 4.6 pc arsec@xmath12 & 2 + @xmath91 & @xmath92 & 3 + @xmath93 & 0.037 & 4 + @xmath94 & @xmath95 jy km s@xmath12 & 5 + @xmath96 & @xmath97 km s@xmath12 & 6 + @xmath98 $ ] & @xmath99 ( @xmath100 0.26 ) & 7 + @xmath101 $ ] , wlm 15@xmath102 & @xmath103 ( @xmath100 0.05 ) & 7 + @xmath104 $ ] , @xmath102 & @xmath105 & 2 + ccc + total area & + field of view & + pixel size & + image scale & + gain & + read - noise ( rms ) & + + length & + width & + & grating # 11 & grating # 7 + groove density & 300 lines mm@xmath12 & 600 lines mm@xmath12 + blaze @xmath42 ( 1st order ) & 4000 & 3800 + dispersion & 2.04 pixel@xmath12 & 0.96 pixel@xmath12 + effective @xmath42 range & 33807520 & 32705240 + lccccccc & date & & & @xmath106 & & & rms + region & ( ut 2003 ) & grating & @xmath107 & ( s ) & @xmath108 & & ( mag ) + ( 1 ) & ( 2 ) & ( 3 ) & ( 4 ) & ( 5 ) & ( 6 ) & ( 7 ) & ( 8) + hm 2 & 28 aug & # 11 & 1 @xmath72 1200 & 1200 & 1.24 & no & 0.034 + hm 2 & 31 aug & # 7 & 3 @xmath72 1200 & 3600 & 1.21 & no & 0.025 + hm 7 & 26 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.06 & yes & 0.030 + hm 8 & 26 aug & # 11 & 7 @xmath72 1200 & 8400 & 1.20 & no & 0.030 + hm 9 & 26 aug & # 11 & 7 @xmath72 1200 & 8400 & 1.20 & yes & 0.030 + hm 9 & 31 aug & # 7 & 3 @xmath72 1200 & 3600 & 1.21 & no & 0.025 + hm 12 & 26 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.06 & no & 0.030 + hm 12 & 28 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.08 & no & 0.034 + hm 16 nw & 27 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.04 & no & 0.029 + hm 16 se & 27 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.04 & no & 0.029 + hm 17 & 28 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.03 & no & 0.034 + hm 18 & 28 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.03 & no & 0.034 + hm 18a & 28 aug & # 11 & 1 @xmath72 1200 & 1200 & 1.06 & no & 0.034 + hm 18b & 28 aug & # 11 & 1 @xmath72 1200 & 1200 & 1.06 & no & 0.034 + hm 19 & 27 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.04 & no & 0.029 + hm 19 & 28 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.08 & no & 0.034 + hm 21 & 28 aug & # 11 & 3 @xmath72 1200 & 3600 & 1.08 & no & 0.034 + rccccccc & & & & + & & & & & & & + @xmath109\;3727 $ ] & @xmath110 & @xmath111 & @xmath112 & @xmath113 & @xmath114 & @xmath115 & @xmath116 + @xmath117 & @xmath118 & & & & & @xmath119 & @xmath120 + @xmath121 & @xmath122 & & & & & @xmath123 & @xmath124 + @xmath125 & @xmath126 & & & & & @xmath127 & @xmath128 + @xmath129\;3869 $ ] & @xmath130 & @xmath131 & @xmath132 & @xmath133 & @xmath134 & @xmath135 & @xmath136 + @xmath137 & @xmath138 & & & & & @xmath139 & @xmath140 + @xmath141 & @xmath142 & @xmath143 & @xmath144 & @xmath145 & @xmath146 & @xmath147 & @xmath148 + @xmath149 & @xmath150 & & & & & @xmath151 & @xmath152 + @xmath153\;4068 $ ] & @xmath154 & & & & & @xmath155 & @xmath155 + @xmath156 & @xmath157 & @xmath158 & @xmath159 & @xmath160 & @xmath161 & @xmath162 & @xmath163 + @xmath164 & @xmath165 & @xmath166 & @xmath167 & @xmath168 & @xmath169 & @xmath170 & @xmath171 + @xmath172\;4363 $ ] & @xmath173 & & & @xmath174 & @xmath175 & @xmath176 & @xmath177 + @xmath178 & @xmath179 & & & & & @xmath180 & @xmath180 + @xmath181 & @xmath182 & & & & & @xmath183 & @xmath184 + @xmath185 + { \rm he\;i}\;4713 $ ] & @xmath186 & & & & & @xmath187 & @xmath187 + @xmath185\;4740 $ ] & @xmath188 & & & & & @xmath189 & @xmath189 + @xmath190 & 0.000 & @xmath191 & @xmath192 & @xmath193 & @xmath194 & @xmath195 & @xmath196 + @xmath172\;4959 $ ] & @xmath197 & @xmath198 & @xmath199 & @xmath200 & @xmath201 & @xmath202 & @xmath203 + @xmath172\;5007 $ ] & @xmath204 & @xmath205 & @xmath206 & @xmath207 & @xmath208 & @xmath209 & @xmath210 + @xmath211 & @xmath212 & & & & & @xmath213 & @xmath214 + @xmath215\;6300 $ ] & @xmath216 & & & & & @xmath217 & @xmath218 + @xmath215\;6363 $ ] & @xmath219 & & & & & @xmath220 & @xmath221 + @xmath222 & @xmath223 & & & @xmath224 & @xmath225 & @xmath226 & @xmath227 + @xmath228\;6583 $ ] & @xmath229 & & & & & @xmath230 & @xmath231 + @xmath232 & @xmath233 & & & & & @xmath234 & @xmath235 + @xmath153\;6716 $ ] & @xmath236 & & & & & @xmath237 & @xmath238 + @xmath153\;6731 $ ] & @xmath239 & & & & & @xmath240 & @xmath241 + @xmath242 & @xmath243 & & & & & @xmath244 & @xmath245 + @xmath246\;7136 $ ] & @xmath247 & & & & & @xmath248 & @xmath249 + @xmath250\;7320 $ ] & @xmath251 & & & & & @xmath252 & @xmath253 + @xmath250\;7330 $ ] & @xmath254 & & & & & @xmath255 & @xmath256 + & & & + & & & + & & & + & & & + & & & + & & & + rccccccc & & & & + & & & & & & & + @xmath109\;3727 $ ] & @xmath110 & @xmath257 & @xmath258 & @xmath259 & @xmath260 & @xmath261 & @xmath262 + @xmath129\;3869 $ ] & @xmath130 & @xmath263 & @xmath264 & @xmath265 & @xmath266 & @xmath267 & @xmath268 + @xmath141 & @xmath142 & @xmath269 & @xmath270 & @xmath271 & @xmath272 & @xmath273 & @xmath274 + @xmath156 & @xmath157 & @xmath275 & @xmath276 & @xmath277 & @xmath278 & @xmath279 & @xmath280 + @xmath164 & @xmath165 & @xmath281 & @xmath282 & @xmath283 & @xmath284 & @xmath285 & @xmath286 + @xmath172\;4363 $ ] & @xmath173 & @xmath287 & @xmath288 & @xmath289 & @xmath290 & & + @xmath190 & 0.000 & @xmath291 & @xmath292 & @xmath291 & @xmath292 & @xmath293 & @xmath294 + @xmath172\;4959 $ ] & @xmath197 & @xmath295 & @xmath296 & @xmath297 & @xmath298 & @xmath299 & @xmath300 + @xmath172\;5007 $ ] & @xmath204 & @xmath301 & @xmath302 & @xmath303 & @xmath304 & @xmath305 & @xmath306 + & & & + & & & + & & & + & & & + & & & + & & & + & & & & + & & & & & & & + @xmath109\;3727 $ ] & @xmath110 & @xmath307 & @xmath308 & @xmath309 & @xmath310 & @xmath311 & @xmath312 + @xmath129\;3869 $ ] & @xmath130 & @xmath313 & @xmath314 & @xmath315 & @xmath316 & @xmath317 & @xmath318 + @xmath137 & @xmath138 & @xmath319 & @xmath320 & @xmath321 & @xmath322 & @xmath323 & @xmath324 + @xmath141 & @xmath142 & @xmath325 & @xmath326 & @xmath327 & @xmath328 & @xmath329 & @xmath330 + @xmath156 & @xmath157 & @xmath331 & @xmath332 & @xmath333 & @xmath334 & @xmath335 & @xmath336 + @xmath164 & @xmath165 & @xmath337 & @xmath338 & @xmath339 & @xmath340 & @xmath341 & @xmath342 + @xmath172\;4363 $ ] & @xmath173 & @xmath343 & @xmath344 & @xmath345 & @xmath346 & @xmath347 & @xmath348 + @xmath181 & @xmath182 & & & @xmath349 & @xmath350 & @xmath351 & @xmath352 + @xmath190 & 0.000 & @xmath353 & @xmath292 & @xmath292 & @xmath195 & @xmath354 & @xmath355 + @xmath172\;4959 $ ] & @xmath197 & @xmath356 & @xmath357 & @xmath358 & @xmath359 & @xmath360 & @xmath361 + @xmath172\;5007 $ ] & @xmath204 & @xmath362 & @xmath363 & @xmath364 & @xmath365 & @xmath366 & @xmath367 + @xmath211 & @xmath212 & @xmath368 & @xmath369 & @xmath370 & @xmath371 & @xmath372 & @xmath373 + @xmath222 & @xmath223 & @xmath374 & @xmath375 & @xmath376 & @xmath377 & @xmath378 & @xmath379 + @xmath228\;6583 $ ] & @xmath229 & @xmath380 & @xmath381 & @xmath382 & @xmath383 & @xmath384 & @xmath385 + @xmath153\;6716,6731 $ ] & @xmath386 & @xmath387 & @xmath388 & @xmath389 & @xmath390 & @xmath391 & @xmath392 + @xmath246\;7136 $ ] & @xmath247 & @xmath393 & @xmath394 & @xmath395 & @xmath396 & @xmath397 & @xmath398 + & & & + & & & + & & & + & & & + & & & + & & & + rccccccc & & & & + & & & & & & & + @xmath109\;3727 $ ] & @xmath110 & @xmath399 & @xmath400 & @xmath401 & @xmath402 & @xmath403 & @xmath404 + @xmath129\;3869 $ ] & @xmath130 & & & & & @xmath405 & @xmath406 + @xmath156 & @xmath157 & & & & & @xmath407 & @xmath408 + @xmath164 & @xmath165 & @xmath409 & @xmath410 & @xmath411 & @xmath412 & @xmath413 & @xmath414 + @xmath190 & 0.000 & @xmath415 & @xmath416 & @xmath417 & @xmath418 & @xmath419 & @xmath420 + @xmath172\;4959 $ ] & @xmath197 & @xmath421 & @xmath422 & @xmath423 & @xmath424 & @xmath425 & @xmath426 + @xmath172\;5007 $ ] & @xmath204 & @xmath427 & @xmath428 & @xmath429 & @xmath430 & @xmath431 & @xmath432 + @xmath211 & @xmath212 & & & & & @xmath433 & @xmath434 + @xmath222 & @xmath223 & @xmath435 & @xmath436 & @xmath437 & @xmath438 & @xmath439 & @xmath440 + @xmath228\;6583 $ ] & @xmath229 & & & @xmath441 & @xmath442 & & + @xmath153\;6716,6731 $ ] & @xmath386 & @xmath443 & @xmath444 & @xmath445 & @xmath446 & @xmath447 & @xmath448 + & & & + & & & + & & & + & & & + & & & + & & & + & & & & + & & & & & & & + @xmath109\;3727 $ ] & @xmath110 & @xmath449 & @xmath450 & @xmath451 & @xmath452 & @xmath453 & @xmath454 + @xmath141 & @xmath142 & @xmath455 & @xmath456 & & & & + @xmath156 & @xmath157 & @xmath457 & @xmath458 & & & & + @xmath164 & @xmath165 & @xmath459 & @xmath460 & @xmath461 & @xmath462 & @xmath463 & @xmath464 + @xmath172\;4363 $ ] & @xmath173 & @xmath465 & @xmath466 & & & & + @xmath190 & 0.000 & @xmath467 & @xmath468 & @xmath469 & @xmath470 & @xmath471 & @xmath472 + @xmath172\;4959 $ ] & @xmath197 & @xmath473 & @xmath474 & @xmath475 & @xmath476 & & + @xmath172\;5007 $ ] & @xmath204 & @xmath477 & @xmath478 & @xmath479 & @xmath480 & @xmath481 & @xmath482 + @xmath211 & @xmath212 & @xmath483 & @xmath484 & & & & + @xmath222 & @xmath223 & @xmath485 & @xmath486 & @xmath487 & @xmath488 & @xmath489 & @xmath490 + @xmath228\;6583 $ ] & @xmath229 & @xmath491 & @xmath492 & & & & + @xmath153\;6716,6731 $ ] & @xmath386 & @xmath493 & @xmath494 & @xmath495 & @xmath496 & @xmath497 & @xmath498 + & & & + & & & + & & & + & & & + & & & + & & & + rccccccc & & & & + & & & & & + @xmath109\;3727 $ ] & @xmath110 & @xmath499 & @xmath500 & & + @xmath190 & 0.000 & @xmath501 & @xmath502 & & + @xmath222 & @xmath223 & @xmath503 & @xmath504 & & + @xmath153\;6716,6731 $ ] & @xmath386 & @xmath505 & @xmath506 & & + & & & + & & & + & & & + & & & + & & & + & & & + & & & & + & & & & & & & + @xmath109\;3727 $ ] & @xmath110 & @xmath507 & @xmath508 & @xmath509 & @xmath510 & @xmath511 & @xmath512 + @xmath129\;3869 $ ] & @xmath130 & & & @xmath513 & @xmath514 & & + @xmath141 & @xmath142 & & & & & @xmath515 & @xmath516 + @xmath156 & @xmath157 & & & @xmath483 & @xmath517 & @xmath518 & @xmath519 + @xmath164 & @xmath165 & @xmath520 & @xmath521 & @xmath522 & @xmath523 & @xmath524 & @xmath525 + @xmath190 & 0.000 & @xmath526 & @xmath527 & @xmath528 & @xmath355 & @xmath355 & @xmath526 + @xmath172\;4959 $ ] & @xmath197 & @xmath529 & @xmath530 & @xmath531 & @xmath532 & @xmath533 & @xmath534 + @xmath172\;5007 $ ] & @xmath204 & @xmath535 & @xmath536 & @xmath537 & @xmath538 & @xmath539 & @xmath540 + @xmath222 & @xmath223 & @xmath541 & @xmath542 & @xmath543 & @xmath544 & @xmath545 & @xmath546 + @xmath228\;6583 $ ] & @xmath229 & & & @xmath547 & @xmath548 & @xmath549 & @xmath550 + @xmath153\;6716,6731 $ ] & @xmath386 & & & @xmath551 & @xmath552 & @xmath553 & @xmath554 + & & & + & & & + & & & + & & & + & & & + & & & + lccccccc property & hm 2 & hm 2 & hm 7 & hm 8 & hm 9 ap1 & hm 9 ap2 & hm 9 ap3 + & ( gr # 7 ) & ( gr # 11 ) & ( gr # 11 ) & ( gr # 11 ) & ( gr # 7 ) & ( gr # 7 ) & ( gr # 7 ) + @xmath58(o@xmath11 ) ( k ) & & @xmath555 & @xmath556 & & @xmath557 & @xmath558 & + @xmath58(o@xmath55 ) ( k ) & & @xmath559 & @xmath560 & & @xmath561 & @xmath562 & + o@xmath55/h @xmath563 & & @xmath564 & @xmath565 & & @xmath566 & @xmath567 & + o@xmath11/h @xmath563 & & @xmath568 & @xmath569 & & @xmath570 & @xmath571 & + o / h @xmath563 & & @xmath572 & @xmath573 & & @xmath574 & @xmath575 & + 12@xmath0log(o / h ) & & @xmath576 & @xmath577 & & @xmath578 & @xmath579 & + 12@xmath0log(o / h ) m91 & 8.17 & 8.11 & 7.84 & 8.01 & 8.03 & 8.06 & 8.15 + 12@xmath0log(o / h ) p00 & 7.92 & 7.85 & 7.67 & 8.18 & 7.92 & 7.99 & 8.23 + ar@xmath11/h @xmath580 & & & @xmath581 & & & & + ar@xmath60/h @xmath580 & & & @xmath582 & & & & + icf(ar ) & & & 1.06 & & & & + ar / h @xmath580 & & & @xmath583 & & & & + log(ar / o ) & & & @xmath584 & & & & + n@xmath55/o@xmath55 & & & @xmath585 & & & & + log(n / o ) & & & @xmath586 & & & & + ne@xmath11/o@xmath11 & & & @xmath587 & & & & + log(ne / o ) & & & @xmath588 & & & & + lcccccc property & hm 9 ap1 & hm 9 ap2 & hm 9 ap3 & hm 12 & hm 12 & hm 16 nw + & ( gr # 11 ) & ( gr # 11 ) & ( gr # 11 ) & ( gr # 11 ) & ( gr # 11 ) & ( gr # 11 ) + @xmath58(o@xmath11 ) ( k ) & @xmath589 & @xmath590 & @xmath591 & & & @xmath592 + @xmath58(o@xmath55 ) ( k ) & @xmath593 & @xmath594 & @xmath595 & & & @xmath596 + o@xmath55/h ( @xmath597 ) & @xmath598 & @xmath599 & @xmath600 & & & @xmath601 + o@xmath11/h ( @xmath597 ) & @xmath602 & @xmath603 & @xmath604 & & & @xmath605 + o / h ( @xmath597 ) & @xmath606 & @xmath607 & @xmath397 & & & @xmath608 + 12@xmath0log(o / h ) & @xmath609 & @xmath610 & @xmath611 & & & @xmath612 + 12@xmath0log(o / h ) m91 & 8.04 & 8.04 & 8.01 & 8.16 & 8.00 & 8.21 + 12@xmath0log(o / h ) p00 & 7.85 & 7.86 & 7.84 & 8.48 & 7.96 & 8.29 + ar@xmath11/h @xmath580 & @xmath613 & @xmath614 & @xmath615 & & & + icf(ar ) & 1.50 & 1.48 & 1.48 & & & + ar / h @xmath580 & @xmath616 & @xmath617 & @xmath618 & & & + log(ar / o ) & @xmath619 & @xmath620 & @xmath621 & & & + n@xmath55/o@xmath55 & & @xmath622 & @xmath623 & & & + log(n / o ) & & @xmath624 & @xmath625 & & & + ne@xmath11/o@xmath11 & @xmath626 & @xmath627 & @xmath628 & & & + log(ne / o ) & @xmath629 & @xmath630 & @xmath631 & & & + + property & hm 17 & hm 19 & hm 19 & hm 21 + & ( gr # 11 ) & ( gr # 11 ) & ( gr # 11 ) & ( gr # 11 ) + 12@xmath0log(o / h ) m91 & 8.17 & 8.24 & 7.64 & 8.14 + 12@xmath0log(o / h ) p00 & & 8.40 & 8.12 & 8.28 + ccccccc & & & + property & hm 2 & hm 9 & hm 7 & hm 9 & hm 7 & hm 9 + o / h ( @xmath597 ) & @xmath632 & @xmath633 & @xmath634 & @xmath345 & @xmath573 & @xmath635 + 12@xmath0log(o / h ) & @xmath636 & @xmath637 & @xmath638 & @xmath639 & @xmath1 & @xmath2 + log(n / o ) & & @xmath640 & @xmath641 & @xmath642 & @xmath586 & @xmath73 + log(ne / o ) & @xmath643 & @xmath644 & @xmath645 & @xmath646 & @xmath588 & @xmath647 + log(ar / o ) & & @xmath648 & @xmath649 & @xmath650 & @xmath584 & @xmath81 +

we obtained new optical spectra of 13 regions in wlm with efosc2 ; oxygen abundances are derived for nine regions . the temperature - sensitive emission line was measured in two bright regions hm 7 and hm 9 . we adopt a mean oxygen abundance of 12log(o / h ) = . however , there is still a 0.62 dex discrepancy in oxygen abundance between the nebular result and the a - type supergiant star wlm 15 ( [ o / h ] = ) . non - zero reddening values derived from balmer line ratios were found in regions near a second peak . there may be a connection between the location of the second peak , regions of higher extinction , and the position of wlm 15 on the eastern side of the galaxy .

we obtained new optical spectra of 13 regions in wlm with efosc2 ; oxygen abundances are derived for nine regions . the temperature - sensitive emission line was measured in two bright regions hm 7 and hm 9 . the direct oxygen abundances for hm 7 and hm 9 are 12log(o / h ) = and , respectively . we adopt a mean oxygen abundance of 12log(o / h ) = . this corresponds to [ o / h ] = dex , or 15% of the solar value . in regions where was not measured , oxygen abundances derived with bright - line methods are in general agreement with direct values of the oxygen abundance to an accuracy of about 0.2 dex . in general , the present measurements show that the region oxygen abundances agree with previous values in the literature . the nebular oxygen abundances are marginally consistent with the mean stellar magnesium abundance ( [ mg / h ] = ) . however , there is still a 0.62 dex discrepancy in oxygen abundance between the nebular result and the a - type supergiant star wlm 15 ( [ o / h ] = ) . non - zero reddening values derived from balmer line ratios were found in regions near a second peak . there may be a connection between the location of the second peak , regions of higher extinction , and the position of wlm 15 on the eastern side of the galaxy .

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recently the growth of rough interfaces has witnessed an explosion of theoretical , numerical , and experimental studies , fueled by the broad interdisciplinary aspects of the subject @xcite . applications can be so diverse as imbibition in porous media , fluid fluid displacement , fire front motion , and the motion of flux lines in superconductors @xcite . in general , a @xmath13-dimensional self - affine interface , described by a single - valued function @xmath14 , evolves in a @xmath15-dimensional medium . usually , some form of disorder @xmath16 affects the motion of the interface leading to its roughening . two main classes of disorder have been discussed in the literature . the first , called thermal or `` annealed , '' depends only on time . the second , referred to as `` quenched , '' is frozen in the medium . early studies focused on _ time - dependent _ disorder as being responsible for the roughening @xcite . here , we consider in detail the effect of _ quenched _ disorder on the growth . the presence of quenched disorder introduces an interesting analogy between the motion of driven interfaces in disordered media and the theory of critical phenomena . the continual motion of the interface requires the application of a driving force @xmath17 . there exists a critical force @xmath18 , such that for @xmath19 , the interface will become pinned by the disorder after some finite time . for @xmath20 , the interface moves indefinitely with an average velocity @xmath21 . this suggests that the motion of driven rough interfaces in disordered media can be studied as a phase transition which we shall call the _ depinning transition_. the velocity of the interface @xmath22 plays the role of the _ order parameter _ , since as @xmath23 , @xmath22 vanishes as @xmath24 we call @xmath25 the _ velocity _ exponent , and @xmath26 the _ reduced force _ ( fig . [ phases ] ) . for @xmath23 , large but finite regions of the interface are pinned by the disorder . at the transition , the characteristic length @xmath27 of these pinned regions diverges as @xmath28 where @xmath29 is the _ correlation length _ exponent . the added phenomenological richness introduced by the quenched disorder leads to an increased difficulty . in fact , the problem of identifying the universality classes for interface roughening in the presence of quenched disorder and determining the corresponding sets of critical exponents has so far remain unsolved . experimental and numerical measurements of some of the critical exponents vary considerably , and the question of the existence of universality classes bas been raised @xcite . the problem is made more complex by the disagreement of most experimentally measured values with analytical calculations @xcite . in this paper , we address the question of why the same exponents vary in value for different systems . we study several numerical models introduced to study interface roughening in the presence of quenched disorder , and identify two universality classes . we show that one of those universality classes can be identified with the case studied analytically . the exponents for the other universality class can not be determined from renormalization groups calculations . however , mappings to directed percolation ( dp ) and isotropic percolation allow us to estimate most scaling exponents . the identification of the universality classes and the calculation of the respective scaling exponents _ at _ the depinning transition enable us to understand the results for most of the models proposed and for some of the experiments . we shall see that several experimental results particularly for the case of the moving interface in fluid - fluid displacement experiments still do not fit the framework provided by the universality classes we discuss . for this reason , we study models in each of the universality classes _ above _ the depinning transition i.e. , in the _ moving _ phase . the results obtained allow us to re - interpret the experimental measurements . furthermore , we find that for one of the universality classes , some of the critical exponents change values at the depinning transition . the paper is organized as follows : in sec . ii we introduce the problem , by describing the set of relevant scaling properties and associated exponents , for driven interfaces moving in disordered media . in sec . iii we discuss the experimental and numerical results motivated our study . in sec . iv we consider several numerical models , and identify two distinct universality classes . in sec . v we try to link the results obtained for the two universality classes with the experimental results . to achieve this goal , we study models , representative of each of the universality classes , above the depinning transition . finally , in sec . vi , we summarize our results and discuss some of the new questions arising from this work .

however , we find that some results can not be understood in terms of the exponents obtained for the two universality classes _ at _ the depinning transition . in order to understand these remaining disagreements , we investigate the scaling properties of models in each of the two universality classes _ above _ the depinning transition . for the dpd universality class , we compare our results with all the relevant experiments . 2

we perform a systematic study of several models that have been proposed for the purpose of understanding the motion of driven interfaces in disordered media . we identify two distinct universality classes : ( i ) one of these , referred to as directed percolation depinning ( dpd ) , can be described by a langevin equation similar to the kardar - parisi - zhang equation , but with quenched disorder . ( ii ) the other , referred to as quenched edwards - wilkinson ( qew ) , can be described by a langevin equation similar to the edwards - wilkinson equation but with quenched disorder . we find that for the dpd universality class the coefficient of the nonlinear term diverges at the depinning transition , while for the qew universality class either or as the depinning transition is approached . the identification of the two universality classes allows us to better understand many of the results previously obtained experimentally and numerically . however , we find that some results can not be understood in terms of the exponents obtained for the two universality classes _ at _ the depinning transition . in order to understand these remaining disagreements , we investigate the scaling properties of models in each of the two universality classes _ above _ the depinning transition . for the dpd universality class , we find for the roughness exponent for the pinned phase , and for the moving phase . for the growth exponent , we find for the pinned phase , and for the moving phase . furthermore , we find an anomalous scaling of the prefactor of the width on the driving force . a new exponent , characterizing the scaling of this prefactor , is shown to relate the values of the roughness exponents on both sides of the depinning transition . for the qew universality class , we find that and are roughly the same for both the pinned and moving phases . moreover , we again find a dependence of the prefactor of the width on the driving force . for this universality class , the exponent is found to relate the different values of the local and global roughness exponent at the depinning transition . these results provide us with a more consistent understanding of the scaling properties of the two universality classes , both at and above the depinning transition . we compare our results with all the relevant experiments . 2

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to summarize , we perform a systematic study of several models proposed to understand the motion of driven interfaces in disordered media . we are able to identify _ two _ distinct universality classes . for one of these universality classes , qew , we observe that it can be described by a langevin equation similar to the ew equation but with quenched disorder . for the qew universality class nearly all exponents for the pinned phase can be obtained by renormalization group calculations . for the other universality class , dpd , we find that it can be described by a langevin equation similar to the kpz equation , but with quenched disorder . furthermore , we find that the coefficient of the nonlinear term @xmath0 diverges at the depinning transition . because of this divergence , no perturbative analytical calculations have been possible so far . however , a mapping of the static properties of the interface , at the depinning transition , to dp yields all static exponents of the problem . a mapping of the dynamics to isotropic percolation yields the dynamical exponent . the identification of these two universality classes leads to some understanding of many of the results obtained previously for models and experiments . however , many other results could not be understood in terms of the exponents obtained for the two universality classes _ at _ the depinning transition . for this reason , we also investigated the scaling properties of the models in the two universality classes _ above _ the depinning transition . we find that for the dpd universality class , @xmath39 and @xmath35 change their values at the depinning transition . furthermore , we find a dependence of the prefactor of the width on the driving force . the new exponent @xmath164 , characterizing the scaling of this prefactor , can be used to relate the values of the roughness exponents on both sides of the transition . for the qew universality class , we find that @xmath39 and @xmath35 remain unchanged at the depinning transition . as for the dpd universality class , we also find a dependence of the prefactor of the width on the driving force . the exponent @xmath164 is , in this case , found to relate the different values of the local , @xmath11 , and global , @xmath215 , roughness exponents at the depinning transition . these results provide us with a more consistent understanding of the scaling properties of the two universality classes both at and above the depinning transition . this knowledge enables us to interpret most of the experimental results obtained previously . however , several questions , that demand an answer , are still unsolved . one of them is the reason for the change in values of the roughness exponent at the depinning transition for the dpd universality class . another is the understanding of the different values of @xmath215 and @xmath11 for the qew universality class . we thank s. v. buldyrev , r. cuerno , s. t. harrington , s. havlin , v. k. horvth , p. ch . ivanov , k. b. lauritsen , h. leschhorn , i. procaccia , p. rey , r. sadr , s. tomassone , t. vicsek , and p .- z . wong for valuable contributions and discussions . l.a.n.a . acknowledges support from junta nacional de investigao cientfica e tecnolgica . the center for polymer studies is supported by the national science foundation .

we perform a systematic study of several models that have been proposed for the purpose of understanding the motion of driven interfaces in disordered media . we identify two distinct universality classes : ( i ) one of these , referred to as directed percolation depinning ( dpd ) , can be described by a langevin equation similar to the kardar - parisi - zhang equation , but with quenched disorder . ( ii ) the other , referred to as quenched edwards - wilkinson ( qew ) , can be described by a langevin equation similar to the edwards - wilkinson equation but with quenched disorder . the identification of the two universality classes allows us to better understand many of the results previously obtained experimentally and numerically . furthermore , we find an anomalous scaling of the prefactor of the width on the driving force . a new exponent , characterizing the scaling of this prefactor , is shown to relate the values of the roughness exponents on both sides of the depinning transition . for the qew universality class , we find that and are roughly the same for both the pinned and moving phases . moreover , we again find a dependence of the prefactor of the width on the driving force . for this universality class , the exponent is found to relate the different values of the local and global roughness exponent at the depinning transition . these results provide us with a more consistent understanding of the scaling properties of the two universality classes , both at and above the depinning transition .

we perform a systematic study of several models that have been proposed for the purpose of understanding the motion of driven interfaces in disordered media . we identify two distinct universality classes : ( i ) one of these , referred to as directed percolation depinning ( dpd ) , can be described by a langevin equation similar to the kardar - parisi - zhang equation , but with quenched disorder . ( ii ) the other , referred to as quenched edwards - wilkinson ( qew ) , can be described by a langevin equation similar to the edwards - wilkinson equation but with quenched disorder . we find that for the dpd universality class the coefficient of the nonlinear term diverges at the depinning transition , while for the qew universality class either or as the depinning transition is approached . the identification of the two universality classes allows us to better understand many of the results previously obtained experimentally and numerically . however , we find that some results can not be understood in terms of the exponents obtained for the two universality classes _ at _ the depinning transition . in order to understand these remaining disagreements , we investigate the scaling properties of models in each of the two universality classes _ above _ the depinning transition . for the dpd universality class , we find for the roughness exponent for the pinned phase , and for the moving phase . for the growth exponent , we find for the pinned phase , and for the moving phase . furthermore , we find an anomalous scaling of the prefactor of the width on the driving force . a new exponent , characterizing the scaling of this prefactor , is shown to relate the values of the roughness exponents on both sides of the depinning transition . for the qew universality class , we find that and are roughly the same for both the pinned and moving phases . moreover , we again find a dependence of the prefactor of the width on the driving force . for this universality class , the exponent is found to relate the different values of the local and global roughness exponent at the depinning transition . these results provide us with a more consistent understanding of the scaling properties of the two universality classes , both at and above the depinning transition . we compare our results with all the relevant experiments . 2

1002.1853

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galaxies consist of vast numbers of stars formed from molecular clouds . it has therefore been suggested that the process of star formation in galaxies depends largely on the distribution , kinematics , and physical conditions of the molecular gas . one of the primary molecular gas properties critical to star formation is the number density . observational studies of molecular clouds in our galaxy suggest that stars are formed from the dense locale of molecular clouds , rather than the diffuse regions ( e.g. , @xcite ) . extragalactic single - dish molecular gas observations indicate that the overall amount of dense molecular gas , which can be traced by the hcn(1 0 ) luminosity , is tightly correlated with the global star formation rate , which can in turn be traced by the far - infrared ( fir ) luminosity observed with the infrared astronomical satellite ( iras ) @xcite . this correlation is much tighter than that between the diffuse molecular gas , or in other words , the total amount of molecular gas that can be traced by @xmath0co(1 0 ) , and the global star formation rate ( e.g. , @xcite ) . in addition , @xcite and @xcite also raise the possibility of the fact that the hcn/@xmath0co luminosity ratio correlates well with the fir/@xmath0co luminosity ratio , namely the fraction of dense molecular gas correlates well with the star formation efficiency , and this suggests that hcn/@xmath0co is a good indicator for star formation . high spatial resolution interferometric observations toward the center of a galaxy with a high infrared luminosity indicate that extragalactic star forming regions coincide well with the distributions of dense molecular gas ( hcn ) @xcite . the distributions of diffuse molecular gas ( @xmath0co ) , on the other hand , only loosely match those of star forming regions . as a matter of fact , the hcn/@xmath0co integrated intensity ratios are high ( @xmath6 ) in active star forming regions in the centers of galaxies with high infrared luminosity ( @xmath7 l@xmath8 ) , but low ( @xmath9 ) in the centers of galaxies with low star forming activities or post - starburst activities @xcite . star forming regions in the outer parts of galaxies , where normally have low infrared luminosities or low star formation rate , have low hcn/@xmath0co at giant molecular cloud scale @xcite . these results strongly imply that the density of molecular gas play a critical role in the active star formation phenomena . the relation between star formation and temperature , another important molecular gas property , has so far not been well established . there are several surveys observing @xmath0co(2 1 ) and @xmath0co(1 0 ) lines toward galaxies with various star formation activities ( such as starburst , interacting , and quiescent galaxies ) , and most of the surveys yield an average @xmath0co(2 1)/(1 0 ) of around unity @xcite . surveys focusing on the @xmath0co(3 2 ) and @xmath0co(1 0 ) lines indicate that variations in @xmath0co(3 2)/(1 0 ) tend to have somewhat larger dependence on star formation activities as compared to @xmath0co(2 1)/(1 0 ) ; starburst galaxies tend to have higher @xmath0co(3 2)/(1 0 ) of around unity , but normal galaxies tend to have lower ratio of around 0.5 or lower @xcite . these multi - transition @xmath0co observations suggest that the @xmath0co lines in nearby normal and starburst galaxies are optically thick , with a tendency to be saturated to unity , namely thermalized , in the vicinity of certain star formation activities . it is therefore difficult to deduce correlations between star formation activities and multi - transition @xmath0co ratios . the intensities of the @xmath1co(1 0 ) lines , on the other hand , display more drastic changes than those of the @xmath0co lines with respect to star formation activities . in merging galaxies , the @xmath1co(1 0 ) intensities tend to be very low , and @xmath0co(1 0)/@xmath1co(1 0 ) often exceed 20 , in contrast to normal or starburst galaxies ( not including extreme starbursts ) that have an average value of @xmath10 @xcite . however , this clear contrast in @xmath0co(1 0)/@xmath1co(1 0 ) is only manifested between merging galaxies and normal / starburst galaxies , and there exists only a weak trend between normal and starburst galaxies as a function of dust temperature or the 60 @xmath11 m and 100 @xmath11 m fir flux ratio @xcite . in the study of m51 multi - line observations , we discovered an excellent density and temperature probe , the hcn(1 0)/@xmath1co(1 0 ) ratio ( @xcite , hereafter paper i ; @xcite ) . the utility of this ratio has been confirmed by higher - j interferometric @xmath0co observations @xcite . in this paper , we present hcn(1 0 ) , @xmath1co(1 0 ) , and @xmath0co(1 0 ) observations toward galaxies with various levels of star formation activities , and discuss the relation between the physical conditions of molecular gas and the levels of star formation activities . in addition , we compare the ir properties of these galaxies , and show that the molecular gas and dust are localized in similar regions and strongly irradiated by the radiation from starburst regions . ( 80mm,80mm)figure1.eps llllcrcc galaxy & type & @xmath12(b1950 ) & @xmath13(b1950 ) & ref . & dist . & ref . & @xmath14 + ngc 253 & sab(s)c & & & 1 & 3.5 & 8 & 10.29 + ngc 2146 & sb(s)ab pec & & & 2 & 17.2 & 9 & 10.93 + ngc 2903 & sab(rs)bc & & & 3 & 8.9 & 10 & 10.05 + m82 & i0 sp & & & 4 & 3.9 & 11 & 10.61 + ngc 3504 & ( r)sab(s)ab & & & 5 & 26.5 & 9 & 10.56 + ngc 6946 & sab(rs)cd & & & 6 & 5.9 & 12 & 10.01 + ngc 6951 & sab(rs)bc & & & 7 & 26.8 & 13 & 10.46 +

in addition , hcn/co in our sample galaxies exhibit strong correlations with the iras flux ratios . it is a well established fact that there exists a strong correlation between dense molecular gas and star formation activities , but our results suggest that molecular gas temperature is also an important parameter .

we performedco(1 0 ) ,co(1 0 ) , and hcn(1 0 ) single - dish observations ( beam size ) toward nearby starburst and non - starburst galaxies using the nobeyama 45 m telescope . theco(1 0 ) and hcn(1 0 ) emissions were detected from all the seven starburst galaxies , with the intensities of both lines being similar ( i.e. , the ratios are around unity ) . on the other hand , for case of the non - starburst galaxies , theco(1 0 ) emission was detected from all three galaxies , while the hcn(1 0 ) emission was weakly or not detected in past observations . this result indicates that the hcn/co intensity ratios are significantly larger ( ) in the starburst galaxy samples than the non - starburst galaxy samples ( ) . the large - velocity - gradient model suggests that the molecular gas in the starburst galaxies have warmer and denser conditions than that in the non - starburst galaxies , and the photon - dominated - region model suggests that the denser molecular gas is irradiated by stronger interstellar radiation field in the starburst galaxies than that in the non - starburst galaxies . in addition , hcn/co in our sample galaxies exhibit strong correlations with the iras flux ratios . it is a well established fact that there exists a strong correlation between dense molecular gas and star formation activities , but our results suggest that molecular gas temperature is also an important parameter .

1002.1853

r

the parameters of the observed lines from all of the sample galaxies ( peak main beam brightness temperature , @xmath40 , and integrated intensity , @xmath41 ) are summarized in table [ table - res - prop ] , and the calculated integrated intensity ratios are summarized in table [ table - res - ratio ] . since we did not observe the @xmath0co(1 0 ) line for the starburst galaxy samples other than m82 and the hcn(1 0 ) line for the non - starburst galaxy samples , we made use instead of the data taken with the nobeyama 45 m telescope from various published papers ( see notes in table [ table - res - ratio ] ) . [ fig - res - m82 ] shows the @xmath0co , @xmath1co , and hcn line spectra toward the observed positions of the central region of m82 , one of the starburst galaxy samples . the overall line shapes of each positions are similar across these three line spectra . the line shapes of all three spectra at the nucleus indicate constant brightness temperatures around the line center , @xmath42 km s@xmath23 . it is also obvious that the @xmath1co line is weaker than other two lines . on the other hand , the line shapes at the off - center indicate peak structures , and the peak brightness temperatures of the ne and sw lobes exceed those of the nucleus in all the observed lines . we did not detect the hcn line in the farthest observed region , ( , ) . the line intensity ratios are , on the other hand , different from the brightness temperature distributions . at the center of m82 , the intensity ratios ( hcn/@xmath1co , @xmath0co/@xmath1co , and hcn/@xmath0co ) are all high , but these ratios gradually decrease with increasing offsets from the center ( table [ table - res - ratio ] ) . fig . [ fig - res - sb ] shows @xmath1co(1 0 ) and hcn(1 0 ) line spectra of the other starburst galaxy samples . both lines have similar line shapes and intensities for all galaxies , which is similar to those for the central @xmath43 region of m82 . we note again that since the hcn and @xmath1co lines were observed simultaneously , there is no hcn/@xmath1co integrated intensity ratio errors due to the relative pointing offsets . lccccccc galaxy & position & @xmath40(@xmath0co ) & @xmath40(@xmath1co ) & @xmath40(hcn ) & @xmath41(@xmath0co ) & @xmath41(@xmath1co ) & @xmath41(hcn ) + ngc 253 & ( , ) & & @xmath44 & @xmath45 & & @xmath46 & @xmath47 + ngc 2146 & ( , ) & & @xmath48 & @xmath49 & & @xmath50 & @xmath51 + ngc 2903 & ( , ) & & @xmath52 & @xmath53 & & @xmath54 & @xmath55 + m82 & ( , ) & @xmath56 & @xmath57 & @xmath58 & @xmath59 & @xmath60 & @xmath61 + ( ne lobe ) & ( , ) & & @xmath62 & @xmath63 & & @xmath64 & @xmath65 + ( sw lobe ) & ( , ) & @xmath66 & @xmath67 & @xmath68 & @xmath69 & @xmath70 & @xmath71 + & ( , ) & @xmath72 & @xmath73 & @xmath74 & @xmath75 & @xmath76 & @xmath77 + & ( , ) & & @xmath78 & @xmath79 & & @xmath80 & @xmath81 + ngc 3504 & ( , ) & & @xmath82 & @xmath83 & & @xmath84 & @xmath85 + ngc 6946 & ( , ) & & @xmath86 & @xmath87 & & @xmath88 & @xmath89 + ngc 6951 & ( , ) & & @xmath90 & @xmath91 & & @xmath92 & @xmath93 + ngc 4736 & ( , ) & @xmath94 & @xmath95 & & @xmath96 & @xmath97 & + ngc 4826 & ( , ) & @xmath98 & @xmath99 & & @xmath100 & @xmath101 & + ngc 5195 & ( , ) & @xmath102 & @xmath103 & & @xmath104 & @xmath105 & + lcccc galaxy & position & hcn/@xmath1co & @xmath0co/@xmath1co & hcn/@xmath0co + ngc 253 & ( , ) & @xmath106 & @xmath107 & @xmath108 + ngc 2146 & ( , ) & @xmath109 & @xmath110 & @xmath111 + ngc 2903 & ( , ) & @xmath112 & @xmath113 & @xmath114 + m82 & ( , ) & @xmath115 & @xmath116 & @xmath117 + ( ne lobe ) & ( , ) & @xmath118 & & + ( sw lobe ) & ( , ) & @xmath119 & @xmath120 & @xmath121 + & ( , ) & @xmath122 & @xmath123 & @xmath124 + & ( , ) & @xmath125 & & + ngc 3504 & ( , ) & @xmath126 & @xmath127 & @xmath128 + ngc 6946 & ( , ) & @xmath129 & @xmath130 & @xmath131 + ngc 6951 & ( , ) & @xmath132 & @xmath133 & @xmath134 + ngc 4736 & ( , ) & @xmath135 & @xmath136 & @xmath137 + ngc 4826 & ( , ) & @xmath138 & @xmath139 & @xmath140 + ngc 5195 & ( , ) & @xmath141 & @xmath142 & @xmath143 + ( 170mm,170mm)figure3.eps fig . [ fig - res - nsb ] shows the @xmath1co(1 0 ) and @xmath0co(1 0 ) line spectra of the non - starburst galaxy samples . the integrated intensity of @xmath0co(1 0 ) line , i(@xmath0co ) , for ngc 4736 is consistent with that of @xcite . for i(@xmath0co ) of ngc 4826 , it is 67% of the value obtained by @xcite . this disagreement may be explained by pointing error and/or calibration error . the pointing error of our observations was @xmath144 , larger than the @xmath145 of @xcite . on the other hand , @xcite did not observe any intensity calibrator as we did with irc@xmath3910216 . for i(@xmath0co ) of ngc 5195 , we only detect 46% of the value obtained by @xcite . this is because we had mistakenly placed the off - position of the position switching observations at ngc 5194 , which is the counterpart of the m51 interaction system for ngc 5195 and rich in molecular gas . this can be seen as the absorption - like feature around the velocity range of @xmath146 km s@xmath23 in fig . [ fig - res - nsb ] , which did not show up in the spectrum of @xcite . therefore we use the derived hcn/@xmath1co value for ngc 5195 as an upper limit . the hcn/@xmath1co integrated intensity ratios between the starburst and non - starburst galaxy samples are significantly different : we obtained an average hcn/@xmath1co toward the nuclei of the starburst samples of @xmath147 , and a value of @xmath148 for starburst samples including the off - center starburst regions of m82 , namely the ne and sw lobes . the average hcn/@xmath1co ratio toward the nuclei of the non - starburst galaxy samples and that including the non - starburst regions of m82 , namely ( , ) and ( , ) , are @xmath4 and @xmath149 , respectively . these values are consistent with previously published results : paper i suggests that starburst regions tend to have higher hcn/@xmath1co of @xmath150 , but less active star forming regions tend to have lower ratios ( @xmath151 ) . note that the results of paper i is based on interferometric observations ; therefore it is sensitive to compact components , such as high density gas ( i.e. , hcn ) . it follows that ratios in paper i are bound to take on larger values than those in this paper , which is based on single - dish observations . the @xmath0co/@xmath1co and hcn/@xmath0co integrated intensity ratios between starburst and non - starburst galaxy samples also show differences with the average values for the starburst samples larger than those for the non - starburst samples : the average @xmath0co/@xmath1co integrated intensity ratios toward the nuclei of the starburst and non - starburst samples are @xmath152 and @xmath153 , respectively , and the average hcn/@xmath0co integrated intensity ratios for these samples are @xmath154 and @xmath155 , respectively . all the hcn/@xmath1co , @xmath0co/@xmath1co , and hcn/@xmath0co ratios for the starburst galaxy samples are @xmath156 times larger than those for the non - starburst galaxy samples . these results suggest that the conditions of molecular gas in the starburst regions differ significantly from those in the non - starburst regions .

emission was detected from all three galaxies , while the hcn(1 0 ) emission was weakly or not detected in past observations . this result indicates that the hcn/co intensity ratios are significantly larger ( ) in the starburst galaxy samples than the non - starburst galaxy samples ( ) .

we performedco(1 0 ) ,co(1 0 ) , and hcn(1 0 ) single - dish observations ( beam size ) toward nearby starburst and non - starburst galaxies using the nobeyama 45 m telescope . theco(1 0 ) and hcn(1 0 ) emissions were detected from all the seven starburst galaxies , with the intensities of both lines being similar ( i.e. , the ratios are around unity ) . on the other hand , for case of the non - starburst galaxies , theco(1 0 ) emission was detected from all three galaxies , while the hcn(1 0 ) emission was weakly or not detected in past observations . this result indicates that the hcn/co intensity ratios are significantly larger ( ) in the starburst galaxy samples than the non - starburst galaxy samples ( ) . the large - velocity - gradient model suggests that the molecular gas in the starburst galaxies have warmer and denser conditions than that in the non - starburst galaxies , and the photon - dominated - region model suggests that the denser molecular gas is irradiated by stronger interstellar radiation field in the starburst galaxies than that in the non - starburst galaxies . in addition , hcn/co in our sample galaxies exhibit strong correlations with the iras flux ratios . it is a well established fact that there exists a strong correlation between dense molecular gas and star formation activities , but our results suggest that molecular gas temperature is also an important parameter .

1002.1853

c

we conducted a survey of @xmath0co(1 0 ) , @xmath1co(1 0 ) , and hcn(1 0 ) lines toward seven starburst and three non - starburst galaxies nearby using the nobeyema 45 m telescope ( beam size @xmath2 ) . the @xmath1co(1 0 ) and hcn(1 0 ) lines were obtained for all the sample galaxies , but the @xmath0co(1 0 ) data for starburst galaxy samples and the hcn data for non - starburst galaxy samples were obtained from previously published data . * the @xmath1co(1 0 ) and hcn(1 0 ) intensities in the central regions of the starburst galaxy samples are more or less similar , with the hcn/@xmath1co integrated intensity ratios ranging between 0.75 1.61 ( average @xmath292 ) . the @xmath1co(1 0 ) intensities in the non - starburst galaxy samples are always stronger than the hcn(1 0 ) intensities , and hcn/@xmath1co yield obviously smaller values of @xmath4 than for the starburst galaxy samples . we observed multiple positions for the starburst galaxy m82 , and the ratios far from the center ( i.e. , disk region ) are similar to those in the non - starburst galaxy samples . * @xmath0co/@xmath1co and hcn/@xmath0co also show higher values for about a factor of two in starburst galaxy samples than those in the non - starburst galaxy sample . * the physical attributes of molecular gas derived from the line ratios under the lvg model indicate dense ( @xmath206 @xmath165 ) and warm ( @xmath293 k ) conditions in most of the central regions of the starburst galaxy samples , but diffuse ( @xmath294 @xmath165 ) and cold ( @xmath201 k ) conditions in the non - starburst galaxy samples . under the pdr model , this suggests that the dense molecular gas ( @xmath295 @xmath165 ) is being irradiated by isrf of @xmath282 g@xmath280 in the starburst galaxy samples , but lower density molecular gas of @xmath296 @xmath165 is being irradiated by lower intensity isrf of @xmath284 g@xmath280 in the non - starburst galaxy samples . * hcn/@xmath1co exhibits tight correlations with the iras flux ratios between @xmath5 and other wave bands , namely , the increase of hcn/@xmath1co is related to the increase of the iras @xmath5 flux . since the iras @xmath5 flux is a good tracer for star formation activities , these correlations indicate that hcn/@xmath1co is also a good tracer for star formation activities . high hcn/@xmath1co larger than unity points to dense and warm molecular gas with the temperature of 100 k or more under the lvg model , or irradiated by strong isrf under the pdr model . the high @xmath5 flux also indicates high isrf and high dust temperature of around 100 k or more . these results suggest that molecular gas and dust are localized in the same regions in a well mixed configuration , and that the strong radiation heats up the dust and therefore the molecular gas nearby indirectly . this strong radiation also affects the molecular gas itself . we are grateful to the nro staff for the operation and improvement of the nobeyama 45 m telescope . this work is supported by the national science council ( nsc ) of taiwan , nsc 96 - 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we performedco(1 0 ) ,co(1 0 ) , and hcn(1 0 ) single - dish observations ( beam size ) toward nearby starburst and non - starburst galaxies using the nobeyama 45 m telescope . theco(1 0 ) and hcn(1 0 ) emissions were detected from all the seven starburst galaxies , with the intensities of both lines being similar ( i.e. , the ratios are around unity ) . on the other hand , for case of the non - starburst galaxies , theco(1 0 ) the large - velocity - gradient model suggests that the molecular gas in the starburst galaxies have warmer and denser conditions than that in the non - starburst galaxies , and the photon - dominated - region model suggests that the denser molecular gas is irradiated by stronger interstellar radiation field in the starburst galaxies than that in the non - starburst galaxies .

we performedco(1 0 ) ,co(1 0 ) , and hcn(1 0 ) single - dish observations ( beam size ) toward nearby starburst and non - starburst galaxies using the nobeyama 45 m telescope . theco(1 0 ) and hcn(1 0 ) emissions were detected from all the seven starburst galaxies , with the intensities of both lines being similar ( i.e. , the ratios are around unity ) . on the other hand , for case of the non - starburst galaxies , theco(1 0 ) emission was detected from all three galaxies , while the hcn(1 0 ) emission was weakly or not detected in past observations . this result indicates that the hcn/co intensity ratios are significantly larger ( ) in the starburst galaxy samples than the non - starburst galaxy samples ( ) . the large - velocity - gradient model suggests that the molecular gas in the starburst galaxies have warmer and denser conditions than that in the non - starburst galaxies , and the photon - dominated - region model suggests that the denser molecular gas is irradiated by stronger interstellar radiation field in the starburst galaxies than that in the non - starburst galaxies . in addition , hcn/co in our sample galaxies exhibit strong correlations with the iras flux ratios . it is a well established fact that there exists a strong correlation between dense molecular gas and star formation activities , but our results suggest that molecular gas temperature is also an important parameter .

1405.3239

c

_ chandra _ observations of 21 show spectral softening over the pwn , with the photon spectral index ranging from @xmath164 at the inner ( radius @xmath165 ) region to @xmath166 at the outer @xmath167 radius annulus . _ nustar _ observations confirm this by showing spectral softening below @xmath168 kev , as shown in table [ tab : specfit ] . the broad _ nustar _ psf causes some mixing of the spectra in different annuli , and as a result the variation of @xmath169 with radius obtained by _ _ is less pronounced than that seen by _ chandra_. _ _ finds a spectral break at @xmath170 kev in the integrated pwn emission . the spectral break is also observed in the inner regions with radius @xmath171 and in an annulus from @xmath167 . the break is statistically significant at radii @xmath172 . above @xmath44 kev the photon spectral index remains constant . there are several possible origins for the spectral break seen by _ nustar_. one possibility is that the _ nustar _ psf mixes the radially dependent power - law indices seen by _ chandra _ @xcite , and softens the spectrum in such a way as to cause a sharp break . however , simulations that fold _ chandra _ maps through the _ nustar _ response indicate that this is not the case . the effects of the large ism extinction @xcite again would not cause such a sharp , defined energy break . similarly , the loss effect of dust scattering at lower energies is negligible ( below @xmath173)in the _ nustar _ band because of the relatively low column absorption . contributions from the pulsar are also not likely to be responsible . most pulsars have a harder spectrum than the pwn they power . while this could in fact cause a sharp transition between photon indices , it would cause spectral hardening with energy , not the softening seen by _ nustar_. finally , spectral breaks are often attributed to synchrotron cooling , as proposed by @xcite . however , the break energy of 9 kev would require an unreasonably low magnetic field strength of @xmath174 @xmath175 , compared to the @xmath176 @xmath177 g derived from equipartition arguments @xcite . the prominent spectral steepening between radio and x - rays , if interpreted with simple cooling models , yields magnetic field strengths ranging from @xmath178 @xcite to @xmath179 @xcite . it is likely that the spectral break results from physical effects , either due to a break in the injected electron energy spectrum or due to energy losses due to particle transport in the pwn . pulsars emit pairs of relativistic electrons and positrons , which are accelerated at a termination shock near the pulsar itself . downstream of the termination shock the accelerated electrons interact with the magnetic field , also produced by the pulsar , and subsequently emit synchrotron radiation from the radio through gamma energy bands . the injection spectrum can therefore shape and influence the spectrum of the synchrotron radiation , as noted by @xcite . these authors propagate a broken power - law electron spectrum through a time - dependent model that includes energy losses due to synchrotron radiation , inverse compton scattering , and adiabatic cooling . _ provides confirmation that the relatively simple injection spectrum used in @xcite is not adequate to fit the observed x - ray data , as seen in figure [ fig : sed ] . the model , noted as the solid black line , has a steep negative slope in the x - ray band and does not fit the x - ray spectra obtained from _ chandra _ , _ xmm - newton _ , _ integral_/ibis , and now _ nustar_. it is therefore reasonable to explore whether a more complex model can explain the 9 kev spectral break . @xcite extend the models with the addition of diffusive losses as well as a broken injection spectrum with a discontinuity at the break energy . however , both the aforementioned sed models do not include the spatial dependence of parameters such as the magnetic field of the pwn , which provides additional complexity and can perhaps better fit the x - ray data . we explore these effects in the following sections . particle transport in pwne has long been a matter of discussion and study . unfortunately , few celestial objects are both bright enough and large enough to allow distinguishing radially - dependant features to fit to the various existing models . the crab nebula , 21 and 3c 58 are such pwne . they have been frequently observed and analyzed , and have provided valuable insights into the physics of magnetohydrodynamic ( mhd ) flows and relativistic shocks that govern the appearance of pwne ( e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) . extending the energy range of analysis will allow for more detailed probing of radially - dependant physics . this information is important both to understand pwne and to isolate the properties of the relativistic shock at the pwn inner edge from the subsequent spectral evolution downstream . we shall ask : can the observable parameters of 21 from radio to x - ray be reproduced assuming the shock injects only a single structureless power - law particle spectrum ? one such parameter used as a spectral fingerprint of various models is the radial dependency of the power - law photon index . numerous observations have confirmed softening of the 21 pwn spectrum with increasing projected radius @xcite . this is shown at higher energies for the _ nustar _ observations in figure [ fig : rve ] . the softening is associated with synchrotron cooling of the electrons , and the corresponding decrease in the maximum emitted x - ray energy in the bulk velocity flow downstream of the termination shock . an alternative approach is to characterize the variation of source size with photon energy using a characterization of the ` cooling length ' @xmath125 , such as the source fwhm . since only the energy - dependence of this length is important for modeling the spectral steepening , its precise definition is not important . this scale depends only on mapping the total number of photons as a function of radius and energy to determine the scale length @xmath125 . this is more straightforward than spectral modeling because counting statistics are almost always limited , and length scale measurements do not require determining a spectrum at each radius . we therefore use the cooling length scale , with fwhm as its surrogate , as the fundamental diagnostic for extracting information about physical conditions . we shall also make use of the observed steepening from radio to x - rays of 21 through the parameter @xmath180 . most discussions of pwn physics ( e.g. * ? ? ? * ) simply take this as an intrinsic property , but we shall attempt to explain it through evolutionary effects . there exist two prominent mechanisms that have been invoked to explain pwne particle transport : advection and diffusion . beginning with @xcite and @xcite , diffusion has long been investigated as a cause for the characteristics of a pwn . however , the early models of particles propagating outwards from a central source purely by diffusion , applied exclusively to the crab nebula , have been unable to account for the detailed x - ray properties of the crab , such as its change of size with frequency @xcite . pure advection models have also been proposed , such as @xcite . the canonical theory involving pure advection as the method of particle transport was presented by ( * ? ? ? * hereafter kc84 ) . when kc84 was used to predict the radial behavior of the spectrum , the resultant spectral photon index has little to no variation from the center of the nebula outwards , and begins to vary only towards the pwn periphery ( * ? ? ? * hereafter tc12 , figure 2 ) . this also does not match the observed behavior of a slowly - steepening x - ray spectrum @xcite . tc12 provide a nuanced approach to particle transport by diffusion and present two updated models . they claim that the magnetic field is not predominately toroidal far from the termination shock , as is often assumed in pwn theory , but has a more complex geometry with cross - field transport best described by diffusion . their first model consequently incorporates pure diffusion only , with both the magnetic field and diffusion coefficient constant with radius , and synchrotron emission as the only loss of energy . tc12 argue that such a model better explains the radial dependence of @xmath169 as seen in the crab , 3c58 , and 21 , with proper adjustment of the diffusion coefficient . involving complexities such as an energy - dependent diffusion coefficient might be more physically reasonable , but the data are not sufficiently constraining to distinguish these cases from a simple diffusion model . while the pure diffusion model of tc12 appears to describe observations of the crab and 3c 58 relatively well , we argue that it is less appropriate for 21 . it does provide a good description of @xmath181 for the crab and 3c 58 ( @xmath182 ) , however the fit of this model to the 21 @xmath183 kev data is poor ( @xmath184 ) , as seen in figure 6 in tc12 . in addition , the ratio of advective to diffusive timescales that determines what process dominates is radially dependant . using @xmath185 downstream of the pwn termination shock ( kc84 ) , and the know relationships @xmath186 and @xmath187 , we obtain @xmath188 . 21 is very compact , with a size more than two times smaller than that of the other two pwne , and thus advection is likely to dominate . finally , the advective model provides a good fit to the energy dependent cooling length scale ( see below ) . tc12 presented the radially - dependant spectral index @xmath181 rather than using the cooling length scale @xmath125 as characteristic of their model , which makes fitting the model to higher energy _ data too difficult . the second model presented by tc12 involves a monte carlo simulation that includes both diffusion and advection transport close to and farther away from the pulsar , respectively . this allows a more complex treatment than previous analytical models @xcite . while likely a more appropriate approach for 21 , tc12 only applied this simulation to the crab and 3c 58 . kc84 provide a complete advective solution for a steady , spherically symmetric wind terminated by a magnetohydrodynamic ( mhd ) shock . although kc84 is routinely applied to determine quantities such as the mean downstream magnetic field , its range of applicability is in fact more narrow . kc84 represents an idealized theory , suited to the case of constant injection of electrons in a spherical geometry , transported outward by pure advection in an ideal mhd flow with an ordered , toroidal magnetic field . the model does not attempt to reproduce the crab spectrum from radio to x - rays , but only the optical to x - ray portion , with an injection spectral index of optically emitting electrons of @xmath189 . the predicted value of steepening of @xmath190 of 0.51 is roughly appropriate ( so their cooling break is at uv wavelengths ) . this value is fortuitously close to the value of 0.5 for a stationary , homogeneous source . thus this model also can not reproduce radio - to - x - ray seds of many other pwne , including 21 , which have a larger @xmath191 . as mentioned above , the @xmath181 relationship predicted by the kc84 model is flatter in the pwn interior and softens towards the edges , as shown by @xcite , while generally a gradual variation in @xmath181 is observed . this has motivated several generalizations of kc84 . the values we obtain from the _ nustar _ data for @xmath125 and @xmath192 are clearly inconsistent with the model presented in kc84 . the gradients implied by the assumptions of kc84 , predict @xmath193 , independent of spectral index , and @xmath194 for the physically important inner flow region . if we attempt to apply the kc84 formalism to describe the radio - to - x - ray spectrum of g21.5 - 0.9 with @xmath195 and @xmath196 , we fail on both counts . first , we find @xmath4 ( @xmath197 ) . second , we find the observed spectral indices in the radio and x - ray bands produce @xmath198 , instead of 5/9 from a kc model using the injected spectral index of @xmath199 . * hereafter r09 ) noted that there are a number of physical effects not accounted for in kc84 that could produce a steeper spectral break than @xmath200 . for example , the magnetic field may have a significant radial or turbulent component , or it may not satisfy mass conservation due to cloud evaporation , or it may not have magnetic flux conservation ( e.g. due to magnetic reconnection or turbulent amplification ) . r09 constructed a simple model that includes these effects . the model involves generating simple scaling relations for the downstream magnetic field @xmath201 , fluid velocity field @xmath202 , and fluid density @xmath203 in terms of the dimensionless length scale @xmath204 where @xmath205 is the inner injection radius . the non - spherical geometrical effects could also be parameterized in terms of jet width @xmath206 where @xmath207 corresponds to a conical jet or a section of spherical outflow ; a confined jet has @xmath208 , while a flaring jet would have @xmath209 . by assuming @xmath201 , @xmath202 and @xmath203 all vary as power - laws in @xmath210 with indices @xmath211 , @xmath212 and @xmath213 , r09 obtains a series of general consistency relations that these indices must satisfy with each other and with observable parameters . these variables of @xmath214 , @xmath215 and @xmath191 , the energy scaling of the cooling length , particle injection index and spectral index break , respectively , provide constraints on the allowed values of @xmath216 , @xmath217 , @xmath218 , and @xmath219 . the results of r09 can be rewritten in terms of the functional form of @xmath214 , and assuming @xmath220 as observed for g21.5 - 0.9 : @xmath221 independent of @xmath218 . since we observe @xmath222 and @xmath223 , this gives @xmath224 . the possible solutions are thus very restrictive for our measured value of @xmath191 and @xmath214 . additionally , if the flow conserves mass ( disallowing , for instance , mass loading by evaporation of thermal material ) , then the density index @xmath219 is linked to the velocity index @xmath218 . in this case , some solutions are unphysical , such as those with @xmath225 , corresponding to an accelerating downstream fluid . with some judicious rejection of such solutions we can draw some interesting general conclusions , based on the possible values of the observables , which may guide further investigations . for a conical or spherical flow , @xmath226 , so either density or magnetic - field strength , or both , must _ rise _ with radius ( since either @xmath219 or @xmath217 is positive , or both ) . mass conservation links @xmath219 to @xmath218 , but if that assumption is abandoned , there is no relation and no constraint on the velocity profile only the density profile matters for observable quantities . a steeply decelerating flow can produce @xmath227 with mass conservation , but mass loading can also do this . similarly , @xmath228 can be a reasonable outcome of flux non - conservation through processes such as reconnection . our observations require one or both of these effects : addition of mass to the flow through some kind of evaporation , and increase in magnetic - field strength beyond flux freezing . a strongly confined jet ( @xmath208 ) can relax some constraints ; for @xmath229 , we only require @xmath230 . however , even here either mass or flux nonconservation is necessary . one can construct constant density solutions ( @xmath231 ) but such a geometry is disfavored due to the high symmetry of 21 as evidenced in both the broad axial symmetry observed in the radio @xcite and in the soft x - ray band @xcite . while @xcite expands on the treatment of kc84 , both fail to reproduce the steadily steepening spectrum with radius shown by g21.50.9 and other pwne . this shortcoming is characteristic of models in which particles are transported outwardly purely by advection , so that all particles at a given radius have similar ages . to produce steady spectral steepening probably requires a mixture of particles of different ages at each radius . this could be caused by more complex fluid flow such as the back flows found in simulations by @xcite , or by particle diffusion . we conclude that a model describing both the radio - to - x - ray spectrum of 21 and the size shrinkage with x - ray energy we observe can be accommodated in a pure advection model requiring the injection of only a straight power - law spectrum of electrons , @xmath232 . however , as with all pure advection models , the gradual rather than sudden steepening of the spectrum with radius is not reproduced . the viability of this explanation for the observed properties of 21 will depend on whether the addition of diffusion can reproduce the gradual steepening while preserving the successes of the advection model . _ nustar _ has detected , for the first time , the north spur and eastern limb above 10 kev . three main theories have been proposed to explain the nature of these features : they are extensions of the pwn itself , they are limb - brightened shock fronts propagating into surrounding ism and accelerating cosmic rays , or they result from an interaction of ejecta with the envelope of the progenitor snr , presumably a type iip supernova @xcite . since the north spur and eastern limb have different spectral and spatial properties , we discuss them separately . a multi - wavelength analysis is required to get a full understanding of the north spur . this feature was observed in the radio and the soft x - ray , most recently by @xcite and @xcite , respectively . @xcite reported a radio detection of the north spur , with a 1.43 ghz flux density of @xmath233 mjy , and a fwhm size of @xmath234 . this is notable because it is the only feature , other than the pwn itself that is detected in the radio band . the eastern limb has no radio emission detected to date . @xcite obtained @xmath235 ks of _ chandra _ data , and found that the north spur has a spectrum comprised of non - thermal and thermal components . the thermal component , represented by the * pshock * model , is best - fit to temperature of @xmath236 kev and contributes only @xmath237 to the overall @xmath238 kev flux . the non - thermal component , however , is equally well - fit by either the * srcut * or * powerlaw * model . the model * srcut * describes the synchrotron emission from a homogeneous source consisting of a power - law energy distribution of electrons with an exponential cutoff , radiating in a uniform magnetic field . the emitted spectrum is a power - law that steepens slowly above the photon energy corresponding to the electron cutoff energy . this slow curvature can mimic a steeper power - law in a limited energy band . however , in a broader energy band the * srcut * model can fall well below the extrapolation of a power - law with the same slope at lower energies . since x - ray emission is visible from the north spur at energies as high as @xmath132 kev , the correct spectral model must provide a photon flux from @xmath130 kev that is statistically higher than the background . due to signal - to - noise limitations we can not use _ nustar _ data to spectrally fit the spur , however we can use the deconvolved images to distinguish between the * srcut * and * powerlaw * models . we simulated spectra with these models using the _ fakeit _ command in xspec using the model parameters reported by @xcite . a photon spectral index of @xmath239 was applied to the * powerlaw * model , while the * srcut * model used a radio index of @xmath240 and a rolloff frequency of @xmath241 hz . the _ nustar _ response files were based on a point source extraction with @xmath242 . we were thus able to obtain fluxes from each respective model from @xmath129 kev , @xmath130 kev , and from @xmath135 kev . both models have count rates higher than that of the background within the @xmath129 kev energy band . in the @xmath130 kev band , the * powerlaw * model has a count rate 7 times higher than the background , while the * srcut * model is only 3 times higher . finally , within the @xmath130 kev band , the count rates are 4 and 1.5 higher than the background for the * powerlaw * and * srcut * models , respectively . this implies that the * srcut * model should be marginally visible up to @xmath132 kev , and above @xmath132 kev should have a count rate equal to that of the background . this matches well with what is seen in the _ nustar _ images . the * powerlaw * model , however , should be detectable at energies as high as @xmath243 kev . if the north spur were an extension of the pwn , it would have a spectral photon index similar to that of the pwn itself . while this is true , the analysis above indicates that the north spur is not described by a * powerlaw * model extending to higher energies . if it were , the north spur would easily be detectable at energies as high as @xmath243 kev . however , the _ nustar _ images with a combined exposure of 281 ksec do not detect any statistical emission above @xmath132 kev , indicating that * srcut * is the more plausible spectral model for the north spur . it is possible that the north spur results from the interaction of the inner sn ejecta with the h - envelope of the progenitor @xcite . this is supported by the thermal component in the spectral fit of @xcite , a * pshock * model with solar abundances , low temperature of @xmath244 kev , and low ionization timescales . this is also supported by the morphology of the north spur itself . with the inclusion of projection effects , the north spur is located between @xmath245 and the edge of the sn shell at @xmath246 . x - ray emission from the shell of 21 is clearly visible in the _ nustar _ image . our results confirm the existence of this shell , revealed by _ chandra _ @xcite in both their image and in an extracted shell spectrum ( up to @xmath174 kev ) , but also hinted at in earlier _ xmm - newton _ data @xcite . the _ xmm - newton _ observations reveal evidence of the shell in a @xmath247 kev energy band image , after careful subtraction of a modeled dust scattering component below @xmath248 kev . the _ nustar _ detection extends up to much a higher energy of @xmath1 kev . the morphology of the _ nustar _ emission is striking in its similarity to the _ chandra _ and especially the _ xmm - newton _ image . emission is detected from pa @xmath249 to @xmath250 in the @xmath128 kev image ( pa = 0 at n , positive clockwise ) , with the extent shrinking as the energy increases until it is visible mainly in the east and north at the highest energies . this is consistent with the intensity distribution with position angle seen in the lower energy image . a question unresolved by previous x - ray observations is whether the shell emission is thermal or non - thermal . the extended energy response of _ nustar _ can be exploited to answer this question . @xcite found that the spectrum of the eastern limb could be characterized equally by four distinct models . a thermal fit to the * pshock * model provided a temperature of @xmath251 kev while a non - thermal * powerlaw * model obtained a spectral photon index of @xmath252 . two * srcut * models were also well - fit to the eastern limb spectrum . ideally * srcut * requires both a radio flux density and radio spectral index for the shell , but the eastern limb has not been detected in the radio . therefore , two values of the radio index @xmath215 that are reasonable for a sn shell were chosen ( @xmath253 ) while all other parameters were left free to vary . care was taken to ensure the best - fit radio flux was below the upper limit reported by @xcite . as with the north spur , we extrapolated the four _ chandra _ spectra for the eastern limb into the _ nustar _ band . we created an effective area file for an extended source shaped like the eastern limb , then used the _ fakeit _ command in xspec to simulate spectral data . the thermal * pshock * model predicted a shell flux which would not produce the x - ray emission seen by _ nustar _ at @xmath254 kev . in contrast , the three non - thermal models produced x - ray fluxes consistent with imaging of the eastern limb by _ nustar _ , although the * srcut * and * powerlaw * models could not be distinguished from each other . nonetheless , the _ nustar _ observations firmly establish the non - thermal nature of the shell x - ray emission . the detection of a non - thermal shell up to quite high x - ray energy in 21 is interesting , and is in contrast to observations of other crab - like supernova remnants . recently shells have been detected in 3c58 @xcite and g54.1 + 0.3 @xcite , and a clear , detached shell of emission in kes 75 @xcite . however the 3c58 shell is clearly thermal , with no sign of a non - thermal component . the shell of @xmath255 can be fit with both thermal and non - thermal models , however a thermally emitting shell seems much more likely . assuming thermal emission , @xcite were able to use pwn - snr evolutionary models to obtain an age consistent with the characteristic age derived from pulsar observations , obtain the proper supernova - pwn radius ratio , and predict that the reverse shock has not encountered the pwn yet , consistent with other observations . the ages of 3c58 and g54.1 + 0.3 are @xmath256 years and @xmath257 years , respectively . 21 is thus unique in that it is much younger ( @xmath258 years ) , and potentially has higher forward shock speed , both of which could lead to the detectable non - thermal shell . the crab nebula itself , of comparable age to 21 but much closer , still shows no non - thermal shell , presumably due to a very low interstellar medium density . the detection of this 21 non - thermal shell at quite high x - ray energy is thus likely due to its younger age compared to these other crab - like snrs .

we present _ nustar _ high energy x - ray observations of the pulsar wind nebula ( pwn)/supernova remnant 21 . we detect integrated emission from the nebula up to kev , and resolve individual spatial features over a broad x - ray band for the first time . the morphology seen by _ nustar clearly detects non - thermal emission up to kev that extends along the eastern and northern rim of the supernova shell . the broadband images clearly demonstrate that x - ray emission from the north spur and eastern limb results predominantly from non - thermal processes . we detect a break in the spatially integrated x - ray spectrum at kev that can not be reproduced by current sed models , implying either a more complex electron injection spectrum or an additional process such as diffusion compared to what has been considered in previous work . we find this to be inconsistent with the model for the morphological evolution with energy described by . this value , along with the observed steepening in power - law index between radio and x - ray , can be quantitatively explained as an energy - loss spectral break in the simple scaling model of , assuming particle advection dominates over diffusion .

we present _ nustar _ high energy x - ray observations of the pulsar wind nebula ( pwn)/supernova remnant 21 . we detect integrated emission from the nebula up to kev , and resolve individual spatial features over a broad x - ray band for the first time . the morphology seen by _ nustar _ agrees well with that seen by _ xmm - newton _ and _ chandra _ below 10 kev . at high energies _ nustar _ clearly detects non - thermal emission up to kev that extends along the eastern and northern rim of the supernova shell . the broadband images clearly demonstrate that x - ray emission from the north spur and eastern limb results predominantly from non - thermal processes . we detect a break in the spatially integrated x - ray spectrum at kev that can not be reproduced by current sed models , implying either a more complex electron injection spectrum or an additional process such as diffusion compared to what has been considered in previous work . we use spatially resolved maps to derive an energy - dependent cooling length scale , with . we find this to be inconsistent with the model for the morphological evolution with energy described by . this value , along with the observed steepening in power - law index between radio and x - ray , can be quantitatively explained as an energy - loss spectral break in the simple scaling model of , assuming particle advection dominates over diffusion . this interpretation requires a substantial departure from spherical magnetohydrodynamic ( mhd ) , magnetic - flux - conserving outflow , most plausibly in the form of turbulent magnetic - field amplification .

1009.2761

i

one of the main ongoing efforts in cold atom gases is the investigation of strongly correlated phases . our theoretical understanding of strongly correlated phases is , in general , far from complete . for example , computational studies , of fermions in particular , are severely limited . as a result , the possibility of performing analog simulations of model hamiltonians , using cold atoms in optical lattices@xcite , has raised great hopes . the remarkable controllability of cold atom systems , allowing , for example , the application of a specific time - dependent perturbation , has also opened the possibility of studying strongly correlated systems in regimes inaccessible to solid state materials , especially away from equilibrium . among all model hamiltonians relevant to the physics of strong correlations , the hubbard model has attracted the greatest attention . on one hand , this model is the simplest to have important competition between kinetic and potential energies . it also plays in the field of strong correlations a somewhat analogous role to the one played by the ising model in classical statistical mechanics . on the other hand , its physics is of direct relevance to high - temperature superconductivity , a phenomenon still veiled in mystery . in fact , this new field often dubbed ` condensed matter of light and atoms ' was pioneered by the theoretical prediction@xcite and experimental observation of an incompressible regime , characteristic of a mott insulator , and of the transition between this phase and itinerant ones , first for bosons@xcite and recently also for fermions@xcite . for recent reviews , see , e.g. , refs . . in order to make progress towards the ultimate goal of performing analog simulations of model hamiltonians , a good synergy between experimental efforts and theoretical investigations is crucial . for example , theoretical inputs are useful in establishing maps , in parameter space , of the location of the different phases present in a realistic setup which takes into account the trap confining potential . moreover , experiments are currently confronted with the great difficulty of cooling fermions in optical lattices to sufficiently low temperatures to reach many interesting strongly correlated phases . this relevant temperature range is significantly lower than the one corresponding to mere quantum degeneracy . theoretical control over these issues is greatly needed and requires a quantitative understanding of the thermodynamic properties of the hubbard model , both for the homogeneous system and in the presence of a trap . in this article , we perform a comprehensive study of the thermodynamic properties of the homogeneous three - dimensional fermionic hubbard model , and of cold fermionic atoms in a three - dimensional optical lattice subjected to a trapping potential . we focus on the range of temperature which is of direct interest for current experiments as well as for the next generation of experiments . particular emphasis is put on aspects related to cooling of the system . the main theoretical technique used in the present study is dynamical mean - field theory ( dmft ) . this approach ( reviewed , e.g. , in ref . ) is a controlled approximation which is able to capture the competition between the kinetic energy , that tends to delocalize atoms over the whole lattice , and the repulsive potential energy that prevents atoms from occupying the same site , hence promoting localization . we also use another theoretical approach , namely high order high - temperature series expansions@xcite . one of the goals of the present article is to delimit , in parameter space , the respective range of validity of each of these approaches , and to provide a benchmark for their use through quantitative comparisons . this article is organized as follows . in sec . [ sec : model_methods ] , we define the model considered in this article , specify notations and conventions and briefly outline the theoretical methods used . in sec . [ sec : hom ] , we provide detailed results for the thermodynamics of the homogeneous hubbard model in three dimensions . finally , the effect of the trapping potential is considered in sec . [ sec : trap ] , with several applications geared towards cooling fermionic cold atom systems .

we present a comprehensive study of the thermodynamic properties of the three - dimensional fermionic hubbard model , with application to cold fermionic atoms subject to an optical lattice and a trapping potential . special attention is devoted to understand the implications that thermodynamic properties of this system have on cooling .

we present a comprehensive study of the thermodynamic properties of the three - dimensional fermionic hubbard model , with application to cold fermionic atoms subject to an optical lattice and a trapping potential . our study is focused on the temperature range of current experimental interest . we employ two theoretical methods - dynamical mean - field theory and high - temperature series - and perform comparative benchmarks to delimit their respective range of validity . special attention is devoted to understand the implications that thermodynamic properties of this system have on cooling . considering the distribution function of local occupancies in the inhomogeneous lattice , we show that , under adiabatic evolution , the variation of any observable ( e.g. , temperature ) can be conveniently disentangled into two distinct contributions . the first contribution is due to the redistribution of atoms in the trap during the evolution , while the second one comes from the intrinsic change of the observable . finally , we provide a simplified picture of a recently proposed cooling procedure , based on spatial entropy separation , by applying this method to an idealized model .

1009.2761

c

in this article , we performed a detailed study of the thermodynamics of the three - dimensional fermionic hubbard model , for a rather wide range of couplings . we mainly focused on the temperature regime @xmath216 , of current interest for experiments on cold fermionic atoms in optical lattices . our theoretical study is mainly based on single - site dynamical mean - field theory ( dmft ) , a well established theoretical method based on a controlled approximation in which non - local correlations are neglected but local quantum fluctuations are treated accurately . in addition , we used high - temperature series expansion . a comparative study between these two methods allowed for a precise assessment of their respective range of validity . dmft is found to be accurate down to fairly low temperatures when not too close to half - filling ( one particle per site ) . because of their convergence properties , the series expansion are most useful at low density or exactly at half - filling . at or close to half - filling , single - site dmft can be trusted only down to @xmath217 . below this temperature , short - range magnetic correlations set in , which require the use of cluster extensions of dmft . hence , our study validates the use of single - site dmft for understanding experimental results on cold fermionic atoms in a 3d lattice in the currently accessible temperature range , while future experiments at lower temperature will require extensions of the method . we considered the implications of the thermodynamic properties of the homogeneous system for fermionic atoms in an optical lattice confined in a parabolic potential , within the local density approximation . a state diagram was established , with different regimes for the density profile in the trap . special emphasis was devoted to the distribution function of site occupancies in the trap , a quantity which can be experimentally measured by imaging techniques with single lattice - site resolution . such techniques have recently become available for two - dimensional systems . this distribution function proved to be of particular use when discussing how a given observable ( e.g. , temperature ) changes in the trap as the system evolves in an adiabatic manner when a parameter is varied . indeed , it allows for a clear separation of two contributions , one corresponding to the redistribution of atoms in the trap during the evolution , and another from the intrinsic change of the observable . we applied these considerations to the temperature change in the trap under an adiabatic variation of the coupling , and identified the regimes where a significant cooling can be expected . however , we would like to point out that for these results to be completely applicable to trapped cold atoms confined to optical lattices , one would need to take into account several processes that could prevent a fully adiabatic evolution . considering the effects of processes such as lattice heating will be the subject of future works . finally , we elaborated on a previously proposed cooling mechanism , based on the separation of regions of small and large entropy . this procedure is promising for cooling further cold fermionic systems by approximately one order of magnitude , a necessary step and major future challenge for accessing and studying experimentally strongly correlated phases in those systems . _ note added : _ when the present work was near completion we became aware that another study , conducted by fuchs _ et al . _ , on the thermodynamics of the 3d hubbard model was also in its final stage . the focus of ref . is on the characterization of the low temperature region near the antiferromagnetic transition . in the temperature range where our two works overlap , the results are in agreement . we are grateful to m. ferrero and o. parcollet for discussions and for sharing with us their ct - qmc code . we thank s. wessel for providing us with the entropy data of the heisenberg model from ref . . we acknowledge discussions and previous collaborations on related subjects with i. bloch , t. esslinger , f. gerbier , e. gull , r. jrdens , m. khl , j. oitmaa , l. pollet , a. rosch , c. salomon , and m. troyer . we acknowledge funding from the agence nationale de la recherche , the darpa - ole program , the ` triangle de la physique ' and the fonds qubcois de recherche sur la nature et les technologies .

our study is focused on the temperature range of current experimental interest . we employ two theoretical methods - dynamical mean - field theory and high - temperature series - and perform comparative benchmarks to delimit their respective range of validity . the first contribution is due to the redistribution of atoms in the trap during the evolution , while the second one comes from the intrinsic change of the observable . finally , we provide a simplified picture of a recently proposed cooling procedure , based on spatial entropy separation , by applying this method to an idealized model .

we present a comprehensive study of the thermodynamic properties of the three - dimensional fermionic hubbard model , with application to cold fermionic atoms subject to an optical lattice and a trapping potential . our study is focused on the temperature range of current experimental interest . we employ two theoretical methods - dynamical mean - field theory and high - temperature series - and perform comparative benchmarks to delimit their respective range of validity . special attention is devoted to understand the implications that thermodynamic properties of this system have on cooling . considering the distribution function of local occupancies in the inhomogeneous lattice , we show that , under adiabatic evolution , the variation of any observable ( e.g. , temperature ) can be conveniently disentangled into two distinct contributions . the first contribution is due to the redistribution of atoms in the trap during the evolution , while the second one comes from the intrinsic change of the observable . finally , we provide a simplified picture of a recently proposed cooling procedure , based on spatial entropy separation , by applying this method to an idealized model .

0804.1906

c

the radio galaxy 4c+24.36 has wat morphology in all the images presented in this paper ( figs . [ fig : hr_image610 ] and [ fig : hr_images ] ) , with two bright continuous jets and very extended radio lobes . such components are very symmetric in total flux density and extent ( tab . 2 ) , as well as in spectral index properties and physical parameters ( tabs . 5 and 6 ) . these results suggest that the major axis of 4c+24.36 most probably lies close to the plane of the sky . + we searched for further hints of the source orientation in the plane of the sky by means of a standard analysis based on the jet asymmetry . assuming that the jets are intrinsically symmetric with respect to the source core , the jet to counterjet brightness ratio @xmath80 can be used to constrain the geometry and velocity of the jets in the context of a relativistic beaming model ( e.g. lind & blandford 1985 ) according to @xmath81 where @xmath82 is the ratio of the jet velocity to the speed of light , @xmath83 is the orientation angle of the jet with respect to the line of sight , and @xmath37 is the jet spectral index . if the jet emissivity is isotropic with no preferred direction for the magnetic field ( pearson & zensus 1987 ) , the exponent @xmath84 is given by @xmath85 . using the 0.7@xmath86 resolution image at 4.9 ghz ( see insert in fig . [ fig : cartoon ] ) , and assuming the jet east to be the counterjet , we estimated @xmath80 within the inner @xmath87 kpc from the core . assuming @xmath88 for the jet emission , we found @xmath89 which yields @xmath90=0.05 ( eq . [ eq : ratio ] ) . [ fig : beta ] shows the corresponding constraints on @xmath83 and the intrinsic jet velocity @xmath82 ( solid black curve ) . jetha , hardcastle & sakelliou ( 2006 ) found that the average value for the inner jet speed in a relatively large sample of wat radio galaxies is @xmath91 . this velocity is in general agreement with the values found for fri radio galaxies , whose properties are consistent with the hypothesis that jets slow down from relativistic to sub relativistic velocities on scales of 110 kpc ( parma et al . 1994 ) . adopting @xmath91 for 4c+24.36 , the black solid curve in fig . [ fig : beta ] shows that the allowed jet orientation angle is in the range @xmath92 @xmath93 ( red dashed region ) . this suggests that the source probably lies at a very small angle with respect to the plane of the sky . + if we use the exponent @xmath94 in eq . [ eq : ratio ] , which is valid in the case of a perfectly ordered magnetic field parallel to the jet axis ( begelman 1993 ) , we obtain very similar constraints for the jet orientation , as shown by the solid blue curve in fig . [ fig : beta ] . in this case @xmath95@xmath96 . the radio structure of 4c+24.36 is characterised by clear distortions occurring over different linear scales . one of most prominent features is the number of sharp wiggles which the jets undergo within the central @xmath97 kpc ( projected ) from the core ( fig . [ fig : profile ] ) . on the large scale , the overall structure of the source appears slightly bent toward the north in a c shape which is typical of wat sources ( fig . [ fig : hr_image610 ] and fig . [ fig : hr_images ] ) . this suggests that different physical processes may play a role in the origin of the morphological distortions observed on the different scales . jet oscillations have been observed in other fri radio sources of similar luminosity as 4c+24.36 , e.g. the well studied radio galaxies 3c31 ( e.g. , blandford & icke 1978 ; andernach et al . 1992 ; laing & bridle 2002 ) and 3c449 ( e.g. , andernach et al . 1992 ; feretti et al . 1999 ) . both sources are characterized by a very large total extent ( lls @xmath1 800 kpc and 600 kpc , respectively ) which places them among the class of giant radio galaxies . they are associated with the dominant members of two nearby poor groups of galaxies ( z=0.17 ) , and both galaxies are likely undergoing a gravitational encounter with a close bright companion . in fig . [ fig : morph ] we compare the radio morphology of 4c+24.36 ( upper panel ) to the structure of the well - known radiogalaxies 3c31 and 3c449 ( central and lower panels , respectively ) . all images were obtained from a new reduction of 1.4 ghz observations from the vla public archive , and have a resolution of @xmath98 ( see figure caption for details ) . note that the images of 3c31 and 3c449 have been rotated and reversed in order to highlight the morphological similarities . we also point out that the image of 3c449 shows only the central region of the source , whose total extent at this resolution is @xmath99 ( i.e. @xmath1 420 kpc ; see feretti et al . 1999 ) . despite the different linear size , the similarity of the pattern of wiggles in the three sources is striking . however we can notice some important differences : _ i ) _ the wiggles in 4c+24.36 occur over a smaller projected distance from the nucleus ( i.e. between @xmath17 kpc and @xmath125 kpc ; see fig . [ fig : profile ] ) than in 3c31 and 3c449 , where the first bend is observed at @xmath100 kpc ; _ ii ) _ the inner jets in 4c+24.36 show a much stronger deviation from linearity than 3c31 and 3c449 . in particular , the western jet appears already bent at @xmath13 kpc only from the core ( see insert in fig . [ fig : cartoon ] ) . + + jet oscillations can be ascribed to various reasons , which include _ a ) _ orbital motion , _ b ) _ precession of the nuclear collimator , and _ c ) _ jet instabilities , such as kelvin - helmholtz ( k h ) instabilities , at the jet boundary . * the orbital motion is expected to generate a single oscillation wavelength with fixed amplitude and mirror symmetry of the jet with respect to the core . given the presence of a close bright companion , it has been suggested that the orbital motion might indeed be responsible for the jet wiggles in 3c31 ( blandford & icke 1978 ) and 3c449 ( perley , willis & scott 1979 ) . however no bright companion is visible on the available optical images of 4c+24.36 ( e.g. fig . [ fig : hr_image610 ] ) , thus it seems difficult to ascribe the jet oscillations to the presence of an orbiting system . furthermore , with plausible galaxy masses and the orbital separation required to produce the observed lateral displacement of the jets , the orbital period would be far larger than the jet age allows . * precessional motion is expected to lead to a single oscillation wavelength with amplitude linearly growing with the distance from the nucleus and anti symmetric pattern . given the approximate mirror symmetry of the initial jet oscillations in 4c+24.36 , we can reasonably rule out the precessional model . * confined radio jets are known to be unstable against k h instabilities at their boundary ( hardee 1987 ) . the jet oscillations can be then interpreted as the result of helical motion arising from small perturbations at the jet origin , amplified by growing k h instabilities ( hardee 2003 ; savolainen et al . these instabilities can be triggered for example by random perturbations of the jet flow ( e.g. , by jet cloud interactions ; gmez et al . 2000 ) , or by variation in the jet injection direction from the nucleus ( e.g. , due to the orbital motion of a supermassive binary black hole in the host galaxy ) . it has been shown that the k h helical distortion waves propagating along the jet are able to displace the whole jet and produce large scale helical structures ( hardee 1987 ) . thus k h instabilities are an appealing possibility to interpret the wiggles observed in 4c+24.36 . unfortunately the resolution of our present radio data is not high enough to allow us to determine the characteristics of a possible k h wave propagating along the jet . further information on the fine brightness structure and polarization properties of the jets from higher resolution radio observations would be required to shed light on the possible mechanisms responsible for the oscillations . moreover , forthcoming high resolution x ray _ chandra _ observations ( cycle 9 ) will allow us to carry out a detailed structural comparison of the radio and x ray emission in the jet regions . the investigation of the physical mechanism responsible for the wide angle tail formation poses a number of interesting problems which are not completely understood yet . the earliest models developed for the origin of wats invoked ram pressure resulting from the motion of the associated galaxy through the surrounding intracluster medium ( e.g. , owen & rudnick 1976 ; begelman , rees & blandford 1979 ) . however , wats are usually associated with the central dominant galaxies in groups and clusters , and they are not expected to have large velocities relative to the icm ( burns 1981 ) , as they usually reside at the center of the cluster gravitational potential well ( merritt 1984 ; bird 1994 ) . thus , ram pressure alone seems unable to explain the bends observed in most of the wats ( e.g. , eilek et al . 1984 ; odonoghue , eilek & owen 1993 ) . + one possibility is that if the radio jets are less dense than the external gas , buoyancy forces might contribute to the bending of the tails , as they drag the radio plasma towards lower density regions in the icm ( e.g. , burns & balonek 1982 ) . in real situations , both ram pressure by the galaxy motion and buoyancy are expected to play a role , with buoyancy forces dominant at larger radii ( sakelliou et al . 1996 ) . an alternative scenario is that the large scale bulk motions in the icm , resulting from cluster mergers , may provide the necessary ram pressure to distort the structure of the central dominant radio galaxy ( e.g. , pinkney , burns & hill 1994 ; gmez et al . large scale x ray substructure and merging signatures have been indeed observed in many clusters hosting a wat ( burns et al . finally , an appealing possibility to explain the existence of wats at the center of non merging clusters is the possible connection of the radio source bending with the process of gas sloshing in the cluster core thought to be responsible for the formation of cold fronts ( ascasibar & markevitch 2006 ) . for example , such a connection might be present in a2029 , a very relaxed cluster hosting a wat and a pair of cold fronts at its center ( clarke , blanton & sarazin 2004 ; ascasibar & markevitch 2006 ) . + + the optical and x ray properties of awm4 ( koranyi & geller 2002 and os05 , respectively ) indicate that the cluster has not recently experienced major episodes of merging ( see also sec . [ sec : environment ] ) . moreover , the xmm newton images do not show any sharp surface brightness edges suggestive of the existence of cold fronts in the core ( os05 ) . for these reasons we interpret the bending in 4c+24.36 as a result of the interplay of ram pressure ( driven by the motion of ngc6051 ) and buoyancy forces . following sakelliou et al . ( 1996 ) , we can derive a constraint on the galaxy velocity relative to the icm , as a function of the ratio of the jet density to the icm density , at the point where the components of ram pressure and buoyancy in the direction orthogonal to the jet balance each other ( the _ turnover point _ ) . at smaller distances than this point , the jet bending is expected to be mostly determined by ram pressure , while buoyancy forces dominate at larger distances . furthermore , the bending does not depend on the jet velocity at the turnover point ( sakelliou et al . + we assume that the radio jets can be described as a steady flow of a non relativistic plasma ( bridle & perley 1984 ) , and adopt a coordinate system in which the axes always lie parallel and perpendicular to the jet . at the _ turnover _ point the component of the galaxy velocity in the plane of the sky ( @xmath101 ) can be expressed as ( see sakelliou et al . 1996 , and smoli et al . 2007 for details ) , @xmath102 where @xmath103 is the normal vector to the jet in the plane of the sky , @xmath104 is the unity vector in the direction of the galaxy velocity , @xmath105 is the unity vector in the direction from the cluster center , @xmath82 and @xmath106 are the slope and core radius of the x ray surface brightness when fit to a hydrostatic @xmath82 model , kt is the icm temperature , @xmath107 is the projected distance of the turnover point from the cluster center , h is the width of the jet at this point ( corrected for the resolution of the telescope ) , @xmath59 is the mean molecular weight ( @xmath59=0.6 ) , @xmath108 is the proton mass , and @xmath109 are the density of the jet and icm . a close examination of figs . [ fig : hr_image610 ] and [ fig : profile ] suggests that the last change in direction of the jets ( points e4 and w4 ) might be identified as the turnover point for 4c+24.36 . in this case @xmath110 kpc . the average gas temperature in awm4 is kt=2.5 kev ( tab . 1 ) , and the fit of the radial profile of the cluster x ray surface brightness with a single @xmath82 model provides @xmath111 kpc and @xmath112 ( os05 ) . thus , if @xmath113 kpc , as estimated from fig . [ fig : hr_image610 ] , then from eq . [ eq : vgal ] we can derive the galaxy velocity as a function of @xmath114 ( fig . [ fig : vgal ] ) . in the limit @xmath115 , we obtain an upper limit for the ngc6051 velocity relative to the icm of @xmath116 km s@xmath3 . + we stress that @xmath101 is the velocity component in the plane of the sky , therefore the derived value is a lower limit on the total speed of ngc6051 . on the other hand , the comparison of the ngc6051 redshift to the average redshift of the other cluster members provides an estimate of the line of sight component of its velocity . koranyi & geller ( 2002 ) report a recession velocity of 9703@xmath2946 km s@xmath3 for ngc6051 , and an average velocity for the cluster members within a radius of 0.5 @xmath117 mpc of 9722@xmath2998 km s@xmath3 . thus ngc6051 seems to be relatively at rest with respect to the potential well of awm4 . this is consistent with the fact that the galaxy position is coincident with the peak of the cluster x-ray emission ( koranyi & geller 2002 ; os05 ) , and is also in agreement with the velocities usually found for the dominant galaxies in non merging groups and poor clusters of galaxies ( e.g. , beers et al . 1995 ) . our spectral analysis led us to an estimate of the synchrotron age of 4c+24.36 of @xmath118 myr ( tab . 5 ) . this age is significantly higher than the typical values derived ( using a similar approach to the one adopted in sec . [ sec : parfis ] ) for currently active radio galaxies of similar luminosity , as for example the sources in the b2 sample which have a median age of 16 myr ( parma et al . 1999 , 2007 ) . the age of 4c+24.36 is indeed more similar to the values derived by parma et al . ( 2007 ) for a sample of candidate dying radio galaxies , which have a median age of 63 myr , with values up to 170 myr . + giacintucci et al . ( 2007 ) have recently analysed a sample of cd radio galaxies in rich and poor clusters of galaxies , and found radiative ages @xmath119 years for 4 of the 7 sources with available estimates of the age . they argued that one of them ( a2372 ) is a restarted radio galaxy , where both the new activity and the relic radio plasma from the previous agn burst are visible . another two sources ( a2622 and mkw3s ) are most likely dying radio galaxies , where the nuclear engine has switched off and a relic phase is currently ongoing . however , the total spectral index of 4c+24.36 ( @xmath120 in the 74 mhz10.7 ghz range ) is typical of a currently active radio galaxy rather than a relic source , where @xmath37 can be much steeper ( @xmath1212 ; e.g. parma et al . 2007 ; giacintucci et al . 2007 ) . furthermore , 4c+24.36 clearly shows active nuclear emission at high frequencies ( see insert in fig . [ fig : hr_image610 ] ) . thus it seems rather unlikely that we are dealing with a dying radio galaxy . we would like to point out here that the estimate of the radiative age in tab . 5 is based on the assumption that the energy losses due to the source expansion can be neglected , and that the spectral steepening is due to electron aging in a magnetic field which is constant and uniform across the source . the role of a decreasing magnetic field along the source structure has been considered in alternative models for classical double radio galaxies ( e.g. , blundell & rawlings 2000 , and references therein ) , where the magnetic field decrease is reflected in a steepening of the spectral index , with no direct implication for the source aging . a detailed calculation of the evolution of the electron energy spectrum under the combined effect of radiative losses and adiabatic expansion is difficult , and it is beyond the purpose of the present work . however , we can derive a crude estimate of the effects of possible expansion losses in 4c+24.36 by considering that the cross section of the radio plasma increases by a factor of @xmath12 in the transition from the jets to the lobes ( fig . [ fig : hr_image610 ] ; tab . 3 ) . if we further consider that the inverse compton losses are as important as synchrotron losses ( @xmath122 @xmath59 g ; tab . 5 ) , we may expect that the break energy could be lower by an extra factor of @xmath1 0.6 due to the expansion of the source . moreover , because of the conservation of the magnetic field flux , we would expect a decrease of the magnetic field strength by a factor of @xmath1 0.25 . the combination of these effects would lead to a break frequency which is about one order of magnitude lower with respect to the case in which there is no expansion of the source . as a result , given that @xmath123 ( eq . [ eq : trad ] ) , the age of the source would artificially appear a factor of @xmath1 3 higher than its real value . this implies that in the case of 4c+24.36 , the real age would be of the order of @xmath1 50 myr . thus the age reported in tab . 5 should be considered an upper limit to the real age of the source , and consequently the computed velocity growth as a lower limit .

we find that the source major axis is likely oriented at a small angle with respect to the plane of the sky . the wide angle tail morphology can be reasonably explained by adopting a simple hydrodynamical model in which both ram pressure ( driven by the motion of the host galaxy ) and buoyancy forces contribute to bend the radio structure .

we present a detailed radio morphological study and spectral analysis of the wide angle tail radio source 4c+24.36 associated with the dominant galaxy in the relaxed galaxy cluster awm4 . our study is based on new high sensitivity gmrt observations at 235 mhz , 327 mhz and 610 mhz , and on literature and archival data at other frequencies . we find that the source major axis is likely oriented at a small angle with respect to the plane of the sky . the wide angle tail morphology can be reasonably explained by adopting a simple hydrodynamical model in which both ram pressure ( driven by the motion of the host galaxy ) and buoyancy forces contribute to bend the radio structure . the spectral index progressively steepens along the source major axis from.3 in the region close to the radio nucleus to beyond 1.5 in the lobes . the results of the analysis of the spectral index image allow us to derive an estimate of the radiative age of the source of 160 myr . the cluster x ray emitting gas has a relaxed morphology and short cooling time , but its temperature profile is isothermal out to at least 160 kpc from the centre . therefore we seek evidence of energy ejection from the central agn to prevent catastrophic cooling . we find that the energy injected by 4c+24.36 in the form of synchrotron luminosity during its lifetime is far less than the energy required to maintain the high gas temperature in the core . we also find that it is not possible for the central source to eject the requisite energy in the intracluster gas in terms of the enthalpy of buoyant bubbles of relativistic fluid , without creating discernible large cavities in the existing x ray _ xmm newton _ observations .

0804.1906

i

in this paper we presented a detailed morphological and spectral analysis , at radio wavelengths , of the wat radio galaxy 4c+24.36 , located at the core of the poor galaxy cluster awm4 , based on new high sensitivity observations at 235 mhz , 327 mhz and 610 mhz , using the gmrt , and literature and archival data at other frequencies . the large scale source structure appears bent in a very similar wat morphology at all frequencies , and all resolutions afforded by our gmrt images . we interpret this bending to be the result of the interplay of ram pressure ( driven by the motion of the host galaxy ngc6051 ) and buoyancy forces . in the framework of this model , we estimate that the velocity of the galaxy ngc6051 , with respect to the cluster , is @xmath21 120 km s@xmath3 , in the plane of the sky . combined with the upper limit on the radial velocity of ngc6051 , which is @xmath21 20 km s@xmath3 with respect to the mean radial velocity , out to @xmath124 mpc , of the cluster awm4 ( koranyi & geller 2002 ) , our result indicates that the galaxy is expected to be relatively at rest in the potential well of the cluster . on the small scale , the radio jets show prominent symmetric oscillations within the central @xmath125 kpc from the core . an appealing possibility to explain these features is the development of kelvin helmholtz helical instabilities propagating along the jets . however the resolution of our images is not high enough to investigate the fine structure of the jets , and to determine the characteristics of a possible distortion wave . deep radio observations at higher resolution , combined with polarisation information , are necessary to carry out a more detailed analysis of the jet regions . combining the new gmrt observations , with data from the literature at various other frequencies ( see tab . 4 ) , we derived the broadband radio spectrum of 4c+24.36 , and found that it is well fitted by a power law with @xmath153 between 74 mhz and 10.7 ghz . from the gmrt images at 235 and 610 mhz , evaluating the spectral index distribution at discrete intervals along each jet , we showed ( fig . 7 ) how the spectral index gradually steepens along the jet to about @xmath154 where the jets merge into the lobes , and further steadily steepens within the lobes to @xmath155 . assuming equipartition of energy between the relativistic particles and the ambient magnetic field , and adopting a lower energy cutoff equivalent to the minimum lorentz factor of the radiating electrons ( @xmath156=10 , @xmath157 mev ) , we find that the equipartition value of the magnetic field varies between 3 to 9@xmath59 g from the lobes to the jets . the radiative age for 4c+24.36 was found to be around 160 myr from this estimate . we used the jet to counterjet brightness ratio to constrain the geometry and velocity of the jet . assuming a typical value for the inner jet velocity in wat radio galaxies , we found that the source is likely oriented at a large angle ( @xmath1 81@xmath888@xmath8 ) with respect to the line of sight . this result is consistent with the high level of symmetry found in the total flux density , extent , spectral index properties and physical parameters of the lobes and jets . even though the host cluster awm04 has a hot x ray emitting icm of relaxed morphology and uniform temperature profile out to at least 160 kpc from the center , its cooling time in the core is about 2 gyr , indicating the presence of significant sources of energy injection that prevents the catastrophic cooling expected in the core of the cluster . based on the above values of the jet power and the estimated radiative age , the total energy output from the radio source falls short by almost two orders of magnitude of the energy required for the isothermal temperature profile obtained from the _ xmm newton _ observation of the cluster . the latter observation enables us to measure the pressure of the hot gas as a function of radius within the cluster , which is found to be comparable to the pressure in the jets over most of their lengths , but higher than the pressure in the lobes by a factor @xmath1585 . several interpretations of this pressure imbalance are discussed . finally , it is found that for any reasonable value of gas pressure in the range between the value in the lobes and that in the jets , if the central source were to transfer mechanical energy to the icm , in terms of the enthalpy of buoyant bubbles of relativistic fluid , it would require bubbles of tens of kpc in radius , which would have been detected in the existing xmm - newton observations of osullivan et al . we look forward to a forthcoming deeper _ chandra _ observation of this system for further insight into morphological evidence of this energy transfer . we thank the staff of the gmrt for their help during the observations . gmrt is run by the national centre for radio astrophysics of the tata institute of fundamental research . e.os . acknowledges support from nasa grant nnx06ae90 g . j.m . vrtilek acknowledges support from nasa grant nnx07ae95 g . basic research in radio astronomy at the nrl is supported by 6.1 base funding . we would like to thank r. fanti , g. brunetti and m. markevitch for useful discussion . this research has made use of the nasa / ipac extragalactic database ( ned ) which is operated by the jet propulsion laboratory , california institute of technology . the authors made use of the database cats ( verkhodanov et al . 1997 ) of the special astrophysical observatory ( russia ) . brzan l. , mcnamara b.r . , carilli c.l . , nulsen p.e.j . , wise m.w . , 2006 , in _ heating vs. cooling in galaxies and clusters of galaxies _ , eds . h.bhringer , p.schuecker , g.w . pratt & a. finoguenov ( eso astrophysics symposia ) , ( arxiv : astro - ph/0612393 ) nulsen , p.e.j . et al . , 2006 , in _ heating vs. cooling in galaxies and clusters of galaxies _ , eds . h.bhringer , p.schuecker , g.w . pratt & a. finoguenov ( eso astrophysics symposia ) , ( arxiv : astro - ph/0611136 )

we present a detailed radio morphological study and spectral analysis of the wide angle tail radio source 4c+24.36 associated with the dominant galaxy in the relaxed galaxy cluster awm4 . our study is based on new high sensitivity gmrt observations at 235 mhz , 327 mhz and 610 mhz , and on literature and archival data at other frequencies . the spectral index progressively steepens along the source major axis from.3 in the region close to the radio nucleus to beyond 1.5 in the lobes . the cluster x ray emitting gas has a relaxed morphology and short cooling time , but its temperature profile is isothermal out to at least 160 kpc from the centre . therefore we seek evidence of energy ejection from the central agn to prevent catastrophic cooling . we also find that it is not possible for the central source to eject the requisite energy in the intracluster gas in terms of the enthalpy of buoyant bubbles of relativistic fluid , without creating discernible large cavities in the existing x ray _ xmm newton _ observations .

we present a detailed radio morphological study and spectral analysis of the wide angle tail radio source 4c+24.36 associated with the dominant galaxy in the relaxed galaxy cluster awm4 . our study is based on new high sensitivity gmrt observations at 235 mhz , 327 mhz and 610 mhz , and on literature and archival data at other frequencies . we find that the source major axis is likely oriented at a small angle with respect to the plane of the sky . the wide angle tail morphology can be reasonably explained by adopting a simple hydrodynamical model in which both ram pressure ( driven by the motion of the host galaxy ) and buoyancy forces contribute to bend the radio structure . the spectral index progressively steepens along the source major axis from.3 in the region close to the radio nucleus to beyond 1.5 in the lobes . the results of the analysis of the spectral index image allow us to derive an estimate of the radiative age of the source of 160 myr . the cluster x ray emitting gas has a relaxed morphology and short cooling time , but its temperature profile is isothermal out to at least 160 kpc from the centre . therefore we seek evidence of energy ejection from the central agn to prevent catastrophic cooling . we find that the energy injected by 4c+24.36 in the form of synchrotron luminosity during its lifetime is far less than the energy required to maintain the high gas temperature in the core . we also find that it is not possible for the central source to eject the requisite energy in the intracluster gas in terms of the enthalpy of buoyant bubbles of relativistic fluid , without creating discernible large cavities in the existing x ray _ xmm newton _ observations .

1003.0020

c

we report in this paper on the properties of a peculiar and unique source at z=0.359 , cid-42 , in a survey of x - ray sources with acs counterparts in cosmos . cid-42 is a unique source in three specific ways . first , in the 2 deg@xmath6 cosmos area , there are @xmath14 x - ray sources out of @xmath1550 at z@xmath40.8 with optical morphologies indicative of ongoing major mergers , but only one of them ( cid-42 ) clearly shows two cores resolved in the hst image embedded in the same galaxy but unresolved in x - rays . the surface brightness decomposition applied to the acs image strongly suggests the presence of a point like unresolved source ( se source ) and a more extended , but still compact , source ( nw source ) . the tidal tails to the ne and sw , in the acs image , are evidence of merging ( toomre & toomre 1972 , dubinski et al . 1999 , springel & white 1999 ) . the morphology is consistent with either a early passage state , in a phase subsequent to the first passage , or with a later stage of the merging after the coalescence of the two bhs ( mihos & hernquist 1996 , cox et al . 2006 , hopkins et al . 2008 ) . second , in 3 optical spectra obtained with two different instruments ( vimos and imacs ) a velocity offset larger than 1000 km / s is measured between the broad and narrow component of h@xmath2 line . large velocity offsets between two different line systems can be observed if two bhs in a virialized system are rapidly rotating very close to each other ( sub - parsec separation ) , as suggested for the double line system of boroson & lauer ( 2009 ) . however , assuming that the broad and narrow lines are coming from the se and nw sources respectively , virialization is not appropriate for the kiloparsec scale separation of the two sources in cid-42 . a possibility to justify the large velocity offset is a recoil effect . large recoiling velocity have been predicted by theoretical models and simulations for both gw wave kicks ( campanelli et al . 2007a , b ) and slingshot effect kicks in triple bh systems ( hoffman & loeb 2007 ) . the unresolved morphology of the se source allows us to assume that it plays the role of the unobscured smbh ( a type 1 agn ) and produces the broad h@xmath2 line . therefore the se source is recoiling with respect to the system with a velocity of @xmath131000 km / s . as the bh recoils from the center of a galaxy or from another bh , the closest , most tightly bound , regions ( disk and blrs ) are carried with it , and the more distant regions ( nlrs ) are left behind ( loeb 2007 ) . given the distance between the recoiling bh and the center of the whole system ( measured on the plane of the sky ) and one component of the bh velocity ( the radial velocity ) with respect to the galaxy , it is possible to compute a lower limit on the time since the bh has been kicked of @xmath14@xmath510@xmath92 yr . the detection of a recoiling bh is related to its lifetime and it is extremely rare because it never gets large separation before fading . the lifetime of the active phase of the bh depends on the amount of accreting material it carries after the kick . in principle , higher velocities result in a smaller ejected disc . in cid-42 , the bh is still emitting enough radiation to ionize the blr , so it had to carry enough material in order to be still active . it is possible to compute the bh mass of se source using the relation of vestergaard & peterson ( 2006 ) between the line width , the bh mass and the continuum luminosity , by using the h@xmath2 line width ( 3500@xmath0233 km / s ) . as shown in figure [ sed ] , the total continuum luminosity is mostly dominated by the galaxy light . taking advantage of the surface brightness decomposition results , we can extrapolate the 5100 nuclear luminosity of @xmath14@xmath510@xmath29 erg s@xmath16by normalizing a standard quasar template ( red line in fig . [ sed ] , elvis et al . 1994 ) to the se source luminosity in the acs filter ( square in fig . [ sed ] ) . under this assumption , the bh mass of the se source is @xmath16.5@xmath510@xmath93 m@xmath22 . given the total mass of the galaxy and the estimated bh mass , the ratio m@xmath94/m@xmath95 is a factor 2 higher than the hring & rix ( 2004 ) m@xmath94-m@xmath95 relation for local spheroids . although the errors on the bh and galaxy mass are quite large , this is consistent with the fact that cid-42 is a peculiar source or that the local relation deviates at high z ( see for example treu et al . 2007 and merloni et al . 2010 ) . if we consider that the galaxy mass is an upper limit to the bulge mass , the offset from the relation could be even bigger . using the bolometric luminosity and bh mass of the se source , we find that the eddington ratio is l / l@xmath960.04 , consistent either with the nuclear activity of this source having just been triggered or already declining . using the correlation between the eddington ratio and the bolometric correction in the 2 - 10 kev energy range ( vasudevan & fabian 2009 , young et al . 2010 ) , it is possible to estimate the 2 - 10 kev luminosity emitted by the se source to be in the range 0.6 - 1@xmath510@xmath29 erg s@xmath16 , consistent with the 2 - 10 kev luminosity measured for cid-42 ( see table [ xray ] ) . the third feature which makes cid-42 unique is the detection , in the x - ray spectra , of an extraordinarily strong , _ redshifted _ absorption iron line and an emission iron line , forming an _ inverted _ p - cygni profile . out of the 100 x - ray sources with more than 1000 counts in the stacked x - ray spectrum only cid-42 shows an iron line in absorption ( mainieri et al . 2007 , lanzuisi et al . 2010 in prep . ) . the absorption line is intrinsically narrow . its energy centroid changes by 500 ev over the 4 years of observations . the broadening of the absorption line in the total spectrum is the result of the stacking of narrow lines redshifted by different velocities in the different observations . such _ redshifted _ absorption lines are rare . most known x - ray absorbers in agns are blueshifted ( see cappi 2006 for a review ) and 85% of them are at low redshift ( z@xmath40.2 ) . as blueshifted absorbers necessarily imply out - flowing winds , redshifted absorbers would seem to require high velocity inflows , which must therefore be situated very close to the central black hole . the few convincing cases of redshifted lines are all narrow absorption lines detected in seyfert 1 sources ( mrk 335 , longinotti et al . 2007 ; pg 1211 + 143 , reeves et al . 2005 ; mrk 509 , dadina et al . 2005 ) , and have suggested explanation as gas falling with relativistic velocity directly into the bh at a few tens of gravitational radii . the cluster of rare features seen in this source , more likely associated with a brief moment of the merging event , is a strong argument against the chance superposition hypothesis . any model for the system should preferably link these unique features . we describe two possible models below . the spatial offset of the se point - like source with respect to the nw source and the kinematic offset of the broad h@xmath2 line with respect to the narrow line system can be explained by a smbh ejected by gravitational radiation produced in the black hole merger . according to theoretical models , during the final coalescence of two bhs in a merger event , the gravitational waves produced can impart a large kick to the resultant bh , which recoils in the opposite direction with respect to the center of the galaxy ( peres 1962 ) . although some approximate methods indicated that the kick velocities are most likely small ( @xmath4few@xmath5100 km / s , blanchet et al . 2005 , damour & gopakumar 2006 ) , the results from full numerical relativity simulations show that the recoil speed can be up to 4000 km / s ( campanelli et al . 2007a , b ) . it is difficult to estimate how often significant recoil kicks occur , because the recoil kick distribution depends on the spin and mass ratio distributions of the progenitor bh binaries , which are not well known . several authors ( schnittman & buonanno 2007 , campanelli et al . 2007a , b and baker et al . 2008 ) estimated , using results from full numerical relativity simulations , that 12 - 36% of recoiling bhs will have velocities @xmath13 500 km / s and 3 - 13% @xmath97 1000 km / s , assuming a spin of 0.9 with random orientations and using different assumptions on how the kick velocity scales with bh progenitor mass ratio ( 0.1@xmath981 ) . these fractions might be smaller if bh spins are on average lower or if gas torques are efficient at aligning the spin axes in a way that is unfavorable for large kicks ( bogdanovic et al . 2007 , dotti et al . 2009 ) . to constrain the actual recoil kick distribution , better observational constraints on merging bhs or observations of individual recoiling bhs are required . a candidate recoiling smbh with a large kick velocity of 2650 km / s has been spectroscopically discovered by komossa et al . ( 2008 ) , although alternative models have been proposed to explain the two systems of lines in the optical spectrum . a second possible candidate has been also proposed by shields et al . ( 2009 ) . the high velocity offset ( v@xmath131000 km / s ) measured in the optical spectra of cid-42 is consistent with the numbers obtained in simulations , although the probability of finding such high velocity recoiling bh is low ( @xmath410% ) . the surface brightness decomposition of the cid-42 acs image is consistent with the ejected bh hypothesis too : the se point - like source , the ejected bh , is spatially separated from the compact , but not point - like , nw bright source , which can easily represent the galaxy core from which the bh has been ejected . the fact that the broad lines are redshifted with respect to the stellar absorption lines is consistent with the recoiling bh picture , because they are following the bh , as explained at the beginning of section 5 . the narrow lines in the spectra have the same redshift of the stellar absorption lines but , given that the nlrs , residing in the nw source , are not powered anymore by the bh and will fade long before the ejected bh reaches kpc distances , another way to produce the narrow lines is needed . the line flux ratios indicate that the emission is produced by nuclear activity and not by star formation ( comerford et al . the narrow lines could be produced by the ejected bh ionizing the local galaxy ism on its way out from the center . in this case , the narrow lines should have the same redshift of the galaxy , as observed , implying that the bh is still inside a region of the galaxy disk with high ism density or is passing by molecular clouds . in this case , the velocity offset measured in the optical spectrum , not corrected for instrumental shift ( see section 4.1 ) , is 1360@xmath0320 km / s , which represents the radial component of the total velocity . lousto et al . ( 2009 ) showed in a statistical studies of black - hole binaries during the inspiral and merger , that when the kick velocity is @xmath991000 km / s , the direction of the kick is most likely perpendicular to the bh orbital plane . they found a probability of 6.3% for large recoil velocities ( @xmath131000 km / s ) along the line of sight . if the accretion disk is aligned with the nearly face - on galaxy disk as a whole , then a large kick closely aligned with the line of sight is expected , and it is consistent with what observed in cid-42 , if the source is a recoiling bh . the time since the bh has been kicked ( @xmath14@xmath510@xmath92 yr ) , as computed at the beginning of section 5 , is in agreement with the prediction of the effective time for the persistence of off - center quasar activity ( 10@xmath100 yr , blecha & loeb 2008 ) . this number is a lower limit but it should be a good estimate , assuming that the total kick velocity is not much higher than the radial velocity , given that this is already in the extreme tail of the kick velocity distribution predicted by models and simulations . according to blecha & loeb ( 2008 ) model , for a kick velocity in the range 1100 - 1500 km / s and a bh mass of 10@xmath93 - 10@xmath101 m@xmath22 , the mass of the bh disc , in order to be still emitting , is @xmath12 - 3% of the bh mass . models predict that the effect on galaxy morphology of bh recoil is to produce significant asymmetry ( kornreich & lovelace 2008 ) . this is seen in the morphology of cid-42 where the galaxy core ( the nw source ) is slightly misplaced with respect to the geometric center of the galaxy disc . the variable fe - k absorption line can be alternatively explained , as already explained at the beginning of this section , by material inflowing into the bh , as it has been proposed in a few other sources ( cappi 2006 , see section 5 ) . in order to have such a high velocity , the inflow of material would have to be very close to the nucleus ( few tens of schwarzschild radii ) . one means of achieving high inflow velocity is with a photon bubble instability ( arons 1992 , gammie 1998 , begelman 2006 ) which produces a propagating pattern of low and high density regions through which the radiation has to go . the photon bubble instability is currently used to explain the _ inverted _ p - cygni profiles detected in the spectra of luminous blue variable ( lbv ) stars ( e.g. , van marle et al . although this would be a physical explanation , it requires super - eddington accretion , that is not observed in cid-42 . although the high velocity inflow possibility is very interesting , without a detailed modeling it remains mere hypotheses . in the following we list the evidences in favor of a picture in which cid-42 contains 2 agns , an unobscured type 1 agn in the se source and an obscured type 2 agn in the nw one . 1 . the surface brightness decomposition of the acs image finds a compact , but not point - like , bright source in the nw nucleus . 2 . the shift ( @xmath1021180 @xmath0360 km / s ) between the broad and narrow components of the h@xmath2 line in the optical spectrum also suggests the presence of two active nuclei , one responsible for the broad line emission ( i.e. a type 1 agn ) , the second responsible for the narrow emission lines only ( i.e. a type 2 agn ) . a possible explanation for the presence of only one narrow emission line system could be that the narrow line regions ( nlrs ) of the two sources are mixed up , and , for this reason , are at the same redshift measured for the galaxy from the absorption lines . however , we discard this hypothesis as nlrs , at the luminosity of cid-42 , are expected to extend 0.1 - 1 kpc from the nucleus ( schmitt et al . 2003 ) , much less than the projected separation measured between cid-42 nuclei . 3 . the x - ray flux variability , and the presence of a strong iron emission line ( ew@xmath1500 ev ) when the continuum is weak also suggest a combination of a variable type 1 agn and a constant obscured type 2 agn . usually , strong iron emission lines ( ew@xmath11kev ) are associated with heavily obscured ( compton thick ) sources and are less prominent in unobscured ones ( ew@xmath1150 ev ; e.g. , see figure 9 of guainazzi et al . 2005a ) . as already noted by guainazzi et al . ( 2005b ) , all the agn pairs observed so far are found to be heavily obscured or compton thick in the x - rays , in both components . the presence of at least one obscured agn in our system is consistent with this picture but the possibility that we have a type 2 plus a type 1 agn embedded in the same galaxy is new , although we believe cid-42 is not a binary . assuming that the [ oiii ] emission lines are produced by the type 2 agn only , it is possible to roughly estimate the contribution of the two sources to the total x - ray luminosity . the type 2 luminosity is estimated from the relation between the l@xmath103-l@xmath104}$ ] measured in the cosmos field ( silverman et al . 2009 ) and the type 1 agn luminosity is then found by subtraction . given the [ oiii ] luminosity ( @xmath13@xmath510@xmath105 erg s@xmath16 ) and the uncertainties on this relation , the luminosity of the nw type 2 nucleus would be @xmath19@xmath510@xmath39 erg s@xmath16 in the 2 - 10 kev band . the derived type 1 agn luminosity ( 2 - 10 kev ) is in the range 0.3 - 1.8@xmath510@xmath29 erg s@xmath16 , due to the strong measured variability ( fig . [ sed ] , right ) . the last number is consistent with the 2 - 10 kev luminosity obtained in the previous section with the eddington ratio . as explained at the beginning of section 5 , the large velocity shift between the two nuclei implied by the optical spectra would require a large mass of the system assuming it is virialized ( i.e. the two nuclei are gravitationally bound in a circular orbit ) . comerford et al . ( 2009 ) detected two sets of [ oiii ] and h@xmath42 lines in a keck / deimos spectrum , from which a @xmath3v=150 km / s is measured by detecting two sets of emission line . this lower velocity shift allows a more `` reasonable '' mass for a virialized system , however , virialization , which is a fair assumption for close pairs , is probably not appropriate for the kiloparsec scale separation of the two cid-42 sources . most likely , the velocity measured by comerford et al . ( 2009 ) is due to the rotation of the gas in the galaxy as a whole , as the system is in a violent state of gravitational interaction . the large velocity offset between the two source is more likely due to a nearly radial orbit , with the type 1 se agn is recoiling with respect to the type 2 agn . a velocity difference of this size may result from a slingshot ejection in a triple bh encounter ( saslaw et al . 1974 , hoffman & loeb 2006 , 2007 ) . if a bh binary stalls for a time of @xmath1 few gyrs before it coalesces , due to the depletion of stars in the loss cone in a gas poor merger ( merritt & milosavljevic 2005 ) , its host galaxy could merge with another galaxy and a third bh may spiral in and undergo a strong 3-body interaction with the binary . the just arrived system will merge with the original galaxy . the star formation rate ( @xmath1100 m@xmath22/yr ) measured from the sed fitting , supports the scenario of a merger in a early phase . the merger will drive mass and gas to the binary , refilling its loss cone . the configuration will become gravitationally unstable and this event will end with the further reduction of the separation or the coalescence of the binary and the ejection of the lightest body at a speed comparable to the binary s orbital speed ( heggie 1975 ) . the large projected distance ( 2.4 kpc ) between the two sources and the high velocity measured in in cid-42 are possible for this kind of ejection ( hoffman & loeb 2006 , 2007 ) , although the probability to have a certain velocity depends from the initial condition of the system and a proper modeling is still undergoing . on the basis of the above analysis , the se nucleus is the unobscured type 1 recoiling agn , while the nw is an obscured type 2 agn , resulting from the coalescence of a binary . the two nuclei lie close to the plane of the sky possibly moving on a radial orbit in a direction close to the line of sight , though a small angle has to be considered given the 2.4 kpc separation . relative to the mean velocity of the system , the se nucleus is moving away from the observer and the nw one towards the observer . the suggested geometry of the system is shown in figure [ model ] . the se type 1 nucleus then has : a strong unobscured optical continuum and blr , leading to the point - like hst / acs image , the broad h@xmath2 emission line and a strong , variable , x - ray continuum emission . the obscured nw type 2 nucleus has : a weak optical continuum , leading to a compact but extended hst / acs source dominated by the galaxy light , only narrow emission lines of h@xmath2 and [ oiii ] , and a weak x - ray continuum , with a strong fluorescent iron emission line ( ew@xmath106 570 ev ) . the proximity of the two sources allows a special interpretation of the fe - k absorption line as a `` backlit wind '' . in this scenario , a fast , highly ionized bal - like wind is emitted by the nw type 2 nucleus ( located in front ) . in almost all circumstances this wind would be undetectable . however , in the case of cid-42 , the _ receding _ wind crosses our line of sight to the se type 1 nucleus , leading to absorption of the type 1 continuum in redshifted iron . the blueshifted emission of the approaching wind remains invisible as there is no background source to illuminate it . the column density of the flow derived from the ew of the absorption line is consistent with what is seen in bal wind ( @xmath1310@xmath53 @xmath54 ; green et al . 2001 , gallagher et al . 2002 , chartas et al . the fact that we measure no x - ray photoelectric absorption at low energies implies that the wind is highly ionized , something observed also in other bal ( e.g. , telfer et al . 1998 , hamann 1998 , chartas et al . 2009 ) and x - ray absorbers ( e.g. , vignali et al . 2000 , reeves et al . 2009 ) . the variations of the iron absorption line energy centroid on years timescale can be explained either by velocity variations ( @xmath110,000 km / s per year ) in the flow , or by a change in the ionization state , and so in the density ( proga et al . 2000 ) or , possibly , to a precession of the flow , so that a change in inclination can produce a difference in velocity , or by a combination of all these effects . bals , where we look directly along the flow , are known to vary on year timescales ( e.g. , lundgren et al . 2007 , gibson et al . 2008 ) , so variability should be more likely in a section viewed across the flow . the variability implies that the bal - like flow must be highly structured , even 2.5 kpc away from the nucleus . this is not unusual as it has been shown by detection of radio jets still relativistic at mpc distance from their origin ( e.g. , pks 0637 - 752 , schwartz et al . 2000 ) . as we have only one example of _ redshifted _ iron absorber and only one recoiling bh , this scenario is only plausible if the bal - like wind has a large opening angle , making an interception of the rear recoiling type 1 nucleus likely . winds at a few 1000 km / s are normal in type 1 agns ( reynolds 1997 , piconcelli et al . 2005 ) and much faster ( 0.1 - 0.2@xmath58 ) bal winds , confined to modest solid angles , are not unusual ( weymann et al . 1991 , hamann et al . 1993 , ogle et al . fast winds at kpc - scale distances from type 1 agn have been found as well ( arav et al . 2001 ) and have been proposed to be universal in agns ( elvis 2000 ) . however , there has been no possibility to test this idea in type 2 agns . cid-42 provides this opportunity and gives us the first detection of a wind in a type 2 agn .

we present a detailed study of a peculiar source detected in the cosmos survey at z=0.359 . a large ( km / s ) velocity offset between the narrow and broad components of h has been measured in three different optical spectra from the vlt / vimos and magellan / imacs instruments . cid-42 is also the only x - ray source in cosmos having in its x - ray spectra a strong _ redshifted _ broad absorption iron line , and an iron emission line , drawing an _ inverted _ p - cygni profile . , the x - ray absorption line can be explained as a bal - like outflow from the foreground nucleus ( a type 2 agn ) at the rearer one ( a type 1 agn ) , which illuminates the otherwise undetectable wind , giving us the first opportunity to show that fast winds are present in obscured agn , and possibly universal in agns .

we present a detailed study of a peculiar source detected in the cosmos survey at z=0.359 . source cxoc j100043.1 + 020637 , also known as cid-42 , presents two compact optical sources embedded in the same galaxy . the distance between the two , measured in the hst / acs image , is 0.495``.005 '' that , at the redshift of the source , corresponds to a projected separation of 2.46.02 kpc . a large ( km / s ) velocity offset between the narrow and broad components of h has been measured in three different optical spectra from the vlt / vimos and magellan / imacs instruments . cid-42 is also the only x - ray source in cosmos having in its x - ray spectra a strong _ redshifted _ broad absorption iron line , and an iron emission line , drawing an _ inverted _ p - cygni profile . the and data show that the absorption line is variable in energy bye=500 ev over 4 years and that the absorber has to be highly ionized , in order not to leave a signature in the soft x - ray spectrum . that these features , the morphology , the velocity offset and the _ inverted _ p - cygni profile , occur in the same source is unlikely to be a coincidence . we envisage two possible explanations , both exceptional , for this system : ( 1 ) a gravitational wave recoiling black hole ( bh ) , caught 1 - 10 myr after merging , ( 2 ) a type 1/ type 2 system in the same galaxy where the type 1 is recoiling due to slingshot effect produced by a triple bh system . the first possibility gives us a candidate gravitational waves recoiling bh with both spectroscopic and imaging signatures . in the second case , the x - ray absorption line can be explained as a bal - like outflow from the foreground nucleus ( a type 2 agn ) at the rearer one ( a type 1 agn ) , which illuminates the otherwise undetectable wind , giving us the first opportunity to show that fast winds are present in obscured agn , and possibly universal in agns .

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we have reported the multiwavelength properties of cid-42 , which presents three unusual features : two close sources , embedded in the same galaxy , resolved in the optical acs image , but unresolved in the x - ray one , a high velocity offset , measured between the broad and narrow h@xmath2 lines in 3 different optical spectra and a _ redshifted _ absorption iron line in the x - ray spectrum . thanks to the rich database of the cosmos survey , the analysis of the properties of cid-42 has been performed at all wavelengths . the overall analysis suggests two possible explanations for the source : a gw recoiling bh , caught @xmath1few myr after the kick from the center of the galaxy or a type 1/type 2 agn system where the type 1 is recoiling due to a slingshot effect . analysis of the acs image shows the presence of a se point - like source , playing the role of the type 1 agn ( or smbh with disc and blrs ) in both scenarios , confirmed by the x - ray flux variability across the time and by the offset in velocity measured between the narrow and the broad components of the h@xmath2 line . the nw source , being less compact than the se one , could be either the naked core of the galaxy from which a bh has been kicked out or a type 2 agn . the presence of a _ redshifted _ absorption iron line changing its energy centroid in the different observations , allows to explain the geometry of the system by inflow of material into the bh in the gw recoil bh case or with the `` backlit wind '' model in the second scenario . monitoring observations in the x - ray would be suitable to study the moving x - ray absorption feature and its variability . the `` backlit wind '' implies that fast bal - like winds are present in type 2 agns , an otherwise untestable hypothesis . the variability of the iron absorption is , in this special case , a new tool to study bal flows . this model predicts corresponding high ionization uv absorption lines ( e.g. ovi ) , making cid-42 a suitable target for hst / cos observations . high - resolution observations with hrc could resolve the two sources to see if both are x - ray emitting or not , while optical and ir spectroscopy with higher spatial resolution , which currently is only possible with hst , could confirm the still uncertain velocity shift measured in h@xmath2 in other lines . if future observations allow us to confirm that the gw recoiling bh is the best explanation of the system , it will be the first time in which this phenomenon is observed via both spatially offset from the galactic core and a velocity offset in the optical spectrum . although models for this system have been sketched qualitatively in this paper , a numerical analysis will be the subject of a forthcoming paper . upcoming keck integral field unit ( ifu ) observations with osiris will help us to disentangle major competing models mapping the inner region of cid-42 . ifu observations on larger scales could map the velocity of gas and stars in the galaxy and in the tails , in order to constrain the theoretical models on the geometry of the merger and the inclination of the galaxies in the first encounter ( donghia et al . in prep . ) . calibrating the number of recoiling bh , produced either in close triple encounters and by gravitational waves ejection could be of great importance for the proposed laser interferometer space antenna ( lisa ) mission ( see discussion in loeb 2009 ) . cid-42 is a unique source with a cluster of rare features . whichever is the best explanation , in cid-42 we are witnessing a runaway bh

source cxoc j100043.1 + 020637 , also known as cid-42 , presents two compact optical sources embedded in the same galaxy . we envisage two possible explanations , both exceptional , for this system : ( 1 ) a gravitational wave recoiling black hole ( bh ) , caught 1 - 10 myr after merging , ( 2 ) a type 1/ type 2 system in the same galaxy where the type 1 is recoiling due to slingshot effect produced by a triple bh system . the first possibility gives us a candidate gravitational waves recoiling bh with both spectroscopic and imaging signatures . in the second case

we present a detailed study of a peculiar source detected in the cosmos survey at z=0.359 . source cxoc j100043.1 + 020637 , also known as cid-42 , presents two compact optical sources embedded in the same galaxy . the distance between the two , measured in the hst / acs image , is 0.495``.005 '' that , at the redshift of the source , corresponds to a projected separation of 2.46.02 kpc . a large ( km / s ) velocity offset between the narrow and broad components of h has been measured in three different optical spectra from the vlt / vimos and magellan / imacs instruments . cid-42 is also the only x - ray source in cosmos having in its x - ray spectra a strong _ redshifted _ broad absorption iron line , and an iron emission line , drawing an _ inverted _ p - cygni profile . the and data show that the absorption line is variable in energy bye=500 ev over 4 years and that the absorber has to be highly ionized , in order not to leave a signature in the soft x - ray spectrum . that these features , the morphology , the velocity offset and the _ inverted _ p - cygni profile , occur in the same source is unlikely to be a coincidence . we envisage two possible explanations , both exceptional , for this system : ( 1 ) a gravitational wave recoiling black hole ( bh ) , caught 1 - 10 myr after merging , ( 2 ) a type 1/ type 2 system in the same galaxy where the type 1 is recoiling due to slingshot effect produced by a triple bh system . the first possibility gives us a candidate gravitational waves recoiling bh with both spectroscopic and imaging signatures . in the second case , the x - ray absorption line can be explained as a bal - like outflow from the foreground nucleus ( a type 2 agn ) at the rearer one ( a type 1 agn ) , which illuminates the otherwise undetectable wind , giving us the first opportunity to show that fast winds are present in obscured agn , and possibly universal in agns .

1409.1076

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thin sheets with repetitive metallic inclusions or exclusions have been used extensively in the past in antenna applications to control the properties of reflected or transmitted power , e.g. its direction , phase , or polarization @xcite . such surfaces have received increasing attention lately , as part of the intensive research in the field of optical and microwave metamaterials , in an attempt to harness ideas from bulk metamterial explorations to design low - profile components with extraordinary wavefront manipulation capabilities @xcite . in contrast to bulk metamaterials , where subwavelength elements are combined to form a volumetric entity with prescribed local response to electromagnetic fields , in metamaterial sheets , or metasurfaces , these subwavelength atomic units are confined to a region with subwavelength thickness . this geometrical difference should decrease significantly fabrication complexity of metasurfaces and also loss - related problems ; however , it requires development of new design methodologies , as the interaction of electromagnetic fields with metasurfaces is naturally described via effective boundary conditions @xcite , as opposed to effective permeabilities and permittivities ( or effective wave equations ) , more suitable for modelling volumetric metamaterials @xcite . in particular , it was recently recognized that as metasurfaces act as sources of tangential field discontinuities , they can be modelled by a distribution of electric and magnetic surface currents , prescribed by the equivalence principle [ , pp . 575 - 579 ] . hence , in principle , for a given incident field , a desirable electromagnetic field distribution in space can be achieved by engineering the surface to induce currents that would produce the required tangential fields on both of its facets . approximating the required continuous surface currents by a dense distribution of electric and magnetic dipoles , passive surfaces implementing plane - wave refraction were demonstrated @xcite . the elementary sources were formed by subwavelength inductive and capacitive elements that produced the suitable magnitudes of the current in response to the exciting incident plane - wave . simultaneously , it was demonstrated that also active elementary sources may be utilized to introduce desirable field discontinuities , e.g. , to implement a cloaking device based on the same equivalence principle @xcite . as these surfaces were composed of orthogonal electric and magnetic dipoles engineered to induce unidirectional radiation , i.e. acting as huygens sources [ , pp . 653 - 660],@xcite , they were named huygens metasurfaces ( hms ) @xcite . in addition to plane - wave refraction and cloaking , recent reports proposed designs of huygens metasurfaces which implement beam shaping , transmission or reflection coefficient engineering and polarization manipulation ( using tensor huygens metasurfaces ) @xcite . although the design methodologies differ between the various authors , they all rely on the fact that if the dimensions of the unit cells and their spatial arrangement obey certain conditions , the metasurface can be modelled by effective electric and magnetic polarizability distributions , which are translated to position - dependent sheet boundary conditions @xcite . these , in turn , can be equivalently described as surface impedance and surface admittance matrices relating the electric and magnetic field components at the two facets of the metasurface @xcite . following this approach greatly simplifies device design , as it facilitates the development of simple circuit models to huygens metasurfaces @xcite . moreover , as the effective surface impedance and admittance matrices are directly related to the _ locally averaged _ polarizabilities of the elementary scatterers , we may assess the local equivalent surface impedance of a unit cell by simulating or measuring the effective impedance of an infinite periodic array of such identical unit cells ( local periodicity approximation ) @xcite . indeed , this modelling approach was used in recent demonstrations of hmss : given the incident field and the desirable transmitted ( or reflected ) field , the required boundary conditions to support the field discontinuities can be formulated , resulting in the required surface impedance and admittance matrices ( or electric and magnetic polarizability distributions ) . however , for realizing the huygens metasurfaces , it is desirable for the elements implementing the required polarizability distributions to be passive and lossless , i.e. the surface impedance and admittance to possess pure imaginary values . implementing impedance or admittance sheets with nonvanishing real parts requires engineering of gain or loss elements , thereby complicating greatly the design and realization . nonetheless , following the simplistic methodology in which the discontinuities between the desirable and incident fields are directly translated into surface impedances and admittances by no means guarantees the passivity of the resultant metasurface ( see , e.g. , @xcite ) . in fact , in @xcite the design procedure did not consider the passivity limitation , however the resultant leading to a well - functioning , prototype . the reasons for that encouraging outcome were not analyzed therein , though . in addition , almost all huygens metasurfaces presented in the literature to date were designed to be excited by a plane - wave or a beam propagating towards the surface in homogeneous medium @xcite . nevertheless , to facilitate the development of realizable antenna devices based on huygens metasurfaces it would be necessary to extend the current design techniques to enable excitation of the metasurface by localized ( impulsive ) sources , or waveguided modes . a step in that direction was made by holloway _ @xcite , where a line source excitation was considered , but only for metasurfaces with _ constant _ polarizability density ; as demonstrated by @xcite , allowing the polarizability densities to vary along the metasurface could be beneficial , providing more degrees of freedom for the design . in this work , we derive simple rules for designing passive lossless huygens metasurfaces producing directive radiation to a prescribed angle when excited by a given ( arbitrary ) source field . decomposing the fields to their plane - wave spectrum and generalizing the approach presented in @xcite for plane - wave excitation , we show that satisfying two physical conditions is sufficient to guarantee that the desirable functionality can be achieved by purely reactive surfaces : local power conservation across the surface , and local impedance the fields on both sides of the metasurface . enforcing these conditions locally , i.e. at each point on the surface , leads to a complementary set of simple expressions for the surface impedance and surface admittance , as well as facilitates the semi - analytical evaluation of the reflected and transmitted fields . these results enable design of directive hms radiators with a wide range of source excitations , thus extending significantly the possible applications . moreover , the derivation provides clear physical interpretation of the conditions required to implement passive lossless hmss , which may also be indicative to equivalent requirements in more generalized scenarios ( e.g. hmss which perform other functionalities ) . altogether , this forms an efficient and powerful tool for hms engineering , promoting design of novel antenna devices .

we present a formulation of the interaction between a given source field and a scalar huygens metasurface ( hms ) , a recently introduced promising concept for wavefront manipulation based on a sheet of orthogonal electric and magnetic dipoles . utilizing the equivalent surface impedance representation of these metasurfaces , we establish that an arbitrary source field can be converted into directive radiation via a passive lossless hms if two physical conditions are met : local power conservation and local impedance . expressing the fields via their plane - wave spectrum and harnessing the slowly - varying approximation we obtain semi - analytical formulae for the scattered fields , and prescribe the surface reactance required for the metasurface implementation . , the proposed formulation also provides a mechanism to incorporate a variety of source configurations into general hms models , as well as physical insight on the conditions enabling purely reactive implementation of this novel type of metasurfaces . epstein and eleftheriades : passive lossless huygens metasurfaces for directive radiation metasurfaces , huygens sources , wavefront manipulation , plane - wave spectrum .

we present a formulation of the interaction between a given source field and a scalar huygens metasurface ( hms ) , a recently introduced promising concept for wavefront manipulation based on a sheet of orthogonal electric and magnetic dipoles . utilizing the equivalent surface impedance representation of these metasurfaces , we establish that an arbitrary source field can be converted into directive radiation via a passive lossless hms if two physical conditions are met : local power conservation and local impedance . expressing the fields via their plane - wave spectrum and harnessing the slowly - varying approximation we obtain semi - analytical formulae for the scattered fields , and prescribe the surface reactance required for the metasurface implementation . the resultant design procedure indicates that the local impedance induces a fresnel - like reflection , while local power conservation forms a radiating virtual aperture which follows the total excitation field magnitude . the semi - analytical predictions are verified by finite - element simulations of hmss designed for different source configurations . besides serving as a flexible design procedure for hms radiators , the proposed formulation also provides a mechanism to incorporate a variety of source configurations into general hms models , as well as physical insight on the conditions enabling purely reactive implementation of this novel type of metasurfaces . epstein and eleftheriades : passive lossless huygens metasurfaces for directive radiation metasurfaces , huygens sources , wavefront manipulation , plane - wave spectrum .

0812.0306

i

the recently discovered `` -loud '' binaries ( grlb ) form a new sub - class of galactic binary star systems which emit gev - tev s @xcite . these are high mass x - ray binaries ( hmxrb ) composed of a compact object ( a black hole or a neutron star ) orbiting a massive star . the detection of s with energies up to 10 tev from these systems shows that certain hmxrbs host powerful particle accelerators producing electrons and/or protons with energies above 10 tev . at the moment it is not clear which physical process leads to the very high energy ( vhe ) particle acceleration and whether the vhe particle acceleration is a generic feature of the hmxrbs or the result of specific physical conditions in a restricted hmxrb sub - class . it is possible that particle acceleration is taking place in a large number of x - ray binaries , but the s can be detected only from the objects with preferred orientations w.r.t . the line of sight ( e.g. with jets pointing toward the observer ) @xcite . alternatively , it may be that the conventional accretion - powered binaries are not capable of accelerating particles and that the activity of a binary is powered by a different mechanism ( see e.g. @xcite ) . the theoretical models of activity of hmxrbs @xcite all assume emission from the interaction of a relativistic outflow from the compact object ( jet from a black hole , or wide angle wind from a pulsar ) with the wind and radiation emitted by the companion massive star . the basic properties of the outflows , such as the composition ( e@xmath1e@xmath2 pairs or electron - nuclei plasma ) , anisotropy ( a collimated jet or a wide angle outflow ) etc . are as yet poorly constrained by the data . in one of the three persistent ( periodic ) -loud binaries , psr b1259 - 63 , the relativistic outflow is known to be produced by a young pulsar . in principle , a similar mechanism could power the activity of other sources ( except for cyg x-1 ) , although direct proof of the presence of the young pulsar in these systems is not possible : the radio emission from the compact object is free - free absorbed . recent puzzling detection of a short soft flare from one of the -loud binaries , lsi + 61 303 @xcite , may indicate the presence of a neutron star in the system . the outflows from lsi + 61 303 and ls 5039 , extending to the distances @xmath3 cm ( far beyond the binary orbit ) are revealed by the radio observations @xcite . the nature of the outflows ( a collimated jet or a wide - angle outflow ) is still debated . with the exception of cyg x-1 , all the known grlbs have similar spectral energy distributions ( sed ) , peaking in the mev - gev energy band . the physical mechanism producing the mev - gev bump in the spectra is , however , not clear . the emission from grlbs is supposed to come from internal and/or external shocks formed in the relativistic outflow either as a result of the development of intrinsic instabilities or through interactions with the stellar wind of the massive star . the mev - gev emission can be the synchrotron emission from electrons with energies much above tev @xcite , produced locally at the shock , or else , be produced via inverse compton scattering of the uv thermal emission from the massive star by electrons of the energies @xmath4 mev @xcite . the available multi - wavelength data do not constrain the composition of the relativistic wind from the compact object . on the one hand , the multi - tev or 10 mev electrons , responsible for the production of the mev - gev bump in the sed , could be injected into the shock region from the e@xmath1e@xmath2 pairs loaded wind . on the other , these electrons could be secondary particles produced in e.g. proton - proton collisions , if the relativistic wind is proton - loaded . the only direct way to test if relativistic protons are present in the emission region would be the detection of multi - tev neutrinos . the possibility of detection of neutrinos from grlbs by a km@xmath5-class neutrino telescopes was considered in several references @xcite . if the sources are assumed to be transparent to the tev s , the estimation of the neutrino flux is straightworward , given a known source flux and spectrum . the assumption of source transparency was adopted e.g. in the estimates of the number of detected neutrinos as in ref . however , the tev flux from the grlbs can be significantly attenuated by the pair production on the uv photon field of the massive star @xcite . in addition , if the s and neutrinos are produced close to the compact object , the flux can be further suppressed by pair production on the soft photons emitted by the accretion flow @xcite . the derivation of the estimate of the neutrino flux and spectral characteristics based on the observed tev emission is inconclusive due to the uncertain attenuation of the flux in the tev band ( see @xcite for s specific discussion of ) . in the absence of a direct relation between the characteristics of the observed tev and the neutrino emission from a grlb , the only way to constrain possible neutrino signals from the source is via the detailed modelling of the broad - band spectrum of the source within the hadronic model of activity . the idea is that the pp interactions , which result in the production of neutrinos , also result in the production of e@xmath1e@xmath2 pairs and the subsequent release of their energy via synchrotron , inverse compton and bremsstrahlung emission . the electromagnetic emission from the secondary e@xmath1e@xmath2 pairs is readily detectable . the total power released in the pp interactions determines the overall luminosity of the emission from the secondary pairs . the known electromagnetic luminosity and broad - band spectral characteristics of the source can be used to constrain the power released in pp interactions as well as the spectrum of the primary high energy protons . in the following we develop the hadronic model of activity of grlbs and derive the constraints on the spectrum and overall luminosity of neutrino emission from the analysis of the broad - band spectral characteristics of grlbs . although the following discussion is generically applicable for the grlbs as a class , we concentrate on the particular example of the system , because it is the only known persistent grlb in the northern hemisphere , available for observations with the icecube neutrino telescope @xcite . the existing observational data are found to be consistent with a possible very strong neutrino emission from ( with a flux at the level of @xmath6 erg/@xmath7s ) , close to the best reported amanda upper limit , @xmath8 ) @xcite ( a more recent reference @xcite combining more data reported a slightly degraded upper limit for over approximately the same range of energy , while the sensitivity had been improved by roughly a factor two ; this however translates a non significant but large background fluctuation at the source location ) . moreover , the assumption of an almost arbitrarily hard neutrino spectrum ( e.g. a powerlaw @xmath9 with index @xmath10 ) is not ruled out by the available multi - wavelength observational data . this means that , in principle , the soure could be readily detectable with icecube . the plan of the paper is as follows : in section [ sec : model ] we describe the general features of the hadronic model of activity of grlbs . in particular , we stress that when the massive companion star is a be type star , the presence of a dense equatorial decretion disk around the massive star can boost the pp interaction rate . at the same time , the emission from the pp interactions in the disk would be strongly suppressed , because of the large density of the soft photon background in the direct vicinity of the star . in section [ sec : numeric ] we perform the detailed numerical modeling of the broad - band spectra of grlbs in the hadronic model and show , on the particular example of , that the model provides a suitable explanation of the typical shape of the grlb seds . satisfactory fits to the observed seds can be achieved under quite arbitrary assumptions about the shape of the initial high energy proton spectrum . in particular , the initial spectra as different as an @xmath11 power law with a high energy cut - off and a monochromatic proton spectrum peaked at @xmath12pev energy could both explain the observed x - ray - to- spectrum of the source . finally , in section [ sec : icecube ] we work out the predictions for the detection of neutrinos from with icecube . we show that in an optimistic scenario , when the anisotropy of the neutrino emission of the source does not result in a suppression of the neutrino flux in the direction of the earth , should be detectable within a year of exposure . nevertheless , the spectral characteristics of the emission can only be marginally delineated after three years of exposure , given the wash out of the original neutrino spectrum from the measurement of the muon spectrum .

this is related to the fact that most neutrinos are produced in pp interactions close to the bright massive star , in a region optically thick for the tev s. considering the specific example of , we derive upper bounds for neutrino fluxes from various proton injection spectra compatible with the observed multi - wavelength spectrum . at this upper level of neutrino emission , we demonstrate that icecube will not only detect this source at c.l .

we present a hadronic model of activity for galactic -loud binaries , in which the multi - tev neutrino flux from the source can be much higher and/or harder than the detected tev flux . this is related to the fact that most neutrinos are produced in pp interactions close to the bright massive star , in a region optically thick for the tev s. considering the specific example of , we derive upper bounds for neutrino fluxes from various proton injection spectra compatible with the observed multi - wavelength spectrum . at this upper level of neutrino emission , we demonstrate that icecube will not only detect this source at c.l . after one year of operation , but , after 3 years of exposure , will also collect a sample marginally sufficient to constrain the spectral characteristics of the neutrino signal , directly related to the underlying source acceleration mechanisms .

1108.0429

i

understanding the nature and formation of cosmic dust is crucial to our understanding of the cosmos . over its 50-year history , infrared ( ir ) astronomy has shown that dust contributes to the physical processes inherent in star formation and mass - loss from evolved stars , as well as to several interstellar processes such as gas heating and the formation of molecules ( e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? in particular , silicate grains dominate dust emission in many astrophysical environments . the `` amorphous '' @xmath2 m and @xmath3 m silicate spectral features have been observed in almost every direction and to almost any distance , but the precise nature of this silicate dust remains a mystery . here we present a laboratory investigation of amorphous silicates , the type of dust grains most frequently inferred to exist from observational data . the classic `` 10@xmath0 m '' silicate feature was first observed in the late sixties in the ir spectra of several m - type giants and red supergiants ( rsgs ; * ? ? ? shortly thereafter a 10@xmath0 m absorption feature was discovered in the interstellar medium ( ism ; * ? ? ? * ; * ? ? ? since then , it has been found to be almost ubiquitous , occurring in many astrophysical environments including the solar system and extrasolar planetary systems ( e.g. , * ? ? ? * and references therein ) , the circumstellar regions of both young stellar objects and evolved intermediate mass stars ( asymptotic giant branch ; agb stars , and planetary nebulae ; e.g. , * ? ? ? * ; * ? ? ? * ) ; many lines of sight through the interstellar medium in our own galaxy ( e.g. , * ? ? ? * ) ; and in nearby and distant galaxies ( e.g. , * ? ? ? initially this feature was attributed to silicate minerals @xcite , based on mixtures of spectra of crystalline silicate species predicted to form by theoretical models @xcite . however , laboratory spectra of crystalline silicate minerals showed more structure within the feature than observed in the astronomical spectra ( see e.g. , * ? ? ? * ; * ? ? ? subsequent comparison with natural glasses ( obsidian and basaltic glass ; from e.g. , * ? ? ? * ) and with artificially disordered silicates @xcite showed that `` amorphous '' silicate was a better candidate for the 10@xmath0 m feature than any individual crystalline silicate mineral . since then , it has been commonly assumed that description of silicate as disordered or `` amorphous '' is synonymous with glassy silicate . however , this is an oversimplification . the term `` glass '' has a specific definition , i.e. the solid has no long - range order beyond nearest - neighbor atoms . `` crystalline '' is often taken to mean single crystals , but it is possible to form poly - nanocrystalline agglomerates , with a continuum which essentially extends from a true glass to a single crystal grain . furthermore , natural and synthetic `` glasses '' often contain microlites in addition , one might expect agglomerated particles to be polymineralic , and possibly to contain both crystalline and glassy constituents . @xcite introduced the idea of `` chaotic silicate '' in which the level of disorder is even greater than for glass . a chaotic silicate does not have to be stoichiometric , can contain different compositional zones within a single grain , and may be porous , and therefore much lower density than a glass . this range of possible grain types is demonstrated schematically in fig . [ fig : xtalc ] . in astrophysical environments , whether a solid is glassy , crystalline or some combination of the two has implications for its formation , and subsequent processing , evolution and destruction , and thus it is important to have tools to distinguish between such grain types . for example , true glasses with no inclusions will not transform into crystals below their glass transition temperature ( @xmath4 ; see [ silglass ] ) , whereas a glass already containing microlites can continue to crystallize at slightly lower temperatures . in the case of terrestrial obsidians , with 900k @xmath5 1000k , elemental diffusion profiles suggest that crystal growth can continue down to @xmath1700k ( e.g. , * ? ? ? * ) . if poly - nano - crystalline grains can be distinguished spectroscopically in the lab from truly glassy grains , we can test for their presence in astrophysical environments . for instance @xcite showed that there is a difference between single crystal and polynanocrystalline silicon carbide ( sic ) , while @xcite showed that glassy sic looks different than various crystalline samples . these laboratory data were invoked to explain changes in sic grains formed as carbon stars evolve . for silicates , laboratory data on poly - nano - crystalline samples are lacking . whether grains are glassy or poly - nano - crystalline is an indicator of whether grains form or are processed above @xmath4 . if the two forms can not be distinguished in laboratory spectra , then the `` amorphous '' nature of silicates in space would no longer necessarily imply a truly glassy structure , allowing the possibility of higher dust formation temperatures . many observations have shown that the 10@xmath0 m silicate feature varies from object to object and even within a single object both temporally ( e.g. , * ? ? ? * ) and spatially ( e.g. in @xmath6 car , n. smith , pers . comm ) . within a single type of astrophysical object , the feature shows huge variations in terms of its peak position , width and its ratio to the @xmath7 m feature ( e.g. * ? ? ? * ; * ? ? ? variations in feature shape from star to star can not be explained in terms of optical depth or grain temperature effects . several interpretations of these observations have been suggested including : grain size effect ( e.g. , * ? ? ? * ) ; mg / fe ratio and ( mg+fe)/si ratio ( e.g. * ? ? ? * ) ; inclusion of oxide grains ( e.g. , * ? ? ? * ) ; increasing crystallinity ( e.g. , * ? ? ? * ; * ? ? ? * ) ; grain shape ( e.g. , * ? ? ? * ) ; and grain porosity ( e.g. , * ? ? ? * ; * ? ? ? however , all models of these effects utilize laboratory spectra , and are only as reliable as the data that goes into them . the near ubiquity of `` amorphous '' silicate features and their variations in strength , width , peak position and the ratio of the 10@xmath0m/18@xmath0 m features potentially provide the diagnostic tools to understand the detailed mechanisms by which dust is formed , processed and destroyed . however , existing laboratory and synthetic spectra are not sufficiently well understood to achieve this goal . since the discovery of the 10@xmath0 m feature , there have been many laboratory studies producing ir spectra and optical functions of various samples for comparison with and modeling of observational data . in addition , synthetic optical functions have been derived from observational spectra , often combined with laboratory mineral data , in order to match the observed features ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? the first laboratory spectra used in astronomical silicate studies were of crystalline silicates and natural glasses ( obsidian and basaltic glass , which contain some microlites ; e.g. , * ? ? ? various studies produced `` amorphous '' samples through chemical vapor deposition ( e.g. , * ? ? ? * ) , smokes ( e.g. , * ? ? ? * ) , ion - irradiation of crystalline samples ( e.g. , * ? ? ? * ) , laser ablation of crystalline samples @xcite , and quenching melts to glass ( e.g. , * ? ? ? * ; * ? ? ? however , these techniques yield different results . for instance the peak positions , full width at half maxima ( fhwma ) and ratios of the strengths of the 10 and 18@xmath0 m features vary between datasets even though the materials investigated are ostenibly the same composition . spectra from samples with the same reported composition vary , which should not occur if the samples had the same structures , and if all spectra were obtained under optically thin conditions . a detailed comparison between existing and new laboratory data are given in [ comparison ] . the sample preparation techniques vary widely and lead to a range of disordered structures . unfortunately we do not have sufficient information on the physical structure or chemical characteristics of previously studied samples to determine the effects quantitively , but a qualitative analysis presented here highlights the need to make such sample information available . the data used most commonly for modeling astronomical environments are synthetic optical functions such as ( * ? ? ? * hereafter dl ) and ( * ? ? ? * hereafter ohm ) . these data are favored over laboratory spectra because they have broad wavelength coverage , which is not true of individual laboratory datasets . however , these synthetic functions were produced using compilations of laboratory spectral data and astronomical observed dust opacities from which new optical functions were calculated . the derived optical functions were then modified specifically to match the astronomical observations . for instance , in the @xcite data , the 9.7@xmath0 m feature is entirely derived from observational opacities , while the nir - nuv section of their optical function uses laboratory data from crystalline olivine studies , and the fuv / x - ray region uses laboratory data for crystalline alumina ( al@xmath8o@xmath9 ) . both @xcite and @xcite blend laboratory and astronomical data and their optical functions will match some spectral features , and can be used for comparison of optical depths between different dusty environments . however , they do not represent real solids and thus can not be used to determine the true nature of dust in space , how it varies spatially or temporally , or why . the basic building block of silicates is the sio@xmath10 tetrahedron . these can be linked in a framework , with each oxygen shared between two tetrahedra ( e.g. sio@xmath8 minerals and feldspars ) , or they can be linked in chains ( e.g. pyroxenes such as diopside [ di ; camgsi@xmath8o@xmath11 , enstatite [ en;mgsio@xmath9 ] ) or they can be isolated tetrahedra ( e.g. the olivines series : forsterite [ fo ; mg@xmath8sio@xmath13 to fayalite [ fa ; fe@xmath8sio@xmath13 ) . in all cases , the non - shared oxygens ( known as non - bridging oxygens or nbos ) are charge - balanced by other cations ( e.g. mg@xmath14 , fe@xmath14 , ca@xmath14 , na@xmath15 , etc ) . the ca - mg - al silicates that are expected to form in circumstellar environments are dominantly of pyroxene and olivine composition . within each mineral group , solid solution allows compositions to vary between end - members . in the case of similarly - sized cations the solution may be continuous e.g. , enstatite to ferrosilite ( fs ; fesio@xmath9 ) and the olivine series . given the availability of other cations , end - member pyroxenes rarely occur in terrestrial or meteoritic samples . where the substituting cation is a different size , solid solution is more limited , for example between enstatite and diopside . in such cases , solid solution becomes less extensive at lower temperatures , so that cooling may lead to `` exsolution '' of two different pyroxene compositions from an initially homogeneous high - temperature solid . minerals occur as crystals that possess long - range order , with very narrow distributions of bond angles and lengths . this leads both to anisotropy ( properties varying with crystal orientation ) and narrow spectral features . silicate glasses are the `` frozen '' structural equivalents of liquids , possessing short - range order ( so that local charge - balance is conserved for example ) but lacking the long - range order that gives rise to symmetry and anisotropy in crystals . glasses are therefore both isotropic and have broad spectral features . the basic structural unit of silicate glasses and melts is the sio@xmath10 tetrahedron , as is the case in crystalline silicate minerals . oxygens linking tetrahedra are known as bridging oxygens ( bo ) , while non - bridging oxygens ( nbo ) are coordinated by metal cations , which are termed network - modifiers in this role . tetrahedral cations ( t ) include not only si@xmath16 , but also trivalent cations such as al@xmath17 and fe@xmath17 ; these must be charge - balanced by other cations ( usually alkalis or alkaline earths ; fig . [ cartoon ] ) . the degree of polymerization of a melt or glass can be summarized by the ratio of nbo / t , which can range from 0 ( fully polymerized , e.g. sio@xmath8 ) to 4 ( fully depolymerized , e.g. mg@xmath8sio@xmath18 ) . in general , more polymerized melts are more viscous and have higher glass transition temperatures . on quenching a melt , its structure is `` frozen in '' at the glass transition if cooling is rapid enough to prevent crystallization . the glass transition is actually an interval , often approximated by the glass transition temperature ( @xmath4 ) which is usually taken to be the temperature at which the viscosity is 10@xmath19 pa.s ( @xmath20 ) . rapid cooling from a given temperature preserves the network present in the liquid at that particular temperature . because of this behavior , glasses of any given composition can have subtle differences in structure that depend on cooling rates . the temperature at which the glass has the same structure as the melt is called the fictive temperature ( @xmath21 ) . see @xcite for a comprehensive review of melt structure and properties . two issues whose importance will be discussed in the current work are the role of water and the oxidation state of iron . at low water contents ( less than about 1 wt.% total h@xmath8o ) , water dissolves in silicate glasses almost exclusively as hydroxyl ( oh@xmath22 ) ions @xcite , and acts as a network modifier ( fig . [ cartoon ] ) . compared to other modifier oxides such as na@xmath8o and mgo , water has a more dramatic effect in reducing melt viscosity and glass transition temperatures @xcite . iron can play the role of network modifier ( octahedral fe@xmath14 or fe@xmath17 ) or network - forming cation ( tetrahedral fe@xmath17 ) . consequently , the oxidation state of an iron - bearing glass or melt has a significant effect on its structure and properties . from the perspective of cosmic dust formation , the glass transition temperature is essentially the temperature above which a given composition should form as or convert to crystalline solids , whereas solids formed below this temperature will be glassy if they cool sufficiently rapidly @xcite . more depolymerized melts are more difficult to quench , and melts less polymerized than pyroxenes ( nbo / t @xmath23 2 ) typically require extreme quench rates ( 100s ks@xmath24 ) using methods such as containerless laser processing to achieve truly glassy samples @xcite . for a given composition , faster cooling rates result in a higher t@xmath25 . this dependence can be determined by differential scanning calorimetry using different heating and cooling rates , and is used to determine the cooling rate of natural lava samples @xcite . for depolymerized silicates ( e.g. olivines and pyroxenes ) , if glassy grains form they must do so below their @xmath4 because the cooling rate required for quenching to a glass is extremely rapid . highly polymerized silicates ( e.g. silica , obsidian ) can be cooled more slowly , over hours or days , and not crystallize @xcite . however , the cooling timescales ( months ) determined by @xcite for agb star circumstellar shells are sufficiently long as to preclude the preservation of glassy / chaotic solids that form above @xmath4 , because annealing timescales are shorter than those for cooling for all but the most polymerized silicates . modeling of silicate dust in space has been limited by the available laboratory data the influence of various model parameters was investigated by @xcite , who found that using so - called `` clean '' ( i.e. pure magnesium ) silicate grains to model the observed 9.7@xmath0 m features did not yield a good fit due to the lack of absorption by these grains in the visible and near - ir . they also found that just mixing in more absorbing grains did not solve the problem . this led to the suggestion that the grains responsible for the 9.7@xmath0 m feature are `` dirty '' silicates , i.e. mg - silicates with impurities introduced into the matrix giving more opacity in the optical and near - ir . it is known that nbo / t ( polymerization ) affects the spectra of amorphous silicates such that the peak position of the 10@xmath0 m feature shifts redwards as nbo / t increases ( e.g. @xcite ) . aluminium ( al ) is a network former and consequently al content strongly affects nbo / t . @xcite suggested that al may be an important component of silicates in space that could explain why previous laboratory spectroscopic studies failed to match observational data . other cations may be equally important . ca@xmath14 and fe@xmath14 both substitute for mg , while fe@xmath17 will substitute for tetrahedral site ( e.g. si@xmath26 or al@xmath17 ) . therefore , the oxidation state is another important variable in addition to elemental substitutions . existing laboratory spectral data for `` amorphous '' silicates were produced using samples that are not sufficiently well - characterized to allow astronomers to interpret their observations without ambiguity . here we present new laboratory spectra of several silicate glasses of astronomical relevance , and discuss compositional factors that influence their spectral features . we compare these new data with those previously available for `` amorphous '' silicates and discuss how these samples compare to successfully - applied synthetic optical functions . we find that the synthetic spectra can not be well matched by the conventionally assumed glassy silicate composition and discuss whether astrophysical silicates need to be truly glassy .

we present a laboratory study of silicate glasses of astrophysically relevant compositions including olivines , pyroxenes and melilites . with emphasis on the classic si o stretching feature near 10 m , we compare infrared spectra of our new samples with laboratory spectra on ostensibly similar compositions , and also with synthetic silicate spectral data commonly used in dust modeling . the convolution of chemical and physical effects makes it difficult to attribute changes in spectral parameters to any given variable .

we present a laboratory study of silicate glasses of astrophysically relevant compositions including olivines , pyroxenes and melilites . with emphasis on the classic si o stretching feature near 10 m , we compare infrared spectra of our new samples with laboratory spectra on ostensibly similar compositions , and also with synthetic silicate spectral data commonly used in dust modeling . several different factors affect spectral features including sample chemistry ( e.g. , polymerization , mg / fe ratio , oxidation state and al - content ) and different sample preparation techniques lead to variations in porosity , density and water content . the convolution of chemical and physical effects makes it difficult to attribute changes in spectral parameters to any given variable . it is important that detailed chemical and structural characterization be provided along with laboratory spectra . in addition to composition and density , we measured the glass transition temperatures for the samples which place upper limits on the formation / processing temperatures of these solids in space . popular synthetically - generated optical functions do not have spectral features that match any of our glass samples . however , the m feature generated by the synthetic data rarely exactly matches the shape and peak position of astronomically observed silicate features . our comparison with the synthetic spectra allows astronomers to determine likely candidates amongst our glass samples for matching astronomical observations .

astro-ph0504313

i

the determination of the stellar content of unresolved systems from observations of their integrated light is a fundamental challenge to extragalactic astronomers . the problem has been traditionally approached by comparing the integrated properties ( spectral energy distributions , line strengths , colors ) of remote systems with those of better - understood local templates ( e.g. faber 1973 , burstein 1984 , rose 1985 ) . more recently , stellar population synthesis ( sps ) models combined with our knowledge of the stellar evolution of stars and of the behaviour of their emitted light as a function of fundamental stellar parameters have been constructed to predict integrated properties of single and composite stellar populations in integrated light ( e.g. le borgne 2004 , bruzual & charlot 2003 , thomas , maraston & bender 2003 , vazdekis 1999 , worthey 1994 ) . in this context , the galactic globular cluster ( gc ) system plays a crucial role . it consists of a set of increasingly well studied stellar populations which are close enough that their constituent stars can be resolved and studied individually and meaningful color - magnitude diagrams can be constructed , and yet their compact structures enable observations of their integrated light relatively easily . integrated observations of gcs can be used to construct calibrations of integrated observables as a function of the parameters that characterize stellar populations ( mainly age , metallicity , and abundance pattern ) . such calibrations provide useful , fairly model - independent tools for the conversion of integrated observables of distant systems into fundamental stellar population parameters . moreover , comparisons of sps models with integrated observations of galactic gcs has become commonplace ( e.g. proctor , forbes & beasley 2004 , schiavon 2004a , b , maraston 2003 , puzia 2002 , schiavon 2002a , b , beasley , hoyle & sharples 2002 , vazdekis 2001 , gibson 1999 , schiavon & barbuy 1999 , bruzual 1997 , rose 1994 , and references therein ) . such fundamental comparisons aim primarily at verifying the validity of the models , whose predictions must match the integrated properties of gcs for the known set of input stellar population parameters . reliable databases of integrated properties of galactic gcs are therefore precious resources and numerous efforts have been invested towards their collection in the past . notable among these are the works of puzia ( 2002 ) , cohen , blakeslee & ryzhov ( 1998 ) , covino , galletti & pasinetti ( 1995 ) , bica & alloin ( 1986 ) , burstein ( 1984 ) , and zinn & west ( 1984 ) , where integrated spectra of moderate to large - sized samples of galactic gcs were collected . in spite of these and other previous works , there remains considerable room for improvement to the available spectroscopic databases which are deficient in one or more of such crucial features as size , a representative range of metallicities and horizontal branch ( hb ) morphologies , signal - to - noise ratio ( s / n ) , resolution , and homogeneity . these features are all essential both for a robust calibration of stellar population synthesis models and for the direct comparison with observations of distant systems . this work aims at providing this much needed improvement . we present new , high - s / n , moderately high - resolution , integrated spectra of 40 galactic globular clusters obtained with the same instrumental setup and over a single observing run . this is the largest collection of optical integrated spectra of galactic gcs to date with such high s / n and resolution , and should serve as a prime database for comparison with observations of remote stellar systems and the calibration of sps models . this paper focuses on the detailed description of our observations and data reduction procedures , and the presentation of the final data products . a first exploration of this spectral library , focussed on the effects of hb morphology on different balmer lines , was presented in schiavon ( 2004b ) . the paper is organized as follows : we describe the sample selection and observations , in sections [ sec : sselection ] and [ sec : obsdata ] , respectively , and the reductions are discussed in section [ sec : reductions ] . the final spectra are presented in section [ sec : spectra ] and section [ sec : notes ] contains notes on individual clusters . our results are summarized in section [ sec : summary ] .

we present a new library of integrated spectra of 40 galactic globular clusters , obtained with the blanco 4-m telescope and the r - c spectrograph at the _ cerro tololo interamerican observatory_. the spectra cover the range 3350 6430 with 3.1 ( fwhm ) resolution . the selected targets span a wide range of cluster parameters , including metallicity , horizontal - branch morphology , galactic coordinates , galactocentric distance , and concentration . the total sample is thus fairly representative of the entire galactic globular cluster population and should be valuable for comparison with similar integrated spectra of unresolved stellar populations in remote systems . for most of the library clusters , we present a detailed account of the observations and data reduction .

we present a new library of integrated spectra of 40 galactic globular clusters , obtained with the blanco 4-m telescope and the r - c spectrograph at the _ cerro tololo interamerican observatory_. the spectra cover the range 3350 6430 with 3.1 ( fwhm ) resolution . the spectroscopic observations and data reduction were designed to integrate the full projected area within the cluster core radii in order to properly sample the light from stars in all relevant evolutionary stages . the s / n values of the flux - calibrated spectra range from 50 to 240/ at 4000 and from 125 to 500/ at 5000 . the selected targets span a wide range of cluster parameters , including metallicity , horizontal - branch morphology , galactic coordinates , galactocentric distance , and concentration . the total sample is thus fairly representative of the entire galactic globular cluster population and should be valuable for comparison with similar integrated spectra of unresolved stellar populations in remote systems . for most of the library clusters , our spectra can be coupled with deep color - magnitude diagrams and reliable metal abundances from the literature to enable the calibration of stellar population synthesis models . in this paper we present a detailed account of the observations and data reduction . the spectral library is publicly available in electronic format from the national optical astronomical observatory website .

0711.1617

i

eclipsing binary stars ( ebs ) are important for astrophysical research in many ways . they may be used to obtain accurate estimates of star masses and radii ( * ? ? ? * and references therein ) . precise determination of stellar parameters can in turn be used to put theories of stellar structure and evolution to a stringent test by comparing measured parameters with theoretical predictions ( * ? ? ? * ; * ? ? ? * and references therein ) . ebs may also be used for distance determination and this use goes back several decades ; its history is reviewed by @xcite . since @xcite used an estimate of the parallax to @xmath2 aurig to infer the surface brightness of both its components , it has been known that a good photometric light curve plus a double line spectroscopic orbit admits a simple geometric relationship between the surface brightnesses of the stars and the distance to the eb ; @xcite however had no way at the time to make the reverse `` surface brightness to distance '' inference and his paper does no mention this possibility . after @xcite , other early papers @xcite used parallaxes obtained independently to estimate surface brightnesses , but , as remarked by @xcite , these pioneers surely knew of the potential of this technique to estimate distances . modern analyses of ebs have usually focussed on this technique ( e.g. @xcite ) . the method affords high precision due to its purely geometrical nature and has been applied by a number of authors to determine the distance to the large magellanic cloud ( lmc ) using hv2274 @xcite , hv982 @xcite , eros 1044 @xcite and hv 5936 @xcite ; an attempt to use ebs to determine the distance to m31 is currently under way @xcite and the direct project is attempting to measure the distance to m31 and m33 via ebs and cepheids @xcite ; other recent examples include @xcite who present a sample of detached binaries in the lmc for distance determination and @xcite who present the first determination of the distance and properties of an eb in m31 ; @xcite presents a sample of ebs with total eclipses in the lmc suitable for spectroscopic studies . in general it is important that distances be determined using a large sample of ebs to minimize the impact of systematic errors . a recent collection of references on extragalactic binaries can be found in @xcite . large - scale surveys to detect gravitational microlensing events have identified and collected light curves for large numbers of variable stars in the bulge of the milky way and in the magellanic clouds . eclipsing binary stars comprise a significant fraction of these collections . the macho collaboration has presented a sample of 611 ebs in the lmc with preliminary analyses of their orbits @xcite . a catalogue of @xmath3 ebs in the lmc found in the macho database has been just published by @xcite ; this catalogue was compiled by analyzing a list of @xmath4 stars classified as possible ebs in the macho database ; a cross correlation between these @xmath4 stars and our sample finds just @xmath5 matches , thus at least about @xmath6 ebs in our catalogue are new identifications . the @xmath4 classified as possible ebs were found in regions of parameter space such as color , magnitude , and period , where one does not expect to find pulsating variables and therefore the detected variability of these stars was _ tentatively _ ascribed to eclipses . regions where pulsating variables could exist were not considered while making this preliminary classification and ebs there were therefore not included in the list . in our search we did not rely primarily on cuts in parameter space and and we did not exclude a priori regions of this space where pulsating variables are present ; therefore we were able to classify many ebs in these regions , that were not included in the preliminary classification . the ogle collaboration ] has introduced a sample of @xmath7 ebs in the lmc @xcite and of @xmath8 ebs in the small magellanic cloud ( smc : * ? ? ? * ) . both samples were selected from their catalogue of variable stars in the magellanic clouds @xcite compiled from observations taken during the second part of the project ( ogle ii : * ? ? ? * ) and reduced via difference image analysis ( dia : * ? ? ? * ) . an earlier sample of @xmath9 ebs in the bar of the lmc was presented by the eros collaboration@xcite . other large variable star data sets are being produced by surveys not specifically designed to detect gravitational microlensing , such as the all sky automated survey ( asas : * ? ? ? ] the availability of large samples of ebs ( and the even larger ones that can be found by future surveys such as pan - starrs and lsst ) can have an important impact on stellar astrophysics . this impact can arise in two qualitatively different approaches . first , a large catalogue allows the discerning researcher to select carefully a few ebs for detailed follow - up study ; the distance estimation described above is an example of this . second , statistical analyses of an entire population become possible when a large collection is assembled ; such analyses of ebs have not previously been possible . to fulfill this promise there are challenges to overcome , including finding ebs in large data sets and automating their analysis . with regard to the first task , the _ discovery _ problem is complicated by the fact that ebs do not have clear relationships between their parameters ( period , luminosity , colors ) as do the major classes of pulsating variables . this makes it difficult to find them via simple and well understood cuts in parameter space . the first step toward automated discovery is thus to have a large sample of data on which to experiment with search techniques . this non - trivial exercise in mining large data sets can be useful for future surveys that are not necessarily aimed at binary star research . an example is given by @xcite and @xcite who employ an artificial neural network to identify ebs in the ogle - ii lmc and smc samples , but more needs to be done . with regard to _ analysis _ of ebs , the traditional approach has been to carefully analyze individual systems with the help of dedicated computer codes such as the wilson - devinney code ( wd : * ? ? ? * ; * ? ? ? this becomes impracticable when many thousands of stars are involved and an automated approach is required . the light curves in a previous sample of 1459 ebs in the smc found by ogle - ii @xcite were systematically solved by @xcite using an automated version of the wd code ; the asas collaboration has developed an automated classification algorithm for variable stars based on fourier decomposition @xcite ; @xcite found and analyzed 10000 bulge ebs from ogle - ii using debil ] , an eb analysis code that allows automated solutions of large eb data sets and works best for detached ebs ; a genetic algorithm based approach to finding good initial parameters for wd is described in @xcite . this paper is the first of a series of papers aimed at describing the eb samples in the macho database and is organized as follows : section [ sec : sample ] introduces the lmc and smc samples ; section [ sec : diagrams ] describes the color magnitude diagram ( cmd ) and the color period diagram , pointing out significant features in them , section [ sec : comparison ] compares the lmc and smc samples , section [ sec : crossogle ] describes the results of the cross correlation with the ogle lmc and smc samples , and section [ sec : online ] reports where and in what form the data presented in the paper can be accessed on line .

we present a new sample of eclipsing binary stars in the large magellanic cloud ( lmc ) , expanding on a previous sample of 611 objects and a new sample of eclipsing binary stars in the small magellanic cloud ( smc ) , that were identified in the light curve database of the macho project . we perform a cross correlation with the ogle - ii lmc sample , finding 1236 matches . a cross correlation with the ogle - ii smc sample finds 698 matches .

we present a new sample of eclipsing binary stars in the large magellanic cloud ( lmc ) , expanding on a previous sample of 611 objects and a new sample of eclipsing binary stars in the small magellanic cloud ( smc ) , that were identified in the light curve database of the macho project . we perform a cross correlation with the ogle - ii lmc sample , finding 1236 matches . a cross correlation with the ogle - ii smc sample finds 698 matches . we then compare the lmc subsamples corresponding to center and the periphery of the lmc and find only minor differences between the two populations . these samples are sufficiently large and complete that statistical studies of the binary star populations are possible .

1610.09159

i

hall magnetohydrodynamics ( hmhd hereafter ) provides a natural extension of ideal or resistive magnetohydrodynamic ( mhd ) models for plasmas in the limit of small scales , where the magnetic field is frozen into electron fluid but ions are decoupled from the magnetic field lines @xcite . as related to different masses of ions and electrons , the inertial effects become important at scales of the order of the ion inertial length ( sometimes referred to as the ion skin depth ) @xmath0 , where @xmath1 is the alfven speed and @xmath2 is the ion gyrofrequency . the hmhd physics is essentially contained in the ohm s law modified in comparison with the mhd formulation , which influences the transport of the magnetic field in plasma through the faraday s induction equation . the hall term also enters the energy conservation equation . dispersive effects related to the hall term are responsible for the appearance of so - called whistler waves . hmhd - related phenomena are studied as an important element of fast magnetic reconnection @xcite . the hmhd physics includes also processes of formation of solitary waves @xcite . the hall term is also important for modeling small - scale fluctuations in plasma turbulence @xcite . in collisionless or weakly collisional plasmas one may expect the development of thermal pressure anisotropies . lack of collisional mechanisms of exchange of particle energy between degrees of freedom parallel and perpendicular to the magnetic field direction may obviously lead to an asymmetric distribution function for particle velocities . in the lowest - order approximation , a gyrotropic model of anisotropy applies , where the distribution function is assumed to be bi - maxwellian and axially symmetric with respect to the local magnetic field direction . in this approach , the parallel and perpendicular temperatures are in general different and they evolve in time in a different way . the pressure anisotropy is known to provide free energy for the development of instabilities , that are believed to control the pressure anisotropy in space plasmas as measured in - situ in the solar wind @xcite . questions related to the pressure anisotropy regulation in space plasmas have been investigated extensively in various astrophysical aspects @xcite . there exist a number of numerical codes for numerical simulations within the hmhd framework . the codes use explicit time advancing ( e.g. @xcite ) or implicit scheme ( e.g. @xcite ) . efforts have been made towards including adaptive mesh refinement in hmhd simulations @xcite . however , quantitative validation of hmhd codes in nonlinear regime is difficult due to the lack of analytic or semi - analytic problems that could be used for this purpose . quantitative testing of the accuracy of hmhd codes consists mainly in studying of propagation of small - amplitude whistler waves in the computational domain . to our knowledge , no general method of testing of absolute accuracy has been proposed for the nonlinear regime of hmhd dynamics . in this paper , we discuss a method of solving of the hmhd equations with the isotropic or anisotropic thermal pressure . the algorithm can be briefly described as using the second - order runge - kutta advancing in time and kurganov - tadmor scheme with van leer flux limiter for the approximation of fluxes . to preserve solenoidal magnetic field during time evolution , the magnetic field transport equation is advanced in time using so - called flux - interpolated constrained - transport approach . the pressure tensor can be modeled in a gyrotropic approximation with polytropic relations describing the evolution of the parallel and perpendicular pressures . it is also possible to use an equation for the evolution of the perpendicular pressure and the explicit energy conservation equation , which guarantees the conservation of the total energy averaged over the simulation box to a very high accuracy . for isotropic pressure case also a polytropic state equation or the explicit energy conservation equation can be used . the presented scheme is intended for simulations of phenomena in the range of scales of the order of the ion inertial length and larger . this range of scales is determined by a general physical regime of validity of the hmhd equations , but also by the explicit character of the proposed numerical scheme that imposes strong constraints on the simulation time step . the algorithm is shown to work properly for one- , two- and three - dimensional test problems of different types : solitary waves propagation , magnetic reconnection , and the growth of the firehose instability . in this paper , we also discuss thoroughly a new testing method based on the propagation of solitary structures as a possible testing framework for hmhd in the nonlinear regime .

we present a numerical solver for plasma dynamics simulations in hall magnetohydrodynamic ( hmhd ) approximation in one , two and three dimensions . we consider both isotropic and anisotropic thermal pressure cases , where a general gyrotropic approximation is used . the numerical scheme incorporates second - order runge - kutta advancing in time and kurganov - tadmor scheme with van leer flux limiter for the approximation of fluxes . hall magnetohydrodynamics , numerical methods , solitary waves , anisotropic pressure

we present a numerical solver for plasma dynamics simulations in hall magnetohydrodynamic ( hmhd ) approximation in one , two and three dimensions . we consider both isotropic and anisotropic thermal pressure cases , where a general gyrotropic approximation is used . both explicit energy conservation equation and general polytropic state equations are considered . the numerical scheme incorporates second - order runge - kutta advancing in time and kurganov - tadmor scheme with van leer flux limiter for the approximation of fluxes . a flux - interpolated constrained - transport approach is used to preserve solenoidal magnetic field in the simulations . the implemented code is validated using several test problems previously described in the literature . additionally , we propose a new validation method for hmhd codes based on solitary waves that provides a possibility of quantitative rigorous testing in nonlinear ( large amplitude ) regime as an extension to standard tests using small - amplitude whistler waves . quantitative tests of accuracy and performance of the implemented code show the fidelity of the proposed approach . hall magnetohydrodynamics , numerical methods , solitary waves , anisotropic pressure

1610.09159

i

we present a second - order accurate solver for the hmhd equations with anisotropic or isotropic thermal pressure . both explicit energy conservation equation and polytropic state equations can be used in this approach as the closure for the hmhd model . the implemented code was validated using test problems previously described in the literature : the magnetic reconnection process and the growth of the firehose instability . additionally , we propose a new validation method for the hmhd codes based on solitary waves that provides a possibility of quantitative testing in nonlinear regime as a complementary approach to standard tests using small - amplitude whistler waves . quantitative tests of the accuracy and the performance of the implemented code show the fidelity of the proposed approach . it is demonstrated that the efficiency of the proposed approach and its implementation are sufficient for three - dimensional simulations within the hmhd framework . the present formulation of the numerical scheme for the hmhd equations is purely explicit and can be accelerated by using , e.g. a subcycling procedure for the integration of the equation for the magnetic field transport as proposed in ref . another possibility of acceleration of the computations includes applying an implicit scheme , where stability of the code is not constrained by the cfl condition for whistler waves at the expense of the accuracy of the computations . in these contexts the proposed method of validation based on solitary waves can be particularly useful for testing the accuracy of the modified approaches . since in some aspects the hmhd model can be considered as a low - beta approximation for kinetic models , the testing method based on solitary waves presented in this paper has also conceivable applications for testing / validation of kinetic ( particle - in - cell or vlasov - maxwell ) models .

both explicit energy conservation equation and general polytropic state equations are considered . the implemented code is validated using several test problems previously described in the literature . additionally , we propose a new validation method for hmhd codes based on solitary waves that provides a possibility of quantitative rigorous testing in nonlinear ( large amplitude ) regime as an extension to standard tests using small - amplitude whistler waves . quantitative tests of accuracy and performance of the implemented code show the fidelity of the proposed approach .

we present a numerical solver for plasma dynamics simulations in hall magnetohydrodynamic ( hmhd ) approximation in one , two and three dimensions . we consider both isotropic and anisotropic thermal pressure cases , where a general gyrotropic approximation is used . both explicit energy conservation equation and general polytropic state equations are considered . the numerical scheme incorporates second - order runge - kutta advancing in time and kurganov - tadmor scheme with van leer flux limiter for the approximation of fluxes . a flux - interpolated constrained - transport approach is used to preserve solenoidal magnetic field in the simulations . the implemented code is validated using several test problems previously described in the literature . additionally , we propose a new validation method for hmhd codes based on solitary waves that provides a possibility of quantitative rigorous testing in nonlinear ( large amplitude ) regime as an extension to standard tests using small - amplitude whistler waves . quantitative tests of accuracy and performance of the implemented code show the fidelity of the proposed approach . hall magnetohydrodynamics , numerical methods , solitary waves , anisotropic pressure

1201.1290

i

the ionizing continuum of stars at @xmath4 is of major importance for interpreting emission line observations of galaxies because many of the strong lines observed in the spectra of galaxies , such as @xmath5\:\lambda5007}$ ] , @xmath6\:\lambda3869}$ ] and @xmath0 , have ionization potentials in excess of 13.6 ev . despite this importance we are severely limited by interstellar absorption in observing stellar spectra in this spectral window directly ( e.g. * ? ? ? although we can get direct information at slightly longer wavelengths with space - based uv spectroscopy ( e.g. * ? ? ? * ) , most of our knowledge about the @xmath7 region is based on indirect evidence , even for solar metallicity . a promising way to indirectly obtain information on the stellar ionizing continuum is to compare emission line properties ( e.g. flux , equivalent width ) to predictions from photoionization codes such as cloudy @xcite or mappings iii @xcite . in practice these kinds of studies provide modest constraints on stellar atmosphere models ( e.g. * ? ? ? . however where predictions of models differ significantly , this approach can yield useful information . this is the approach we will adopt in this work , where we will make use of the @xmath0 nebular emission line to place constraints on stellar models and in particular on the ionization mechanism for this line . the presence of a nebular @xmath0 line in the integrated spectrum of a galaxy indicates the existence of sources of hard ionizing radiation as the ionization energy for he@xmath8 is 54.4 ev ( @xmath9 ) . this hard radiation can of course be produced by an active galactic nucleus ( agn ) , and most sources with luminous @xmath10ii emission , in a flux limited sample , are indeed galaxies with an agn . however the required hard radiation can also be provided by stellar sources and @xmath0 emission is frequently seen in @xmath11ii - galaxies . the line appears to be associated with young stellar populations ; for instance , @xcite proposed o__f _ _ stars as the sources of @xmath0 emission in dwarf galaxies . subsequent discussion has mostly focused on wolf - rayet ( wr ) stars , although the distinction between these two classes is rather blurred ( e.g. * ? ? ? * ) . * see also @xcite ) showed that the hard radiation field of wr stars could provide a good explanation of the nebular @xmath12 seen in @xmath11ii - galaxies . @xcite tried to test this in a careful study of @xmath11ii - galaxies with prominent wr features . they were however unable to find wr features in 12 out of the 30 galaxies with nebular @xmath13 emission . the same lack of wr features in metal poor blue compact dwarf ( bcd ) galaxies was pointed out by @xcite . they proposed that fast radiative shocks could be responsible for this emission ( see also @xcite ) . similar results were reported by ( * ? ? ? * hereafter b08 ) , who analysed a sample of strong emission line galaxies in the sloan digital sky survey @xcite with @xmath0 emission . they showed that at least at metallicities of @xmath14 , there appeared to be a close correlation between wr features in galaxies and the presence of @xmath15 emission , but this appeared not to be so clear - cut at lower metallicities . this apparent lack of connection of @xmath10ii emission with the hard uv radiation from wr stars has also been seen in spatially resolved spectroscopic studies . @xcite performed an integral field spectroscopy study for the @xmath11ii galaxy iizw70 and found that the region associated with nebular @xmath0 emission was a few arcsec offset from the region with detected wr features . more recently @xcite and @xcite have presented studies of @xmath15 emission in m33 . both studies find some regions with nebular @xmath15 emission that are not associated with wr stars ( see also @xcite , @xcite and @xcite ) . thus a series of studies have shown that while @xmath0 emission frequently is found in association with wr stars , it appears not to be so in all cases , particularly at low metallicity . as mentioned above , possible additional sources of high energy photons could be x - ray binaries @xcite , strong shocks @xcite , low - level agn activity and alternative models for stellar evolution @xcite . however the existing studies do not show clear trends that allow us to distinguish between these scenarios . crucially the samples in most of the previous studies have not been selected specifically to study @xmath10ii emission lines . to make progress in understanding this puzzle it is important to have as large as possible sample of @xmath10ii emitting galaxies to allow one to study the relationship between @xmath10ii emission and other physical properties . to this end we present here an analysis of emission line galaxies with strong @xmath0 emission in sdss data release 7 ( dr7 , * ? ? ? * ) . in section [ sec : data ] we discuss the sample selection and carefully account for agn emission . the physical properties of the @xmath10ii emitting galaxies are discussed in section [ sec : physical ] and the observed @xmath16 ratios are compared to model predictions in section [ sec : prediction ] . in section [ sec : origin ] we test these model predictions and investigate whether the presence of @xmath15 is associated with wr features . we find that low metallicity systems frequently do not show signs of wr stars . we discuss possible explanations for this finding in section [ sec : explanation ] and conclude in section [ sec : conclusion ] .

we present a sample of 2865 emission line galaxies with strong nebular emissions in sloan digital sky survey data release 7 and use this sample to investigate the origin of this line in star - forming galaxies . we also present an analysis of the physical properties of 189 star forming galaxies with strong emissions . we discuss possible reasons for this and possible mechanisms for the emission in these galaxies .

we present a sample of 2865 emission line galaxies with strong nebular emissions in sloan digital sky survey data release 7 and use this sample to investigate the origin of this line in star - forming galaxies . we show that star - forming galaxies and galaxies dominated by an active galactic nucleus form clearly separated branches in the versus\:\lambda6584}/{\ensuremath{\mathrm{h}\alpha}}$ ] diagnostic diagram and derive an empirical classification scheme which separates the two classes . we also present an analysis of the physical properties of 189 star forming galaxies with strong emissions . these star - forming galaxies provide constraints on the hard ionizing continuum of massive stars . to make a quantitative comparison with observation we use photoionization models and examine how different stellar population models affect the predicted emission . we confirm previous findings that the models can predict emission only for instantaneous bursts of 20% solar metallicity or higher , and only for ages of myr , the period when the extreme - ultraviolet continuum is dominated by emission from wolf - rayet stars . we find however that 83 of the star - forming galaxies ( 40% ) in our sample do not have wolf - rayet features in their spectra despite showing strong nebular emission . we discuss possible reasons for this and possible mechanisms for the emission in these galaxies . stars : wolf - rayet galaxies : evolution galaxies : stellar content galaxies : star formation

1111.4016

c

we have presented a simple physical picture of the qubit evolution due to its measurement in the circuit qed setup . the `` spooky '' back - action is universal , it is caused by gradual extraction of information about the qubit state . the `` realistic '' back - action is due to a specific mechanism : fluctuation of the photon number in the resonator . for a phase - sensitive amplifier the qubit evolution is described by eqs . ( [ ph - sens - diag ] ) and ( [ ph - sens - off-2 ] ) ; it is determined by the output signal @xmath5 , which corresponds to the amplified quadrature . for a phase - preserving amplifier the evolution is described by eqs.([ph - pres - diag ] ) and ( [ ph - pres - off-2 ] ) ; it is determined by two output signals : @xmath5 and @xmath6 , where @xmath5 now corresponds to the quadrature , which provides information about the qubit state ( @xmath89-quadrature in the resonator ) and @xmath6 corresponds to the orthogonal @xmath88-quadrature , which gives us a record of the photon number fluctuations in the resonator . while the cqed setup significantly differs from both the broadband quantum measurement setup @xcite and the standard optical setup @xcite , we see that the description of the qubit evolution is exactly the same as in both these cases if a phase - sensitive amplifier is used . the description is only slightly different when a phase - preserving amplifier is used : we should assign the `` spooky '' and `` realistic '' back - actions to the separate output signals @xmath5 and @xmath6 instead of only one signal . it is also useful to think about the phase - preserving case via the model in which we split the outgoing microwave ( the quantum signal ) into two equal parts and then use 90-degree - shifted phase - sensitive amplifiers for these two channels . we intentionally considered only the simplest case , because most of the further steps and generalizations are quite straightforward @xcite . in particular , it it very simple to include rabi oscillations and energy relaxation of the qubit state . for that we have to take time - derivative of the evolution equations and add the terms due to rabi oscillations and energy relaxation . if the stratonovich definition of the derivative is used , we get the equations of the bayesian formalism @xcite ; if the it derivative is used , we get the equations of the quantum trajectory formalism @xcite . generalization to measurement of several entangled qubits is also straightforward @xcite . we have considered only the resonant case , @xmath123 ; however , generalization to the case @xmath236 is quite simple ( see @xcite ) : we just need a different definition of the informational @xmath89-quadrature and photon - fluctuation @xmath88-quadrature . in our formalism we implicitly assumed sufficiently wide bandwidth of the amplifier ( much larger than the ensemble dephasing @xmath12 and rabi frequency @xmath128 ) . if this is not the case , the formalism should change significantly . however , we believe that in most of the practical cases we can take this effect into account by adding a classical narrowband filter to the classical signal at the amplifier output ; this will correspond to passing the signals @xmath5 and @xmath6 through the low - pass filters . a much more serious change of the theory is required when the resonator bandwidth @xmath115 is comparable to @xmath12 or @xmath128 ; this still has to be done . understanding the difference between the `` spooky '' and `` realistic '' back - actions is important for designing the quantum feedback control of the rabi oscillations @xcite . the simplest case is when a phase - sensitive amplifier amplifies the informational @xmath89-quadrature . then there is no `` realistic '' back - action , and the feedback loop should only modulate the amplitude of the rabi drive ( i.e. the rabi frequency @xmath128 ) ; this case was well studied for the broadband setup @xcite . the situation is different for a phase - preserving amplifier . then we need two feedback channels : the first ( usual ) channel should modulate the rabi frequency @xmath128 to compensate the `` spooky '' back - action , while the second channel should compensate the `` realistic '' back - action by modulating the qubit frequency @xmath237 or the the frequency of the rabi drive @xmath238 . the controller for the second feedback channel is quite simple : it should compensate the contribution @xmath239 to the qubit phase derivative @xmath240 due to the @xmath65-term in eq . ( [ ph - pres - off-2 ] ) . therefore the controller is ( _ qb-_r)= -k[q(t)-q ] , i.e. we should directly apply the signal @xmath6 to modulate @xmath237 or @xmath238 . the second feedback channel essentially eliminates the @xmath65-term in eq . ( [ ph - pres - off-2 ] ) and decreases the ensemble dephasing @xmath12 by @xmath241 . correspondingly , in the absence of the first ( main ) feedback channel the peak - to - pedestal ratio of the rabi peak increases from 2 to 4 in the quantum - limited case . the first feedback channel should be the same as for the broadband setup ; it depends on the signal @xmath5 and can be realized using various ideas for the controller ( `` direct '' , bayesian , `` simple '' , etc . @xcite ) . notice that _ without the second channel the feedback performance is determined by the quantum efficiency @xmath55 , while with the second channel it is determined by @xmath242 _ ( this is one more combination of the terms in eq . ( [ gamma ] ) , which can be used for the definition @xcite of quantum efficiency ) . the case of a phase - sensitive amplifier , which amplifies a non - optimal quadrature ( @xmath243 , @xmath244 ) is similar to the case of a phase - preserving amplifier , but both feedback channels should start with the same signal @xmath5 . _ in both the phase - sensitive and phase - preserving setups a perfect feedback control is possible in the quantum - limited case @xmath58 . _ discussion of the `` spooky '' and `` realistic '' back - actions in the cqed setup necessarily raises the question of causality . when the microwave leaves the resonator , it does not yet `` know '' in which way it will be measured ( phase - preserving or phase - sensitive , which angle @xmath13 , etc . ) . moreover , when a circulator is used for the outgoing microwave , the field in the resonator and the qubit can never `` know '' in a realistic way which method of measurement is used . nevertheless , the qubit evolution strongly depends on the measurement method . as we discussed , the `` spooky '' evolution moves the qubit state along the meridians of the bloch sphere , the `` realistic '' back - action moves the state along the parallels , and the measurement method determines whether the qubit experiences the `` spooky '' or `` realistic '' back - action ( or their combination ) . in this sense the `` realistic '' back - action is not fully realistic : it has the physical mechanism , but whether this mechanism works or not is determined in a spooky way . the causality requires that we can not pass a `` useful '' information to the qubit by choosing the measurement method . this means that _ the ensemble - averaged evolution of the qubit can not depend on the measurement method ( this is the general requirement of causality in quantum mechanics)_. it is surely satisfied in our cqed setup . the author thanks michel devoret , konstantin likharev , patrice bertet , and farid khalili for useful discussions . the work was supported by aro muri grant w911nf-11 - 1 - 0268 and by nsa / iarpa / aro grant w911nf-10 - 1 - 0334 . h. m. wiseman and g. j. milburn , phys . a * 47 * , 642 ( 1993 ) ; h. j. carmichael , _ an open system approach to quantum optics _ ( springer , berlin , 1993 ) ; h. m. wiseman and g. j. milburn , _ quantum measurement and control _ ( cambridge univ . press , 2009 ) .

we present a simple formalism describing evolution of a qubit in the process of its measurement in a circuit qed setup . when a phase - sensitive amplifier is used , the evolution depends on only one output quadrature , and the formalism is the same as for a broadband setup . when a phase - preserving amplifier is used , the qubit evolution depends on two output quadratures . in both cases a perfect monitoring of the qubit state and

we present a simple formalism describing evolution of a qubit in the process of its measurement in a circuit qed setup . when a phase - sensitive amplifier is used , the evolution depends on only one output quadrature , and the formalism is the same as for a broadband setup . when a phase - preserving amplifier is used , the qubit evolution depends on two output quadratures . in both cases a perfect monitoring of the qubit state and therefore a perfect quantum feedback is possible .

0911.4532

i

the number of discovered extrasolar planets has been increasing quickly since the first extrasolar planet , 51 pegasi b , was detected around a solar - type star @xcite . 51 pegasi b is the prototype of a class of exoplanets known as hot jupiters " because they are generally jupiter - mass planets located @xmath8 au from their parent stars and therefore their equilibrium temperatures are much higher than that of jupiter . the high temperature of the protoplanetary disk at the orbital radii where they are now provides an environment extremely different from where giant planets are expected to form via either the core - accretion model @xcite or the gravitational instability model @xcite . one of the most commonly adopted solutions is that hot jupiters have formed at larger orbital radii in the protoplanetary disk and then moved inward to their current locations via the disk - planet interactions ( e.g. * ? ? ? the magnetic fields of classical t tauri stars ( hereafter ctts ) are typically strong enough to truncate the inner regions of protoplanetary disks to the corotation radius , where the keplerian angular velocity of the disk is the same as the stellar - spin angular velocity , and create an inner magnetospheric cavity . besides , the migration due to the planet - disk interaction is expected to slow dramatically once a young hot jupiter passes the inner disk edge @xcite . the pile - up population of hot jupiters at @xmath9 au from their solar - type parent stars revealed from radial - velocity searches @xcite may be attributed to the existence of the cavity ( * ? ? ? * and references therein ) . on one hand , an attempt has been made by @xcite to search for a hot jupiter around a ctts , although @xcite substituted an explanation of a cool stellar spot for an orbiting hot jupiter . future observations will provide more evidence for planets of early ages . on the other hand , the simulated orbital evolution of giant planets as they migrate into the cavity was carried out by @xcite . their results suggest that high - mass hot jupiters would move closer to their central stars and even be destroyed because planet s entry into the magnetospheric cavity results in a growth in orbital eccentricity @xmath10 . although the eccentricity excitation is subject to the uncertain properties such as disk mass and viscosity , this model may provide a mechanism to pump up the eccentricity of a hot jupiter inside the cavity and in turn affect the orbital evolution of the planet via the tidal interactions between the star and planet . in addition , the magnetic interactions between the star and planet in the magnetospheric cavity would be important as well , which may be an upscale analogy to the magnetic interactions between jupiter and the galilean satellites ( * ? ? ? * and references therein ) . the coupled tidal evolution of the radius and orbit of hot jupiters in the absence of a disk has been investigated @xcite . to obtain noticeable influence on @xmath11 , the tidal heating is assumed to be deposited deep in the planet in these models @xcite . the purpose of @xcite and @xcite is to explain the large radii of some transiting hot jupiters using tidal heating . on the other hand , @xcite showed that for modest eccentricities , young hot jupiters of radius @xmath12 jupiter radii at @xmath13 au swell beyond two jupiter radii and their internal degeneracy is partially lifted on the timescale of @xmath14 gyrs . ] . thereafter , their thermal equilibria become unstable and they undergo runaway inflation until their radii exceed the roche radius . then roche lobe overflow ensues . under the assumption that the overflowing gas immediately loses its orbital angular momentum to the planet and plunges into the central star , these mass - losing planets migrate outwards , such that their semi - major axes and roche radii increase while their mass , eccentricity , and tidal dissipation rate decrease until the mass loss is quenched . of course , including a disk would change the orbital evolutions of roche - lobe - overflowing planets , as has been calculated by @xcite who do not consider the tidal expansion of @xmath11 and the magnetospheric cavity though . as more and more hot jupiters located @xmath15 au have been discovered by transit surveys for recent years , it is noteworthy that almost no giant planets of mass @xmath5 jupiter mass ( @xmath16 ) have been detected within @xmath17 au from their solar - type parent stars ( see figure [ correl ] ; also see * ? ? ? * and references therein ) . this puzzle may be attributed to the subsequent evolutions of hot jupiters after they enter the magnetospheric cavity of the protoplanetary disk . since thermal evaporation ( e.g. * ? ? ? * ) has not been undoubtedly identified to be the major cause ( * ? ? ? * and references therein ) , we shall discuss the potential implication of our model to explain the observation in the end of the paper . for the above reasons , in this work we concentrate on the orbital evolution of a young hot jupiter inside the magnetospheric cavity of a protoplanetary disk by taking into account the tidal and magnetic interactions between the star and planet . to restrict to the problem without significantly involving the planet - disk interaction for simplicity , we consider the evolution after the hot jupiter enters the 2:1 orbital resonance with the inner edge of a disk . the initial eccentricity , which is expected to be excited in the cavity before the planet migrates to the resonance location , is treated as one of the free parameters of the problem . the equations for the orbital and interior evolution of a hot jupiter inside a magnetospheric cavity are described in 2 . the results are presented in 3 , and are summarized and discussed in 4 .

the model takes into account the disk locking of stellar spin as well as the tidal and magnetic interactions between the star and the planet . the goal in this paper is to study how the orbital evolution inside the magnetospheric cavity depends on the cavity size , planet mass , and orbital eccentricity . in the present work ,

we present a simplified model to study the orbital evolution of a young hot jupiter inside the magnetospheric cavity of a proto - planetary disk . the model takes into account the disk locking of stellar spin as well as the tidal and magnetic interactions between the star and the planet . we focus on the orbital evolution starting from the orbit in the 2:1 resonance with the inner edge of the disk , followed by the inward and then outward orbital migration driven by the tidal and magnetic torques as well as the roche - lobe overflow of the tidally inflated planet . the goal in this paper is to study how the orbital evolution inside the magnetospheric cavity depends on the cavity size , planet mass , and orbital eccentricity . in the present work , we only target the mass range from 0.7 to 2 jupiter masses . in the case of the large cavity corresponding to the rotational period days , the planet of mass jupiter mass with moderate initial eccentricities ( ) can move to the region au from its central star in years , while the planet of mass jupiter mass can not . we estimate the critical eccentricity beyond which the planet of a given mass will overflow its roche radius and finally lose all of its gas onto the star due to runaway mass loss . in the case of the small cavity corresponding to the rotational period days , all of the simulated planets lose all of their gas even in circular orbits . our results for the orbital evolution of young hot jupiters may have the potential to explain the absence of low - mass giant planets inside au from their dwarf stars revealed by transit surveys .

0911.4532

i

we construct a simple model to study the orbital evolution of a young hot jupiter in an eccentric orbit inside a magnetospheric cavity of a proto - planetary disk around a ctts . for the sake of simplicity , we assume that the magnetospheric cavity of the protoplanetary disk is truncated by a stellar dipole field . through the magnetic linkage between the central star and the disk , the rotational period of the star is quickly locked by the inner edge of disk . we then introduce a young hot jupiter at @xmath20 and restrict ourselves to the orbital evolution of a hot jupiter inside the cavity . assuming that the planet behaves like a plasma , we apply the same formulism for the star - disk magnetic interaction to that for the star - planet interactions . we adopt the equilibrium - tide equations with @xmath179 and @xmath180 to model the star - planet tidal interactions . in so doing , our model focuses on the planet migration due to tidal and magnetic interactions between the planet and the star , and does not consider any interactions between the planet and the disk . however , as the size of the magnetospheric cavity evolves , the planet is artificially pushed to @xmath20 if it lies beyond @xmath20 . we vary three parameters @xmath32 ( @xmath181 and 1500 g ) , initial @xmath73 ( @xmath182 , 1 , 1.5 , 2 @xmath16 ) , and initial @xmath10 ( @xmath145 , @xmath183 , and @xmath148 ) in our simulations to investigate the fate of the planet migration under the influence of the cavity size , planet mass , and orbital eccentricity . two sizes of magnetospheric cavities are considered to approximately match the bimodal distribution of spin periods of young stars in the orion nebula cluster . the initial @xmath20 corresponding to the large ( small ) cavity opened up by the stronger ( weaker ) stellar fields is @xmath184 au ( @xmath185 au ) . in the case of the large cavity ( @xmath130 g ) , the planets require nonzero @xmath146 to enhance their tidal and magnetic interactions with their central stars and make significant inward migration . the migration rate increases with @xmath146 for a given planet mass . when @xmath146 is as large as the critical value @xmath148 , @xmath11 exceeds @xmath92 and the roche overflow occurs . for planets with different masses , massive planets ( @xmath186 ) have higher @xmath148 ( i.e. more intense tidal heating ) than less massive ones ( @xmath187 ) because massive planets are more difficult to thermally inflate due to their greater gravitational binding energies and cooling rates . as a result , stronger stellar tides raised by the planet with higher @xmath73 and @xmath146 allow for faster migration . overall , massive planets can therefore migrate further in than less massive ones , as shown in the simulations for @xmath150 . when @xmath149 , low - mass planets ( @xmath167 and 1 @xmath16 ) inflate by tidal heating faster than inward migration . hence they overflow their large roche lobes at large @xmath19 , resulting in the low density and therefore the runaway mass loss . on the other hand , the high - mass planets ( @xmath188 and 2 @xmath16 ) migrate inwards fast without significant tidal inflation . in contrast to the low - mass planets , once these planets fill their small roche lobe at small @xmath19 , their density is high enough that they can undergo stable l1 overflow . during this phase , tidal and magnetic interactions instead of tidal inflation drive them to lose mass , expand , and migrate outward . this stable mass - loss phase proceeds until these outward migrating planets are large enough to become unstable against mass loss . finally , they lose all gas to their central stars . in the case of the small cavity ( @xmath131 g ) , the simulated planets in circular orbits all quickly migrate in due to the fierce tidal and magnetic interactions until they stably overflow their roche radii . after that , they can move outwards due to the mass loss and move inwards again by the tidal and magnetic torques . as their mass goes down and their degeneracy is lifted , all of these planets are finally destroyed , suffering from the runaway mass loss as in the large - cavity case . to study the significance of the magnetic interactions between the star and the planet in our model , we also simulate the cases by shutting down the interaction ( i.e. @xmath170 ) . we found that the migration of less massive planets is more sensitive to the magnetic interaction , which is enhanced by their easily inflated radii . setting @xmath170 makes the migration rate of low - mass planets slower , as shown in the case for @xmath189 with @xmath190 in the large - cavity case . by contrast , the inward migration of massive planets is less sensitive to the magnetic interaction but more to the tidal interaction . as has been summarized in the preceding paragraph , all planets in the small cavity destruct under both the tidal and magnetic torques at such close - in initial positions from the stars even if @xmath145 . when @xmath170 , only the planet of @xmath137 can survive unless the low - mass planet starts with an eccentric orbit with @xmath178 . the model presented here for the orbital evolution of young hot jupiters is different from the works by @xcite and @xcite . in this work , we employ simple models including the star - planet interactions and disk locking , which are not considered by @xcite . furthermore , we take into account the planet expansion due to the adiabatic mass loss and model the mass loss rate using the approach in @xcite , whereas @xcite ignore the radius adjustment to the mass loss and use a free parameter to control the mass loss rate . ignoring the mass - radius relation during the roche - lobe overflow phase as done in @xcite , a roche - lobe filled giant planet with @xmath149 continuously loses its mass via tidal inflation and migrates outwards until the tidal heating rate is weaker than the cooling rate , leading to a survived planet of lower mass . on the other hand , @xcite consider young hot jupiters moving inwards via the type ii migration without a magnetospheric cavity and tidal inflation . in their work including the mass - radius relation , once the planets of mass @xmath191 get close enough to their central stars and therefore overflow their roche lobes , they migrate outwards and finally lose all their mass onto the star . in this regard , our results are compatible with theirs . one of the major differences is that the mass loss is driven by the type ii migration in the model by @xcite , while in our work the mass loss is driven by the loss of orbital angular momentum via the tidal and magnetic interactions with the parent star whose spin is almost locked by the disk . moreover , the planets of mass @xmath192 with @xmath193 survive in the cavity during the ctts phase in our model . for the last few years , transit surveys have revealed the peculiar @xmath194 correlation for hot jupiters : less massive hot jupiters ( @xmath195 jupiter mass ) are almost absent within @xmath196 au from their parent dwarf stars of the ages @xmath14 gyrs . our results show that during the ctts phase , planets of @xmath197 with modest initial eccentricities ( @xmath198 ) and sufficient magnetic interactions in a large cavity can migrate to @xmath199 au , while planets of @xmath200 can not . more specifically , given @xmath193 , the planet of @xmath134 can safely arrive at @xmath201 au and the planet of @xmath135 can get to @xmath202 au in the end of our simulations . whether or not these planets can further migrate toward their spun - down parent stars during the main - sequence phase depends on @xmath68 , which is not yet well understood . @xcite suggested that @xmath68 induced by hot jupiters may become large ( i.e. @xmath203 ) as cttss evolve to main - sequence stars based on their dynamical - tide model . as they and others @xcite pointed out , we would be extremely fortunate to observe these very close - in hot jupiters if the current @xmath204 , implying that @xmath68 of the solar - type main - sequence host stars may be quite large . however , it should be noted that these very close - in planets were all discovered by transit surveys ( see figure [ correl ] ) . although transit surveys overall prefer to detect close - in planets @xcite , the detectability of a hot jupiter as a function of the semi - major axis of interest here ( i.e. @xmath205 au ) is extremely ill - defined as the various transit surveys are subject to different observational limitations such as the transit depth , sampling rate , red noise , and detection threshold @xcite . if @xmath68 indeed gradually becomes @xmath203 as cttss evolve to main - sequence stars , therefore allowing the planets to move a little bit inward during the short transition after @xmath152 years while halting the further planet migration for most of the main - sequence phase , our model may have the potential to explain the absence of low - mass hot jupiters within @xmath206 au . on the other hand , a large body of studies have suggested that @xmath207 associated with the tidal dissipation induced by the hot jupiters in main - sequence dwarfs could be as small as @xmath129 . as a result of the efficient tidal dissipation , the orbits of the hot jupiters can decay so significantly that the planets may plunge into their host stars during the main - sequence phase @xcite . this accretion " model may account for the paucity of the extremely close - in hot jupiters concluded from radial - velocity surveys ( * ? ? ? * also see figure [ correl ] ) . in addition , the relatively young ages of the extremely close - in hot jupiters revealed by transit surveys may also lend support to the model @xcite . although the planet - metallicity correlation independent of the spectral type does not seem to favor the accretion model @xcite , excessive heavy elements in the shallow convection zone of high - mass dwarfs may be able to sink down to the radiative zone via the double diffusive effect , thereby eliminating the metallicity enhancement and resolving the problem for the model @xcite . furthermore , @xcite found an excess spin of the host stars of hot jupiters , which may arise from tidal spin - up , although the uncertainty of the stellar ages and the limitation of a small number of samples demand more detections in the future to confirm the conclusion . the study by @xcite for the accretion model is carried out based only on one - mass case ( i.e. @xmath136 ) . if the accretion model is the main cause responsible for the observed @xmath194 relation , it would be expected that the extremely close - in giant planets of mass @xmath208 of younger ages should also be detected by transit surveys . the orbital decay timescale during the main - sequence phase due only to the tidal dissipation is given by @xmath209 ( see equation([eq : j*dot ] ) ) . in the case of a planet of 0.7@xmath210 , the planet can survive in @xmath211 yrs from the distance of @xmath196au at @xmath212 myrs . in contrast , the orbit of a planet of @xmath213 will decay on the timescale of @xmath214 yrs from a distance of @xmath215au at @xmath212 myrs . in other words , during the main - sequence phase , less massive planets excite weaker tides on their parent stars and therefore still stay outside @xmath216 au , while the massive planets keep falling into the stars in the way as interpreted by @xcite and @xcite . the recently discovered hot jupiter wasp-18b with an orbital period of 0.94 days and a mass of @xmath217 may provide a contraint on @xmath218 of a main - sequence star in the next few years @xcite . in this paper , we have attempted to bring several physical components to the context of the evolution of young hot jupiters . nonetheless , a large number of assumptions have been made to simplify the physical processes included in our model . the structure of the truncated disk is not modelled . how a planet migrates to @xmath20 and how the eccentricity evolves during its entry to the cavity ( e.g. * ? ? ? * ) are not addressed . the disk accretion rate is assumed to be quasi - steady to determine the cavity sizes , while observations show otherwise ( e.g. * ? ? ? the dipole configuration of the stellar fields connecting to the disk ignores any types of winds even though the effect of disk locking is introduced in a simplified manner to imitate the sink of the total angular momentum in our model . the star - planet magnetic interactions are parameterized to scale with the poynting flux at the magnetopause of the planet rather than appealing to any specific models , such as the dissipation due to the alfvn waves and unipolar inductor ( e.g. * ? ? ? * ) or induced by tilted stellar dipole fields ( e.g. laine et al . 2008 ; cf . papaloizou 2007 ) . the values of @xmath68 and @xmath69 chosen for the calculations are quite arbitrary ; we have not explored a wide range of the values . the interior structure of an inflated planet and the mass - radius relation of a hot jupiter are inferred from the 1-d numerical simulation @xcite even for a roche - lobe filled planet . also , the code ignores thermal properties of the solid core of a giant planet , leaving a question as to what would happen to the core under the intense tidal heating . in a hot jupiter - star system , the mass loss may occur via the lagrangian 2 point as well @xcite , which is not considered in the present work . besides , the mass loss from a planet in an eccentric orbit may be intermittent and nonconservative , while the mass loss rate in our calculation is simply estimated from the l1 overflow at @xmath219 . to use a more appropriate expression for the roche radius and to consider the more realistic mass loss in asynchronous eccentric planetary systems , a more careful treatment ( e.g. * ? ? ? * ) is desired to refine the results . in light of these limitations and possible uncertainties , the simulations covering a wide range of the parameter space along with more realistic modelling on individual issues will be explored in a future work . we are grateful to g. i. ogilvie , f. pont , and r. e. taam for useful discussions . this work has been supported by the nsc grant in taiwan through nsc 98 - 2112-m-001 - 011-my2 .

we present a simplified model to study the orbital evolution of a young hot jupiter inside the magnetospheric cavity of a proto - planetary disk . we only target the mass range from 0.7 to 2 jupiter masses . in the case of the large cavity corresponding to the rotational period days , the planet of mass jupiter mass with moderate initial eccentricities ( ) can move to the region au from its central star in years , while the planet of mass jupiter mass can not . our results for the orbital evolution of young hot jupiters may have the potential to explain the absence of low - mass giant planets inside au from their dwarf stars revealed by transit surveys .

we present a simplified model to study the orbital evolution of a young hot jupiter inside the magnetospheric cavity of a proto - planetary disk . the model takes into account the disk locking of stellar spin as well as the tidal and magnetic interactions between the star and the planet . we focus on the orbital evolution starting from the orbit in the 2:1 resonance with the inner edge of the disk , followed by the inward and then outward orbital migration driven by the tidal and magnetic torques as well as the roche - lobe overflow of the tidally inflated planet . the goal in this paper is to study how the orbital evolution inside the magnetospheric cavity depends on the cavity size , planet mass , and orbital eccentricity . in the present work , we only target the mass range from 0.7 to 2 jupiter masses . in the case of the large cavity corresponding to the rotational period days , the planet of mass jupiter mass with moderate initial eccentricities ( ) can move to the region au from its central star in years , while the planet of mass jupiter mass can not . we estimate the critical eccentricity beyond which the planet of a given mass will overflow its roche radius and finally lose all of its gas onto the star due to runaway mass loss . in the case of the small cavity corresponding to the rotational period days , all of the simulated planets lose all of their gas even in circular orbits . our results for the orbital evolution of young hot jupiters may have the potential to explain the absence of low - mass giant planets inside au from their dwarf stars revealed by transit surveys .

1203.1048

i

symmetry breaking is a crucial aspect of modern particle physics . in particular the symmetry breaking sectors of theories extending the standard model are studied intensively . many of the most puzzling problems in generic standard model extensions , such as the gauge hierarchy and parameter proliferation problems , arise because of the use of elementary scalar fields to spontaneously break symmetries . deeper insights into both the physics and mathematics of symmetry breaking are thus worth having . the majority of model building scenarios consider a gauge symmetry @xmath0 which is spontaneously broken to a subgroup @xmath5 . of special interest here are models where @xmath0 is broken simultaneously to several isomorphic but differently embedded subgroups @xmath5 . below we enumerate several general classes of models where this mechanism is apparent . in such models , each isomorphically embedded subgroup is given by @xmath6 for some @xmath7 , and is identified with a point in the vacuum manifold @xmath3 . for a higgs field in a @xmath0 representation and an associated basis of weights for this representation , we develop explicit mathematical formulas for writing each state in the vacuum manifold as a linear combination of the weights . to make our result accessible to the model - building audience at large , we provide a careful review of the necessary mathematical tools which belong to the discipline of representation theory . we shall also explain all our mathematical results in the physical context of spontaneous symmetry breaking . in the adjoint representation the weights are the roots , and there exists a basis of weights for this adjoint representation which are known as the simple roots . these can be pulled back to define a cartan subalgebra @xmath8 , consisting of adjoint higgs vacuum expectation values ( vevs ) which cause the symmetry to break along @xmath9 . our formalism identifies the vacuum manifold @xmath3 which belong to the vector space spanned by the cartan subalgebra . the elements of the vacuum manifold are related by a weyl group symmetry . given an adjoint higgs vacuum expectation value , @xmath10 , breaking @xmath11 , a full complement of vevs breaking @xmath0 to different cartan preserving embeddings of the subgroup @xmath5 can be obtained through this method . we give an explicit formula for recovering each vev . in our treatment , we shall concentrate on a specific and relevant case for high - energy physics model building scenarios , where @xmath5 stabilizes the highest weight of the lowest dimensional fundamental representation . this case in fact admits the simplest formula for recovering all vevs breaking @xmath11 , when the cartan subalgebra for @xmath5 is a subset of the cartan subalgebra for @xmath0 . the results presented here may provide direct solutions to problems in high - energy physics research . this includes problems arising in : * grand unified theories ( guts ) , where so - called `` flipped '' models arise whenever there are alternative embeddings of a given gut inside a larger gut @xcite . * domain - wall brane scenarios which use the `` clash of symmetries '' mechanism @xcite this idea was the main motivation for us to pursue the present study.[item : domain - wallbranes ] * the low - energy limit of yang - mills theory @xcite.[item : yang - mills ] * whenever there are multiple copies @xmath12 of a given representation of higgs fields , with vevs @xmath13 breaking the gauge group to isomorphic but differently embedded subgroups . this is a special case of what is generally termed `` vacuum alignment '' . each of these physical contexts is reviewed in more detail in the next section . to show explicitly how our results can be utilized we apply them to two model building examples from the literature , ref . @xcite and ref . @xcite , corresponding to contexts ( ii ) and ( iii ) listed above . it would also be possible to apply these techniques to help identify standard model particles embedded in representations of a grand - unified gauge group @xcite , and to help classify and construct different chains of embeddings in the context of grand unification @xcite . we have kept our analysis general and there may well be other applications for different embeddings of isomorphic subgroups . we focus on presenting our results in a self contained and accessible manner . we include examples of how our results relate to problems in the high - energy physics literature and explicitly apply the techniques developed here to the field . we are keen to ensure the dialogue is bicultural and accessible to mathematicians as well as physicists . follow the introduction , we begin in sec . [ sec : motivation ] by providing a thorough physical motivation by discussing four model building scenarios . [ sec : notation ] gives the necessary notation , and in secs . [ sec : weylgroups]-[sec : embeddings ] we motivate and explain the representation theory needed to understand the proof of the main result . the proof itself appears in sec . [ sec : proof ] , where we clearly state the formula for recovering the adjoint higgs vevs which break @xmath0 to different embeddings of a subgroup @xmath5 as linear combinations of vevs breaking @xmath0 along the chain @xmath14 . we also treat the relation between the weights of vevs causing @xmath0 to break to different embeddings of a subgroup @xmath5 , for a non - adjoint higgs field . in sec . [ sec : applyresults ] we explicitly apply the main result to two concrete examples from the contemporary physics literature , thus placing our results in the context of model building scenarios . we conclude in sec . [ sec : conclusion ] .

we present a systematic approach to finding higgs vacuum expectation values , which break a symmetry to differently embedded isomorphic copies of a subgroup . we give an explicit formula for recovering each point in the vacuum manifold of a higgs field which breaks . these results are illustrated explicitly for adjoint higgs fields and clearly linked to the mathematical formalism of weyl groups . we use the final section to explicitly demonstrate how our work contributes to two contemporary high - energy physics research areas .

we present a systematic approach to finding higgs vacuum expectation values , which break a symmetry to differently embedded isomorphic copies of a subgroup . we give an explicit formula for recovering each point in the vacuum manifold of a higgs field which breaks . in particular we systematically identify the vacuum manifold with linear combinations of the vacuum expectation values breaking . we focus on the most applicable case for current work on grand unified theories in extra dimensional models and low - energy effective theories for quantum chromodynamics . here the subgroup , , stabilizes the highest weight of the fundamental representation leading to a simple expression for each element of the vacuum manifold ; especially for an adjoint higgs field . these results are illustrated explicitly for adjoint higgs fields and clearly linked to the mathematical formalism of weyl groups . we use the final section to explicitly demonstrate how our work contributes to two contemporary high - energy physics research areas .

0807.2645

c

we have applied an existing monte - carlo ly@xmath0 radiative transfer code ( described and tested extensively in * ? ? ? * ) to the calculation of the pressure that is exerted by ly@xmath0 photons on an optically thick medium . this code enabled us to perform ( the first ) direct , accurate calculations of ly@xmath0 radiation pressure , which distinguishes this work from previous discussions on the importance of ly@xmath0 radiation pressure in various astrophysical environments . we have focused on a range of models which represent galaxies at different cosmological epochs . in [ sec : firststar ] we have shown that the ly@xmath0 radiation pressure exerted on the neutral intergalactic medium ( igm ) surrounding minihalos ( @xmath231 ) in which the first stars form , can exceed gravity by 23 orders of magnitude ( fig [ fig : casei ] ) , and in principle accelerate the gas in the igm to tens of km s@xmath1 . thus , ly@xmath0 radiation pressure can launch supersonic winds in the igm surrounding the first stars . our analysis did not allow a detailed study of the consequences of these winds . a comprehensive study would require numerical simulations that capture the full igm density field around minihalos in 3d and track the evolution of the shocks that may form in the igm together with the ly@xmath0 radiative transfer . in this paper , we have also shown that ly@xmath0 radiation pressure is important in the neutral igm that surrounds the hii regions produced by galaxies with a total halo mass of @xmath190 ( fig [ fig : caseii ] . these are the lowest mass , and hence the most abundant , halos in which gas can cool via atomic line excitation . here , however , the absolute magnitude of the radiation force is too weak to drive the gas to supersonic velocities . finally , we have shown in [ sec : wind ] that the ly@xmath0 radiation pressure exerted on neutral gas in the interstellar medium ( ism ) of a galaxy can also have strong dynamical consequences . in particular , we have found that the ly@xmath0 radiation force exerted on an expanding hi supershell can exceed gravity by orders of magnitude ( fig [ fig : caseiii ] ) , for reasonable assumptions about the gravitational force . it is therefore possible that ly@xmath0 radiation pressure plays an important role in determining the kinematics of hi supershells around starburst galaxies . we have demonstrated that the total ly@xmath0 radiation force on a spherical hi supershell can be written as @xmath232 , where the force - multiplication factor @xmath214 relates to the average trapping time of ly@xmath0 photons in the neutral medium . the factor @xmath214 can greatly exceed unity , as illustrated by fig [ fig : fscat ] . for comparison , the maximum possible radiation force due to continuum radiation ) around late - type stars that may significantly exceed @xmath233 @xcite . this is not because of trapping of continuum photons , but related to the propagation speed of the photons and the wind . we similarly expect the radiative force of trapped ly@xmath0 photons in steady - state outflows to potentially exceed @xmath234 ( and as argued in this paper , it is possible that @xmath235 ) . note though that these steady - state outflows are clearly different from those discussed in [ sec : wind ] , in which a well defined thin shell hi gas is physically separated from the central ly@xmath0 source . ] is @xmath236 , in which @xmath237 is the bolometric luminosity of the central galaxy . for a typical star forming galaxy , @xmath238 ( e.g. * ? ? ? * ) , whereas for a galaxy that contains population iii stars , @xmath239 @xcite . hence , the ly@xmath0 radiation pressure can dominate the maximum possible continuum radiation pressure if @xmath240 ( for a normal stellar population ) , a threshold which is easily exceeded at large column densities of relatively slow - moving hi shells ( see fig [ fig : fscat ] ) . the possibility that ly@xmath0 radiation alone can result in a radiation force that exceeds @xmath236 is important . @xcite have shown that the total momentum carried by radiation from a star - forming region can exceed the total momentum deposited by supernova explosions in it , and so galactic outflows may be driven predominantly by continuum radiation pressure . we have argued that ly@xmath0 radiation pressure may in some cases be even more important than continuum radiation pressure , and thus provide the dominant source of pressure on neutral hydrogen in the ism . the important implication of our last result is that ly@xmath0 radiation pressure may drive outflows of hi gas in the ism . observations of local starburst galaxies have shown that the presence of outflowing hi gas may be required to avoid complete destruction of the ly@xmath0 radiation by dust and to allow its escape from the host galaxies @xcite . at high redshifts , the ly@xmath0 emission line of galaxies is often redshifted relative to other nebular recombination lines ( such as h@xmath0 ) and metal absorption lines ( e.g. * ? ? ? * ; * ? ? ? furthermore , the spectral shape of the ly@xmath0 emission line is typically asymmetric , with emission extending well into the red wing of the line ( e.g. * ? ? ? * ) . both of these observations can be explained simultaneously if the observed ly@xmath0 photons scatter off neutral hydrogen atoms in an outflowing supershell of hi gas that surrounds the star forming regions @xcite . the possibility that ly@xmath0 radiation pressure may be important in determining the properties of expanding supershells is exciting , and is discussed in more detail in a companion paper ( dijkstra & loeb 2008 ) . * acknowledgments * this work is supported by in part by nasa grant nnx08al43 g , by fqxi , and by harvard university funds . we thank christian tapken and an anonymous referee for helpful constructive comments . xx natexlab#1#1 abel , t. , norman , m. l. , & madau , p. 1999 , apj , 523 , 66 abel , t. , bryan , g. l. , & norman , m. l. 2002 , science , 295 , 93 abel , t. , wise , j. h. , & bryan , g. l. 2007 , apjl , 659 , l87 adams , t. f. 1975 , apj , 201 , 350 ahn , s .- h . , & lee , h .- w . 2002 , journal of korean astronomical ahn , s .- h . , lee , h .- w . , & lee , h. m. 2003 , mnras , 340 , 863 ahn , s .- h . 2004 , apjl , 601 , l25 atek , h. , kunth , d. , hayes , m. , ostlin , g. , mas - 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we show that the radiation force that ly photons exert on hydrogen gas in the neutral intergalactic medium ( igm ) , that surrounds minihalos that host the first stars , may exceed gravity by orders of magnitude and drive supersonic winds . ly radiation pressure may also dominate over gravity in the neutral igm that surrounds the hii regions produced by the first galaxies . furthermore , we show that ly radiation pressure may drive outflows in the interstellar medium of star forming galaxies that reach hundreds of km s .

we present accurate monte - carlo calculations of ly radiation pressure in a range of models which represent galaxies during various epochs of our universe . we show that the radiation force that ly photons exert on hydrogen gas in the neutral intergalactic medium ( igm ) , that surrounds minihalos that host the first stars , may exceed gravity by orders of magnitude and drive supersonic winds . ly radiation pressure may also dominate over gravity in the neutral igm that surrounds the hii regions produced by the first galaxies . however , the radiation force is likely too weak to result in supersonic outflows in this case . furthermore , we show that ly radiation pressure may drive outflows in the interstellar medium of star forming galaxies that reach hundreds of km s . this mechanism could also operate at lower redshifts , and may have already been indirectly detected in the spectral line shape of observed ly emission lines . [ firstpage ] cosmology : theory galaxies : high redshift radiation mechanisms : general radiative transfer ism : bubbles

1703.08969

i

atomic clocks based on optical lattices are capable of proffering outstanding stable and accurate time keeping devices . a fundamental feature of an optical lattice clock is that it interrogates an optical transition with the controlled atomic motion @xcite . at present , the most stable clock is based on the optical lattices of @xmath2sr atoms with accuracy below @xmath3 @xcite . the unique feature of this clock is that the atoms are trapped at the wavelengths of an external electric field at which the differential light shift of an atomic transition nullifies . these wavelengths are commonly known as the magic wavelengths ( @xmath0 ) @xcite . however , ions provide more accurate atomic clocks since various systematics in the ions can be controlled better @xcite . as a result a number of ions , such as , @xmath4al@xmath5 @xmath6hg@xmath5 , @xmath7yb@xmath5 , @xmath8in@xmath5 , @xmath9sr@xmath5 , @xmath10ca@xmath5 , @xmath11cd@xmath5 etc . are under consideration for building accurate clocks . among the various ions proposed for frequency standards @xcite , the alkaline earth metal ions possess an advantage that transitions required for cooling and re - pumping of ions and clock frequency measurement can be easily accessed using non - bulky solid state or diode lasers @xcite . moreover presence of metastable @xmath12 states in these ions , whose lifetimes range from milliseconds to several seconds , assist in carrying out measurements meticulously . the recent development on measurement of @xmath0 in a singly charged @xmath10ca@xmath5 ion has now open - up a platform for the possibility of building up pure optical trapped ion clocks @xcite . optical lattices blended with unique features of optical transitions in an ionic system can revolutionize the secondary as well as primary frequency standards . however , the potential of the optical dipole trap perturb the energy levels of the ion unevenly and the consistency of an ion optical clock depreciates . therefore , knowledge of @xmath0 values in these ions would be instrumental for constructing all - optical trapped ion clocks . these wavelengths can be found out using accurate values of the dynamic dipole polarizabilities @xmath1 of the states associated with the clock transitions . also , information on the dynamic ( @xmath1 ) values , especially at which the ions are being trapped will be of great significance . improved atomic clocks will obviously ease the widely used technologies including precise determination of fundamental constants @xcite , accurate control of quantum states @xcite and advancement in communication , global positioning system @xcite etc . following the measurement of @xmath0 in the @xmath13 transition of @xmath14ca@xmath5 , we had investigated these values in the @xmath15 and @xmath16 transitions of the alkaline - earth ions @xcite for the ground state principal quantum number @xmath17 . however , those studies were focused mainly on the linearly polarized light limiting the choice for experimental measurements . application of circular polarized light to atomic systems introduce contributions from the vector polarizabilities in the stark shifts of the energy levels , which is linearly proportional to the angular frequency of the applied field . this can help in manipulating the stark shifts in the energy levels and can lend to more degrees of freedom to attain further @xmath0 values as per the experimental stipulation . moreover , it is advantageous to consider hyperfine transitions in certain isotopes of the singly charged alkaline - earth ions , giving rise to zero hyperfine angular momentum , to get - rid off the systematics due to electric quadrupole shifts @xcite . since @xmath18 values of atomic and hyperfine states in an atomic system are different when vector and tensor components of @xmath18 contribute , the @xmath0 values also differ between the atomic and hyperfine transitions . thus , it would be pertinent to investigate @xmath0 both in the atomic and hyperfine transitions before the experimental consideration of the proposed ions . in fact , it could be more convenient to have @xmath0 that are independent of choice of both magnetic and hyperfine sub - levels in a given clock transition . in fact , the nd : yag lasers at 1064 nm is often used for trapping atoms and ions because of their relatively high power and low intensity noise @xcite . traps built with long wavelength lasers are generally `` high - field - seeking '' where the atoms are attracted to the intensity maxima . dynamic polarizabilities for the considered ions at 1064 nm will be of immense interest to the experimentalists since these polarizabilities will be immediately useful for operating optical traps at 1064 nm light fields . lccccccc + & & + & @xmath19 & & @xmath19 & @xmath20 & & @xmath19 & @xmath20 + + @xmath21 & 24.38(6 ) & @xmath21 & 19.24(5 ) & @xmath2219.24(5 ) & @xmath23 & 22.77(8 ) & @xmath2222.77(8 ) + @xmath24 & 0.07 & @xmath25 & 0.011 & @xmath220.011 & @xmath26 & 0.016 & @xmath220.016 + @xmath27 & 0.01 & @xmath28 & 3.76 & 3.009 & @xmath29 & 0.12 & 0.14 + @xmath23 & 48.4(17 ) & @xmath26 & 0.0027 & 0.002 & @xmath30 & 0.056 & 0.06 + @xmath31 & 0.01 & @xmath32 & 2.49(1 ) & @xmath220.49 & @xmath29 & 2.39(14 ) & @xmath220.85 + @xmath33 & 0.019 & @xmath34 & 0.81 & @xmath220.16 & @xmath35 & 0.76 & @xmath220.27 + & & @xmath30 & 0.36 & @xmath220.07 & @xmath36 & 0.001 & @xmath220.0005 + main"@xmath37 & 72.88 & & 26.67 & @xmath2216.96 & & 26.12 & @xmath2223.71 + @xmath38 & 3.25 & & 3.25 & & & 3.25 & + tail " @xmath37 & 5.86@xmath39 & & 3.75 & @xmath220.75 & & 3.75 & @xmath221.08 + @xmath40 & @xmath228.85@xmath39 & & @xmath227.94@xmath41 & & & @xmath221.02@xmath39 & + @xmath42(present ) & 76.1(2 ) & & 33.67(1.8 ) & @xmath2217.71 & & 33.11(1.8 ) & @xmath2224.78(4 ) + @xmath42(other ) @xcite & 75.28 & & 32.99 & @xmath2217.88 & & 32.81 & @xmath2225.16 + @xmath42(other ) @xcite & 73.0(1.5 ) & & 28.5(1.0 ) & @xmath2215.8(7 ) & & 29.5(1.0 ) & @xmath2222.45(5 ) + @xmath42(other ) @xcite&75.49 & & 32.73 & @xmath2217.64 & & 32.73 & @xmath2225.20 + @xmath42(expt . ) @xcite & 75.3(4 ) & & & & + + & & + & @xmath19 & & @xmath19 & @xmath20 & & @xmath19 & @xmath20 + + @xmath24 & 29.47(10 ) & @xmath24 & 38.67(2 ) & @xmath2238.67(2 ) & @xmath31 & 44.16(3 ) & @xmath2244.16(3 ) + @xmath43 & 0.0008 & @xmath44 & 0.0063 & @xmath220.0063 & @xmath45 & 0.015 & @xmath220.015 + @xmath46 & 0.071 & @xmath31 & 7.024(2 ) & 5.62(2 ) & @xmath29 & 0.33 & 0.37 + @xmath31 & 56.93(27 ) & @xmath45 & 0.003 & 0.002 & @xmath30 & 0.12 & 0.13 + @xmath47 & 0.0015 & @xmath29 & 6.63(7 ) & @xmath221.33 & @xmath29 & 6.51(5 ) & @xmath222.32(2 ) + @xmath48 & 0.0058 & @xmath34 & 1.76 & @xmath220.35 & @xmath35 & 1.72 & @xmath220.61 + & & @xmath30 & 0.72 & @xmath220.14 & @xmath36 & 0.69 & @xmath220.25 + main"@xmath37 & 86.47 & & 54.81 & @xmath2234.88 & & 53.55 & @xmath2246.85 + @xmath38 & 4.98 & & 4.98 & & & 4.98 & + tail"@xmath37 & 1.96@xmath39 & & 4.94 & @xmath221.0 & & 4.96 & @xmath221.44 + @xmath40 & @xmath220.19 & & @xmath221.77@xmath41 & & & @xmath222.78@xmath39 & + @xmath42(present ) & 91.23(0.3 ) & & 64.7(2.5 ) & @xmath2235.88(5 ) & & 63.5(2.5 ) & @xmath2248.29(7 ) + @xmath42(other ) @xcite & 89.99 & & 61.77 & - & & 61.77 & - + @xmath42(other ) @xcite&88.29(1.0 ) & & 61.43(52 ) & 35.42 & & 62.87(75 ) & @xmath2248.83(30 ) + @xmath42(expt . ) @xcite & 93.3(9 ) & & 57.0 & - & & 57.0 & - + + & & + & @xmath19 & & @xmath19 & @xmath20 & & @xmath19 & @xmath20 + + @xmath43 & 40.23(14 ) & @xmath43 & 22.51(13 ) & @xmath2222.51(13 ) & @xmath47 & 25.66(1 ) & @xmath2225.66(1 ) + @xmath49 & 0.005 & @xmath46 & 0.075 & @xmath220.074 & @xmath48 & 0.13 & @xmath220.13 + @xmath50 & 0.009 & @xmath47 & 3.86 & 3.095 & @xmath29 & 0.668(5 ) & 0.763(2 ) + @xmath47 & 73.93(4 ) & @xmath48 & 0.023 & 0.018 & @xmath51 & 0.0955(1 ) & 0.109(2 ) + @xmath52 & 0.011 & @xmath29 & 11.85(3 ) & @xmath222.37 & @xmath53 & 13.34(13 ) & @xmath224.76(5 ) + @xmath54 & 0.013 & @xmath51 & 1.76 & @xmath220.35 & @xmath35 & 2.863(34 ) & @xmath221.022(17 ) + main"@xmath37 & 114.19 & & 40.07 & @xmath2222.19 & & 42.76 & @xmath2230.71 + @xmath38 & 9.35 & & 9.35 & & & 9.35 & + tail"@xmath37 & 1.66@xmath39 & & 4.75 & @xmath221.0 & & 4.79 & @xmath221.46 + @xmath40 & @xmath220.37 & & @xmath222.34@xmath39 & & & @xmath223.87@xmath39 & + @xmath42(present ) & 123.7(5 ) & & 54.17(2.5 ) & @xmath2222.19(4 ) & & 56.87(2.4 ) & @xmath2232.17(3 ) + @xmath42(other ) @xcite & 124.26(1.0 ) & & 48.81(46 ) & @xmath2224.62(28 ) & & 50.67(58 ) & @xmath2230.85(31 ) + @xmath42(other ) @xcite & 123.88(5 ) + in the present work , we aim to search for the @xmath0 for the @xmath55 optical clock transitions , both in the atomic and hyperfine levels , in @xmath14ca@xmath5 ( with nuclear spin @xmath56=7/2 ) , @xmath2sr@xmath5 ( @xmath56=9/2 ) and @xmath57ba@xmath5 ( @xmath56=3/2 ) ions using circularly polarized light . these values can be compared with the values for the linearly polarized light reported in ref . @xcite for the experimental consideration to trap the above ions . also , we had demonstrated in a recent work how a trap geometry can be chosen in such a way that stark shifts observed by the energy levels can be free from the contributions from the vector and tensor components of the @xmath18 of the atomic states @xcite . assuming such trapping geometries for the considered alkaline - earth ions , we also give @xmath0 values using only the scalar polarizability contributions . moreover , we identify the tune - out wavelengths ( @xmath58 ) of the respective states for which the dynamic dipole polarizability of these ions vanishes . comprehension of these @xmath58 values are needed for the sympathetic cooling of other possible singly and multiply charged ions in two - species mixtures with the considered alkaline earth ions @xcite . we also present dynamic polarizability of these states at the 1064 nm wavelength of the applied external electric field . contributions from various electric dipole ( e1 ) matrix elements in determining the @xmath18 values and the role of the electron correlation effects for the evaluation of accurate values of the e1 matrix elements are also discussed . unless stated otherwise , all the results are given in atomic unit ( a.u . ) throughout this paper .

rev . a * 92 * , 031402(r ) ( 2015 ) ] for the linearly polarized light . moreover , the actual clock transitions in these ions are carried out among the hyperfine levels . the values in these hyperfine transitions are estimated and found to be different from for the atomic transitions due to different contributions coming from the vector and tensor part of . importantly , we also present values that depend only on the scalar component of for their uses in a specially designed trap geometry for these ions so that they can be used unambiguously among any hyperfine levels of the atomic states of the clock transitions . accurate values of the electric dipole matrix elements required for these studies are given and trends of electron correlation effects in determining them are also highlighted .

we present additional magic wavelengths ( ) for the clock transitions in the alkaline - earth metal ions considering circular polarized light aside from our previously reported values in [ j. kaur et al . , phys . rev . a * 92 * , 031402(r ) ( 2015 ) ] for the linearly polarized light . contributions from the vector component to the dynamic dipole polarizabilities ( ) of the atomic states associated with the clock transitions play major roles in the evaluation of these , hence facilitating in choosing circular polarization of lasers in the experiments . moreover , the actual clock transitions in these ions are carried out among the hyperfine levels . the values in these hyperfine transitions are estimated and found to be different from for the atomic transitions due to different contributions coming from the vector and tensor part of . importantly , we also present values that depend only on the scalar component of for their uses in a specially designed trap geometry for these ions so that they can be used unambiguously among any hyperfine levels of the atomic states of the clock transitions . we also present values explicitly at the 1064 nm for the atomic states associated with the clock transitions which may be useful for creating `` high - field seeking '' traps for the above ions using the nd : yag laser . the tune out wavelengths at which the states would be free from the stark shifts are also presented . accurate values of the electric dipole matrix elements required for these studies are given and trends of electron correlation effects in determining them are also highlighted .

1703.08969

m

as discussed in our earlier works @xcite , each component of @xmath134 can be conveniently evaluated in the considered alkaline earth ions , in which many of the low - lying states have electronic configurations as a common closed core of inert gas atoms and a well defined valence orbital , by classifying into three different contributions such as @xmath135 where @xmath38 , @xmath40 and @xmath37 are referred to as the core , core - valence and valence electron correlation contributions , respectively . since the valence electron correlation effects are mainly estimated by @xmath37 , this gives majority contribution followed by @xmath38 . again , accuracies in the _ ab initio _ results of these quantities mainly suffer due to the uncertainties associated with the calculated energies of the atomic states . therefore , we calculate only the e1 matrix elements of as many as low - lying states of the considered ions employing a relativistic coupled - cluster ( rcc ) method , which is an all order perturbative method , and combine them with the experimental energy values from the national institute of science and technology ( nist ) database @xcite to determine the dominant contributions to @xmath37 . we refer this as `` main '' contribution to @xmath37 ; while the smaller contributions coming from the high - lying excited states are estimated in the _ ab initio _ formalism using the dirac - hartree - fock ( dhf ) method and are mentioned as `` tail '' contribution to @xmath37 . to estimate the other two contributions , it is not possible to use sum - over - states approach , so we determine @xmath38 in the random - phase approximation ( rpa ) . this included core - polarization effects to all orders . it has been found that rpa can give these values reliably for the inert gas configured atomic systems @xcite . again as demonstrated later , the @xmath40 contributions are very small in these ions . thus , we evaluate them using the dhf method . a small number of e1 matrix elements of the @xmath136 transitions of @xmath57ba@xmath5 are borrowed from the work of sahoo _ @xcite , while the rest e1 matrix elements for the evaluation of `` main '' contribution to @xmath137 are obtained considering the singles and doubles excitation approximation in the rcc ( sd ) method as described in refs . @xcite . in the sd method , the wave function of the state with the closed - core with a valence electron @xmath138 is represented as an expansion @xmath139 |\phi_v\rangle,\nonumber \\ & & \label{expansion}\end{aligned}\ ] ] where @xmath140 is the dhf wave function of the state . in the above expression , @xmath141 and @xmath142 are the creation and annihilation operators with the indices @xmath143 and @xmath144 designating the virtual and core orbitals of @xmath140 , @xmath145 and @xmath146 are the corresponding single core and valence excitation coefficients , and @xmath147 and @xmath148 are the double core and valence excitation coefficients . to obtain the dhf wave function , we use a finite size basis set consisting of 70 b - splines constrained to a large cavity of radius r = @xmath149 a.u . and solved self consistently using the roothan equation on a nonlinear grid . lccccccccccccccccc & & & & & & & + resonances & @xmath106 & @xmath0 & @xmath107 & @xmath0 & @xmath107 & @xmath0 & @xmath107 & @xmath0 & @xmath107 & @xmath0 & @xmath107 & @xmath0 & @xmath107 + + @xmath14ca@xmath5 & + @xmath108 & 393.366 + & & 394.64(2 ) & @xmath150 & 394.64(3 ) & @xmath151 & 394.64(2 ) & 1.0 & 394.63(4 ) & 6.33 & 394.63(3 ) & 17.0 & 394.63(3 ) & 22.39 + @xmath111 & 396.847 & + @xmath152 & 854.209 + & & - & - & 1150.39(2 ) & 85.95 & 975.6(4 ) & 90.54 & 891.4(3 ) & 94.09 & -&-&-&- + @xmath2sr@xmath5 & + @xmath114 & 407.7714 + & & 412.5(3 ) & @xmath153 & 412.46(2 ) & @xmath154 & 412.42(4 ) & 6.98 & 412.38(4 ) & 24.16 & 412.35(3 ) & 37.15 & 412.31(3 ) & 54.61 + @xmath116 & 421.5524 & + @xmath155 & 1032.7309 & + & & - & - & - & - & 1379.4(3 ) & 100.44 & 1130.8(4 ) & 105.46 & - & - & - & - + @xmath57ba@xmath5 & + @xmath119 & 455.4033 + & & 469.1(5 ) & @xmath156 & 468.5(1 ) & @xmath157 & 467.9(4 ) & @xmath158 & 467.6(4 ) & 29.01 & 467.3(1 ) & 53.75 & 467.1(1 ) & 70.27 + @xmath122 & 493.4077 & + @xmath159 & 614.1713 + & & 810.1(8 ) & 189.71 & 691(2 ) & 237.75 & 644.7(5 ) & 275.99 & 623.3(5 ) & 302.79 & - & - & - & - + + lccccccccccccccccc & & & & & & & + resonances & @xmath106 & @xmath0 & @xmath107 & @xmath0 & @xmath107 & @xmath0 & @xmath107 & @xmath0 & @xmath107 & @xmath0 & @xmath107 & @xmath0 & @xmath107 + + @xmath14ca@xmath5 & + @xmath111 & 396.847 & + @xmath152 & 854.209 + & & - & - & 1173.5(2 ) & 85.12 & 982.7(2 ) & 89.77 & 893.4(3 ) & 93.37 & -&-&-&- + @xmath2sr@xmath5 & + @xmath114 & 407.7714 + & & 416.93(4 ) & @xmath160 & 416.88(3 ) & @xmath161 & 416.85(4 ) & 7.66 & 416.81(4 ) & 23.82 & 416.77(1 ) & 38.63 & 416.74(3 ) & 52.53 + @xmath116 & 421.5524 & + & & 442.49(4 ) & @xmath162 & 442.36(3 ) & @xmath163 & 442.25(3 ) & 6.12 & 442.13(4 ) & 22.84 & 442.03(8 ) & 38.18 & 441.93(3 ) & 52.07 + & & 477.99(5 ) & @xmath164 & 478.85(1 ) & @xmath165 & 479.32(7 ) & 3.55 & 479.98(9 ) & 21.77 & 480.65(1 ) & 37.83 & 481.28(7 ) & 51.73 + @xmath155 & 1032.7309 & + & & - & - & - & - & 1391.4(3 ) & 98.46 & 1134.5(4 ) & 102.92 & - & - & - & - + @xmath57ba@xmath5 & + @xmath119 & 455.4033 + & & 479.5(2 ) & @xmath166 & 478.9(2 ) & @xmath167 & 478.4(2 ) & @xmath168 & 477.9(4 ) & 27.52 & 477.6(4 ) & 53.33 & 477.4(7 ) & 69.73 + @xmath122 & 493.4077 & + & & 505.5(2 ) & @xmath169 & 505.3(4 ) & @xmath170 & 505.04(41 ) & @xmath171 & 504.8(4 ) & 25.56 & 504.76(4 ) & 52.23 & 504.69(7 ) & 68.53 + & & 568.8(2 ) & @xmath172 & 572.14(2 ) & @xmath173 & 576.52(2 ) & @xmath174 & 582.4(2 ) & @xmath175 & 589.7(4 ) & 50.45 & 591.7(2 ) & 65.99 + @xmath159 & 614.1713 + & & 894.3(8 ) & 153.62 & 729.9(2 ) & 173.67 & 665.9(3 ) & 180.26 & 632.6(5 ) & 171.84 & - & - & - & - + + in order to verify contributions from the higher level excitations , we also estimate leading order contributions from the triple excitations perturbatively in the sd method framework ( sdpt method ) by expressing the atomic wave functions as @xcite @xmath176 where @xmath177 is the perturbed triple valence excitation amplitudes . after obtaining wave functions employing the sd and sdpt method , we determine the e1 matrix element for a given transition between the states @xmath178 and @xmath179 by evaluating the expression @xmath180 lccccccc + & & & + @xmath181 @xmath182,@xmath183 @xmath184,@xmath185 & @xmath0 & @xmath186 & @xmath181 @xmath70,@xmath183 @xmath184,@xmath185 & @xmath0 & @xmath186 + @xmath1813,0 @xmath187 & 395.79(2 ) & 8.69 & @xmath1813,0@xmath1881,0@xmath189 & 395.79(3 ) & 3.35 + & 852.5(2 ) & 95.86 & & 992(4 ) & 89.71 + & 999(4 ) & 89.46 & @xmath1813,0@xmath1882,0@xmath189 & 395.79(3 ) & 3.35 + @xmath1813,0@xmath1883,0@xmath189 & 395.79(2 ) & 3.35 & & 1077(9 ) & 87.31 + & 851.3(2 ) & 95.95 & @xmath1813,0@xmath1883,0@xmath189 & 395.79(3 ) & 3.35 + & 1089(7 ) & 87.02 & & 1064(9 ) & 87.61 + @xmath1813,0@xmath1884,0@xmath189 & 395.79(4 ) & 3.35 & @xmath1813,0@xmath1884,0@xmath189 & 395.78(3 ) & 3.35 + & 851.7(2 ) & 95.92 & & 1032(7 ) & 88.48 + & 1049(4 ) & 87.99 & @xmath1813,0@xmath1885,0@xmath189 & 395.79(3 ) & 3.35 + @xmath1813,0@xmath1885,0@xmath189 & 395.79(2 ) & 8.69 & & 992(4 ) & 89.71 + & 853.4(2 ) & 95.82 & @xmath1814,0@xmath189 @xmath190 @xmath1816,0@xmath189 & 395.79(3 ) & 8.69 + & 970(3 ) & 90.44 & & 949(3 ) & 91.21 + + + & & & + @xmath181f,@xmath191 @xmath190 @xmath192,@xmath185 & @xmath0 & @xmath186 & @xmath181f,@xmath191 @xmath190 @xmath192,@xmath185 & @xmath0 & @xmath186 + @xmath1814,0@xmath189 @xmath190 @xmath1813,0@xmath189 & 416.99(8 ) & 14.79 & @xmath1814,0@xmath189 @xmath190 @xmath1813,0@xmath189 & 416.99(8 ) & 13.72 + & 1017.4(3 ) & 108.24 & @xmath1814,0@xmath189 @xmath190 @xmath1814,0@xmath189 & 416.99(7 ) & 13.72 + & 1534(30 ) & 97.96 & @xmath1814,0@xmath189 @xmath190 @xmath1815,0@xmath189 & 416.99(8 ) & 14.14 + @xmath1814,0@xmath189 @xmath190 @xmath1814,0@xmath189 & 416.99(8 ) & 13.87 & @xmath1814,0@xmath189 @xmath190 @xmath1816,0@xmath189 & 416.99(8 ) & 14.56 + & 1010.7(5 ) & 108.52 & & 1486(32 ) & 98.45 + @xmath1814,0@xmath189 @xmath190 @xmath1815,0@xmath189 & 416.99(7 ) & 14.15 & @xmath1815,0@xmath189 @xmath190 @xmath1817,0@xmath189 & 416(3 ) & 14.56 + & 1012.4(6 ) & 108.45 & & 1301(14 ) & 100.88 + @xmath1814,0@xmath189 @xmath190 @xmath1816,0@xmath189 & 416.99(7 ) & 14.99 + & 1020.6(2 ) & 108.12 + & 1429(20 ) & 99.08 + + + & & & + @xmath181 @xmath182,@xmath183 @xmath184,@xmath185 & @xmath0 & @xmath186 & @xmath181 @xmath70,@xmath183 @xmath184,@xmath185 & @xmath0 & @xmath186 + @xmath1811,0@xmath1880,0@xmath193 & 480.6(7 ) & @xmath194 & @xmath1811,0@xmath1881,0@xmath189 & 480.53(3 ) & 5.36 + & 588.3(2 ) & 329.33 & & 641.2(5 ) & 256.97 + & 695.7(9 ) & 219.39 + @xmath1811,0@xmath1881,0@xmath189 & 480.7(4 ) & @xmath195 & @xmath1811,0@xmath1882,0@xmath189 & 480.58(4 ) & 0.91 + & 587.3(3 ) & 331.55 & & 647.8(6 ) & 251.11 + & 720.47(2 ) & 207.98 + @xmath1811,0@xmath1882,0@xmath189 & 480.68(4 ) & @xmath196 & @xmath1811,0@xmath1883,0@xmath189 & 480.55(4 ) & 3.39 + & 588.3(5 ) & 329.33 & & 644.1(5 ) & 254.42 + & 695.7(5 ) & 219.40 + @xmath1811,0@xmath1883,0@xmath189 & 480.56(4 ) & 3.55 & @xmath1812,0 @xmath1884,0@xmath189 & 480.56(5 ) & 7.84 + & 589.7(4 ) & 329.62 & & 637.7(3 ) & 260.25 + & 675.4(5 ) & 231.02 + to find out the uncertainties with the calculated e1 matrix elements , we have carried out semi - empirical scaling of the wave functions that accounts for evaluation of missing correlations contributions to the wave functions from the approximated sd and sdpt methods . this procedure involves scaling of the excitation coefficients and reevaluation of the e1 matrix elements . the scaling factors are decided from the correlation energy trends in the sd and sdpt methods . details regarding this scaling procedure are given in ref . @xcite . and @xmath197 states of @xmath14ca@xmath5 with @xmath198.,width=321,height=226 ] .[tuneoutj ] the @xmath58 values ( in nm ) for all possible magnetic sublevels @xmath199 of the @xmath14ca@xmath5,@xmath2sr@xmath5 and @xmath57ba@xmath5 alkaline earth - metal ions using circularly polarized light . [ cols="<,^,^,<,^,^,<,^,^ " , ] * @xmath14ca@xmath5 : * as evident from fig . ( [ casd ] ) , the dynamic polarizabilities for the @xmath200 state are small except in the vicinity of the resonant @xmath200-@xmath21 and @xmath200-@xmath23 transitions around 396.847 nm and 393.366 nm respectively . since the @xmath197 states have significant contributions from the resonances in the interested wavelength range , the @xmath0 are expected to lie in between these resonances . we found a total of nine @xmath0 for all possible magnetic sublevels of the @xmath200-@xmath201 transition in between four resonances . the first four @xmath0 are located around 395 nm between the resonant @xmath200-@xmath21 and @xmath200-@xmath23 transitions for all the @xmath199 magnetic sublevels of the @xmath202 state . out of these , two @xmath0 support blue - detuned trap , whereas the other two support red - detuned trap . the next five @xmath0 are identified at 850.9(2 ) nm , 853.1(2 ) nm , 1467.8(4 ) nm , 1013.4(5 ) nm and 870.7(3 ) nm , which lie in the infrared region . for some of the @xmath199 sublevels , the @xmath0 is missing . in such case , it would be imperative to consider a geometry where @xmath0 will be independent of the magnetic sublevels as mention in sec . [ introsec ] and discussed elaborately in our previous work @xcite . in table [ magicd521 ] , we present the @xmath0 for the @xmath203 transition considering all the magnetic sublevels of the @xmath204 state . as seen , most of these @xmath0 in the @xmath14ca@xmath5 ion support red detuned trap , indicated by small positive values of the polarizabilities for the corresponding @xmath0 values . similarly , we tabulate @xmath0 for the @xmath205 ( @xmath81 = @xmath206 ) - @xmath207 transition in table [ magicd322 ] and [ magicd522 ] . it can be evidently seen from the table that @xmath0 are red shifted from the @xmath0 for @xmath205 ( @xmath208 ) - @xmath207 . similarly in table [ magicca ] , we list the @xmath0 values between 300 - 1300 nm for the @xmath209 transitions . the @xmath70-dependent polarizabilities values at the respective @xmath0 are listed as well . for this wavelength range , total twenty four @xmath0 are located . out of which , fourteen @xmath0 are identified in the infrared region . from this table , it can be found that for the @xmath210 transitions , all @xmath0 support red - detuned traps . and @xmath211 states of @xmath2sr@xmath5 with @xmath212.,width=321,height=226 ] * @xmath2sr@xmath5 : * the dynamic polarizabilities for the @xmath213 , @xmath202 and @xmath214 states of @xmath2sr@xmath5 calculated by us are plotted in fig . ( [ srsd ] ) . a number of @xmath0 are identified by the intersections of the polarizability curves of the @xmath213 and @xmath211 states for all their magnetic sublevels of the @xmath211 states in the @xmath215 transitions and are presented in table [ magicd321 ] along with their resonant lines . four @xmath0 are found to be around 413 nm between the @xmath213-@xmath24 and @xmath213-@xmath31 , resonant transitions . these values belong to the visible region , while the other five @xmath0 are located at 1009.3(3 ) nm , 1019.7(3 ) nm , 1062.5(3 ) nm and 1577.2(3 ) nm that lie in the infrared region . all the @xmath0 values mentioned for the @xmath213-@xmath202 transition , except the one at 412.5(9 ) nm , support the red - detuned trapping scheme . similarly , for the @xmath213-@xmath214 transition total eight @xmath0 are appearing for all possible @xmath199 sublevels . among them two @xmath0 are located at 1379.4(3 ) nm and 1130.8(4 ) nm appear after the @xmath214-@xmath31 resonance for the @xmath199=1/2 and @xmath199=@xmath206 magnetic sublevels respectively . use of these @xmath0 are recommended to carry out experiments selectively for the corresponding magnetic sublevels . similarly , we present @xmath0 for the @xmath216 ( @xmath81 = @xmath206 ) - @xmath217 transition in table [ magicd322 ] and [ magicd522 ] . it can be noticed from these tables that @xmath0 are red shifted from the @xmath0 for @xmath216 ( @xmath208 ) - @xmath217 transition . we have also determined total sixteen extra @xmath0 between @xmath213-@xmath24 and @xmath202-@xmath31 resonance transition . in table [ magicca ] , @xmath0 values above 300 nm are listed in the case of @xmath2sr@xmath5 for the @xmath218 transitions . it is found that @xmath0 around 417 nm with very small polarizabilities for the @xmath219 and @xmath220 transitions . therefore , it will be challenging to trap the @xmath2sr@xmath5 ion at these wavelengths . however , the @xmath0 values in the infrared region for these transitions may be useful for trapping the above ion in the experiments . and @xmath221 states of @xmath57ba@xmath5 with @xmath198.,width=321,height=226 ] * @xmath57ba@xmath5 : * total nine @xmath0 are found for the @xmath222-@xmath223 transition of @xmath57ba@xmath5 , among which four @xmath0 are around 468 nm in the vicinity of the @xmath222-@xmath47 resonant transition . the next @xmath0 at 587.6(9 ) nm , 589.5(3 ) nm and 589.6(5 ) nm are located at the sharp intersection of polarizability curves close to the @xmath223-@xmath47 and @xmath223-@xmath43 resonances , as seen in fig . ( [ ba1 ] ) . the last two @xmath0 are located at 841.7(5 ) nm and 690.7(7 ) nm for the @xmath199=@xmath224 and @xmath225 sublevel respectively , have positive polarizabilities . hence these @xmath0 could provide sufficient trap depth at the reasonable laser power . in fact , some of the expected @xmath0 are missing for the @xmath199= @xmath226 and @xmath206 sublevels . similarly , several @xmath0 are also located for the @xmath222-@xmath227 transitions , as seen from fig . ( [ ba1 ] ) , in the wavelength range 300 - 800 nm which are listed in table [ magicd521 ] . the expected trend of locating @xmath0 between the resonances in this transition is similar to the previous two ions . for the @xmath228 ( @xmath229 ) - @xmath230 transition , we list the @xmath0 in table [ magicd322 ] and [ magicd522 ] . these magic wavelengths are slightly red shifted to those demonstrated for @xmath228 ( @xmath229 ) - @xmath230 transition . we also found total fifteen @xmath0 between @xmath222-@xmath43 and @xmath223-@xmath43 resonance transitions in both the tables . we have also determined an extra @xmath0 at 590.5 nm in table [ magicd322 ] , which supports a red detuned trap . in table [ magicca ] , we also list @xmath0 for the @xmath231 transitions which lie within the wavelength range of 300 - 800 nm . we correspondingly locate twenty @xmath0 in the visible region . we notice that all the @xmath0 values , except around 480 nm , are expected to be more promising for experiments . an ion trap at these wavelengths can have sufficient trap depth at the reasonable laser power . dependent dynamic dipole polarizabilities ( in a.u . ) for the @xmath232 ( @xmath233 3 , 4 ) and @xmath234 @xmath235 states of @xmath14ca@xmath5 with @xmath212.,width=321,height=226 ] dependent dynamic dipole polarizabilities ( in a.u . ) for the @xmath236 ( @xmath70= 4 , 5 ) and @xmath237 @xmath238 states of @xmath2sr@xmath5 with @xmath212.,width=321,height=226 ] dependent dynamic dipole polarizabilities ( in a.u . ) for the @xmath239 ( @xmath70 = 1 , 2 ) and @xmath240 @xmath238 states of @xmath57ba@xmath5 with @xmath212.,width=321,height=226 ] * tune - out wavelengths : * table [ tuneoutj ] and [ tuneoutf ] illustrate the identified tune out wavelengths of the @xmath241 , @xmath132 and @xmath133 states in the @xmath242 and @xmath243 levels of the @xmath14ca@xmath5 , @xmath2sr@xmath5 and @xmath57ba@xmath5 alkaline earth metal ions . to locate these tune out wavelengths , we have calculated the dynamic polarizabilities of the above states for a particular range of wavelength in the vicinity of relevant resonances for the corresponding ion and find out values of @xmath244 for which the polarizability values tend to zero . we have also used our the frequency dependent scalar polarizability results of the @xmath14ca@xmath5 , @xmath2sr@xmath5 and @xmath57ba@xmath5 ions to find out @xmath0 that are independent of the magnetic sublevels @xmath81 of the atomic states ; so also hyperfine sublevel independent . table [ magicsd ] lists of the @xmath0 values for the @xmath241-@xmath245 transitions , which lie within the wavelength range of 300 - 1500 nm . we are also able to locate the tune out wavelengths of the ground , @xmath132 and @xmath133 states of the considered alkaline ions that are independent of the @xmath70 , @xmath246 and @xmath199 values of the respective ion and given them in table [ tunesd ] . occurrences of these @xmath0 and @xmath247 for the considered ions can offer pathways to carry out many high precision measurements with minimal systematics .

, phys . we also present values explicitly at the 1064 nm for the atomic states associated with the clock transitions which may be useful for creating `` high - field seeking '' traps for the above ions using the nd : yag laser . the tune out wavelengths at which the states would be free from the stark shifts are also presented .

we present additional magic wavelengths ( ) for the clock transitions in the alkaline - earth metal ions considering circular polarized light aside from our previously reported values in [ j. kaur et al . , phys . rev . a * 92 * , 031402(r ) ( 2015 ) ] for the linearly polarized light . contributions from the vector component to the dynamic dipole polarizabilities ( ) of the atomic states associated with the clock transitions play major roles in the evaluation of these , hence facilitating in choosing circular polarization of lasers in the experiments . moreover , the actual clock transitions in these ions are carried out among the hyperfine levels . the values in these hyperfine transitions are estimated and found to be different from for the atomic transitions due to different contributions coming from the vector and tensor part of . importantly , we also present values that depend only on the scalar component of for their uses in a specially designed trap geometry for these ions so that they can be used unambiguously among any hyperfine levels of the atomic states of the clock transitions . we also present values explicitly at the 1064 nm for the atomic states associated with the clock transitions which may be useful for creating `` high - field seeking '' traps for the above ions using the nd : yag laser . the tune out wavelengths at which the states would be free from the stark shifts are also presented . accurate values of the electric dipole matrix elements required for these studies are given and trends of electron correlation effects in determining them are also highlighted .

0906.3735

i

this article has two purposes . the first one is to present a new implementation of dynamical mean - field theory ( dmft ) within electronic structure calculation methods . this implementation is based on a highly precise full - potential linear augmented plane wave method ( flapw ) , as implemented in the wien2k electronic structure code @xcite . the second purpose of this article is to report on dmft calculations for the iron oxypnictide lafeaso , the parent compound of the ` @xmath3'-family of recently discovered iron - based superconductors . the strength of electronic correlations in these materials is an important issue , which has been a subject of debate in the literature @xcite . the combination of dynamical mean - field theory with density - functional theory in the local density approximation ( lda+dmft ) provides a powerful framework for the quantitative description of electronic correlations in a realistic setting . a number of materials have been investigated in this framework over the past decade , such as transition metals and transition - metal oxides , rare - earth and actinide compounds , and organic conductors . these examples testify to the progress in our understanding of the key physical phenomena associated with the competition between the localized and itinerant characters of electrons belonging to different orbitals ( see e.g. refs . [ ] for reviews ) . in the past few years , a new generation of lda+dmft implementations have been put forward @xcite , which emphasize the use of wannier functions as a natural bridge between the band - structure and the real - space description of the solid in terms of orbitals . these functions span the subset of orbitals which are treated within the many - body dmft framework . in this article , we present an implementation of lda+dmft within the full potential linear augmented plane wave ( flapw ) framework , using atomic orbitals that are promoted to wannier functions by a truncated expansion over bloch functions followed by an orthonormalization procedure . this is a simpler alternative to the previous implementation of dmft within flapw @xcite , which constructed the wannier functions following the prescription of maximal localisation @xcite . the choice of flapw is motivated by the high level of accuracy of this all - electron , full - potential method . in the present work , we use the wien2k electronic structure package @xcite , and we have constructed an interface to it that allows for the construction of wannier - like functions used in dmft . our implementation is described in detail in sec . [ sect : theory ] . as a benchmark , we perform calculations on a test material , srvo@xmath4 , which are presented in appendix [ sect : srvo3 ] and compared to previously published results for this material @xcite . throughout this article , many - body effects are treated in the dmft framework using the recently developed continuous - time strong - coupling quantum monte carlo algorithm of p.werner and coworkers @xcite . because very low temperatures can be reached , and very high accuracy can be obtained at low - frequency , this algorithm represents a major computational advance in the field . in sec . [ sect : results ] , we address the issue of electronic correlations in lafeaso . the dmft calculations which have been published soon after the experimental discovery of superconductivity in the iron oxypnictides have provided seemingly contradictory answers to this question . in refs . [ ] , k. haule and g. kotliar proposed that lafeaso is a strongly correlated metal , rather close to the mott metal - insulator transition , and characterized by a reduced value of the quasiparticle coherence scale , resulting in bad metallic behavior . in contrast , in refs . [ ] , v.anisimov and coworkers proposed that these materials are in a weak to intermediate regime of correlations . our lda+dmft calculations for lafeaso support the physical picture of a metal with intermediate correlations . the average value of the mass renormalization of the fe 3@xmath0 bands is about @xmath1 , in reasonable agreement with the picture inferred from photoemission experiments . we also find that there is no technical inconsistency between different dmft results reported for lafeaso before . we show that the discrepancies in the literature are due to two causes : i ) the specific value of the interaction parameters used in these calculations and ii ) the degree of localization of the wannier orbitals chosen to represent the fe 3@xmath0 states , to which many - body terms are applied . in sec . [ sect : results ] , we perform detailed comparisons between lda+dmft calculations performed with different degree of localization of the correlated orbitals , associated with different choices of energy windows for the wannier construction ( and accordingly , different degrees of screening of the interaction parameters ) . we point out several difficulties associated with the use of more extended wannier functions associated with the low - energy iron bands only . some of these issues have important physical consequences , in particular regarding the sensitivity to the hund s coupling . this article ends with several appendices , reporting on more detailed aspects or technical issues . appendix a is devoted to a benchmark of our implementation on a `` classical '' test compound , srvo@xmath4 . appendix b details some technical issues associated with the projection scheme used to display partial spectral functions with a given orbital character . appendix c discusses the influence of spin - flip and pair - hopping terms on the degree of correlations , on the basis of model calculations . we conclude that while these terms are indeed important close to the mott transition , they can safely be neglected in the regime of correlations relevant to lafeaso .

our findings support the physical picture of a metal with intermediate correlations . the average value of the mass renormalization of the fe 3 bands is about , in reasonable agreement with the picture inferred from photoemission experiments . the discrepancies between different lda+dmft calculations ( all technically correct ) which have been reported in the literature are shown to have two causes : i ) the specific value of the interaction parameters used in these calculations and ii ) the degree of localization of the wannier orbitals chosen to represent the fe 3 states , to which many - body terms are applied . some of these issues have important physical consequences , regarding in particular the sensitivity to the hund s coupling .

we present an approach that combines the local density approximation ( lda ) and the dynamical mean - field theory ( dmft ) in the framework of the full - potential linear augmented plane waves ( flapw ) method . wannier - like functions for the correlated shell are constructed by projecting local orbitals onto a set of bloch eigenstates located within a certain energy window . the screened coulomb interaction and hund s coupling are calculated from a first - principle constrained rpa scheme . we apply this lda+dmft implementation , in conjunction with a continuous - time quantum monte - carlo algorithm , to the study of electronic correlations in lafeaso . our findings support the physical picture of a metal with intermediate correlations . the average value of the mass renormalization of the fe 3 bands is about , in reasonable agreement with the picture inferred from photoemission experiments . the discrepancies between different lda+dmft calculations ( all technically correct ) which have been reported in the literature are shown to have two causes : i ) the specific value of the interaction parameters used in these calculations and ii ) the degree of localization of the wannier orbitals chosen to represent the fe 3 states , to which many - body terms are applied . the latter is a fundamental issue in the application of many - body calculations , such as dmft , in a realistic setting . we provide strong evidence that the dmft approximation is more accurate and more straightforward to implement when well - localized orbitals are constructed from a large energy window encompassing fe-3 , as-4 and o-2 , and point out several difficulties associated with the use of extended wannier functions associated with the low - energy iron bands . some of these issues have important physical consequences , regarding in particular the sensitivity to the hund s coupling .

0906.3735

c

in the first part of this work , we present an implementation of lda+dmft in the framework of the full - potential linearized augmented plane waves method . we formulate the dmft local impurity problem in the basis of wannier orbitals , while the full lattice green s function is written in the basis of bloch eigenstates of the kohn - sham problem . in order to construct the wannier orbitals for a given correlated shell we choose a set of local orbitals , which are then expanded onto the ks eigenstates lying within a certain energy window . in practice , we employ the radial solutions of the schrdinger equation for a given shell evaluated at the corresponding linearization energy as local orbitals . by orthonormalizing the obtained set of basis functions we construct a set of true wannier orbitals as well as projector operator matrices relating the bloch and wannier basis sets . we derive explicit formulas for the projected operator matrices in a general flapw framework , which may include different types of augmented plain waves , @xmath62 and @xmath67 orbitals . our new implementation is benchmarked using the test case of srvo@xmath4 , for which we have obtained spectral and electronic properties in very good agreement with results of previous lda+dmft calculations . in the second part of this paper we apply this lda+dmft technique to lafeaso in order to assess the degree of electronic correlations in this compound and clarify the ongoing controversy about this issue in the literature . we solved the dmft quantum impurity problem using a continuous - time quantum monte carlo approach . the wannier functions are constructed using an energy window comprising fe 3@xmath0 , as 4@xmath2 and o 2@xmath2 . the resulting wannier orbitals are rather well localized and isotropic . we take the average values of @xmath1992.69 ev and @xmath2000.79 from constrained rpa calculations , where the wannier functions and screening channels are consistent with our setting of the lda+dmft scheme . we have checked the robustness of these results by increasing the size of the energy window , what resulted in a very similar physical picture . our lda+dmft results indicate that lafeaso is a moderately correlated metal with an average value for the mass renormalization of the fe 3@xmath0 bands about 1.6 . this value is in reasonable agreement with estimates from photoemission experiments . we also consider a smaller energy window that includes fe-@xmath0 states only . the resulting wannier functions in this case are quite extended , leading to anisotropic and non - local coulomb interactions . we take different values for @xmath111 and @xmath114 , including the ones used in previous theoretical lda+dmft approaches . we demonstrate that different physical pictures ranging from a strongly correlated compound on the verge of the metal insulator transition to a moderately to weakly correlated one can emerge depending , in particular , on the choice of the hund s rule coupling @xmath114 as observed in ref . . however , there are conceptual difficulties when constructing a local hamiltonian from rather delocalized wannier orbitals . the interactions are very anisotropic and orbital dependent , and non - local interactions could also become important . in summary , we demonstrate that the discrepancies in the results of several recent theoretical works employing the lda+dmft approach stem from two main causes : i ) the choice of parameters of the local coulomb interaction on the fe 3@xmath0 shell and ii ) the degree of localization of the wannier orbitals chosen to represent the fe 3@xmath0 states , to which many - body terms are applied . regarding the first point , the calculated interaction parameters employed in the present work are significantly smaller than the values hypothesized in refs . [ ] . regarding the second point , we provide strong evidence that the dmft approximation is more accurate and more straightforward to implement when well - localized orbitals are constructed from a large energy window encompassing fe-3@xmath0 , as-4@xmath2 and o-2@xmath2 . this issue has fundamental implications for many - body calculations , such as dmft , in a realistic setting .

we present an approach that combines the local density approximation ( lda ) and the dynamical mean - field theory ( dmft ) in the framework of the full - potential linear augmented plane waves ( flapw ) method . wannier - like functions for the correlated shell are constructed by projecting local orbitals onto a set of bloch eigenstates located within a certain energy window . the screened coulomb interaction and hund s coupling we apply this lda+dmft implementation , in conjunction with a continuous - time quantum monte - carlo algorithm , to the study of electronic correlations in lafeaso . the latter is a fundamental issue in the application of many - body calculations , such as dmft , in a realistic setting . we provide strong evidence that the dmft approximation is more accurate and more straightforward to implement when well - localized orbitals are constructed from a large energy window encompassing fe-3 , as-4 and o-2 , and point out several difficulties associated with the use of extended wannier functions associated with the low - energy iron bands .

we present an approach that combines the local density approximation ( lda ) and the dynamical mean - field theory ( dmft ) in the framework of the full - potential linear augmented plane waves ( flapw ) method . wannier - like functions for the correlated shell are constructed by projecting local orbitals onto a set of bloch eigenstates located within a certain energy window . the screened coulomb interaction and hund s coupling are calculated from a first - principle constrained rpa scheme . we apply this lda+dmft implementation , in conjunction with a continuous - time quantum monte - carlo algorithm , to the study of electronic correlations in lafeaso . our findings support the physical picture of a metal with intermediate correlations . the average value of the mass renormalization of the fe 3 bands is about , in reasonable agreement with the picture inferred from photoemission experiments . the discrepancies between different lda+dmft calculations ( all technically correct ) which have been reported in the literature are shown to have two causes : i ) the specific value of the interaction parameters used in these calculations and ii ) the degree of localization of the wannier orbitals chosen to represent the fe 3 states , to which many - body terms are applied . the latter is a fundamental issue in the application of many - body calculations , such as dmft , in a realistic setting . we provide strong evidence that the dmft approximation is more accurate and more straightforward to implement when well - localized orbitals are constructed from a large energy window encompassing fe-3 , as-4 and o-2 , and point out several difficulties associated with the use of extended wannier functions associated with the low - energy iron bands . some of these issues have important physical consequences , regarding in particular the sensitivity to the hund s coupling .

astro-ph0507041

r

we use an idl - based program to detect sources in both the acis - s and the _ xmm - newton _ pn data . as in the previous applications ( e.g. , wang et al . 2003 ; wang 2004a ) , this program , optimized to detect point - like sources , uses a combination of detection algorithms : wavelet , sliding - box , and maximum likelihood centroid fitting . first , we construct the ` mexican cap ' wavelet images on scales of 1 , 2 , 4 and 8 image bins ( bin size @xmath26@xmath16for the pn and 0.5@xmath16for the acis - s ) . on each scale we search for source candidates corresponding to local maxima with signal - to - noise ratios @xmath27 . next , we apply a map detection ( ` sliding box ' method ) with a background map produced by excising the source candidates and adaptively smoothing the map to achieve a local count - to - noise ratio greater than 10 . finally , the sources detected with the map method are analyzed by a maximum likelihood algorithm , using both the background map and an approximate gaussian psf . this analysis gives optimal source positions and their @xmath19 errors . the source detection in both the map detection and the maximum likelihood analysis is based on data within the 50% psf energy - encircled radius ( eer ) for the pn data and the 90% eer for the acis - s data . the final accepted sources all have the individual false detection probability @xmath28 ( acis - s ) and @xmath29 ( pn ) . the processed pn data still contain various residual artifacts ( more significant than in the acis - s data ) ; the chosen stringent detection threshold minimizes their effect in the source detection . the source detections are carried out in the broad ( b ) , soft ( s ) , and hard ( h ) bands , defined differently for the acis - s and pn data sets in the notes to tables 1 and 2 . for each data set , the detected sources in the three bands are merged together . multiple detections with overlapping 2@xmath30 centroid error circles are considered to be the same source , and the centroid with the smallest error is adopted . tables 1 and 2 summarize the results from our source detection in the two data sets . for ease of reference , we will refer to x - ray sources detected in the _ xmm - newton _ pn and acis data sets with the prefixes xp and xa , respectively ( e.g. , xp-13 ) . the source locations are marked in the x - ray intensity images ( figs . [ fig : sou_pn ] and [ fig : sou_acis ] ) . the detection reveals many more sources in the data than in the _ xmm - newton _ data in the overlapping region around x-1 . part of this difference is due to the limited spatial resolution of the _ xmm - newton _ instrument ; the source detection sensitivity is very much affected by the psf of x-1 and the presence of the diffuse emission , as well as source confusion . nevertheless , most bright x - ray sources in the field are also detected with the _ xmm - newton _ data . several relatively bright sources , such as xa-13 , xa-17 , and xp-49 ( the pn source next to xa-35 in fig . [ fig : sou_acis ] ) , should have been detected in both data sets . the fact that they appear only in one data set indicates their strong variability from one observation to another . we may further use the _ xmm - newton _ and data sets to provide limited x - ray spectral information on the detected sources . most of the _ xmm - newton _ detected sources are apparently outside the optical / near - ir main body of and are probably unrelated to the galaxy ( fig . [ fig : sou_pn ] ) . the detected sources , on the other hand , are more likely to be associated with the galaxy . we thus extract an accumulated acis - s spectrum of the sources located in the s3 chip , excluding sources that are located at the edges ( i.e. , xa-12 , 16 , and 23 ; fig . [ fig : sou_acis ] ) . this spectrum can be characterized ( @xmath31 ) by a power law with a photon index of 1.2(0.89 - 1.6 ) and an absorption column density @xmath32 ( fig . [ fig : spec_sou_acis ] ) . although the constraints on the spectral parameters are generally weak , the index is consistent with the value ( @xmath33 ) expected for typical high - mass x - ray binaries . the @xmath34 is considerably lower than that expected total absorption toward sources inside ; the galactic absorption alone is @xmath35 ( stark et al . the absorption - corrected luminosity of the sources is @xmath36 in the 0.3 - 8 kev band . therefore , the spectrum , especially in the low energy part , may still significantly be contaminated by galactic objects . for relatively bright sources , we give hardness ratios to constrain individual spectral properties ( tables 1 and 2 ) . most of the calculated ratios are consistent with a power law that has an index in the range of 1 - 3 , together with a foreground absorption @xmath37 . such sources are probably x - ray binaries in or background agns . soft x - ray sources , especially those with hr1 values @xmath38 ( table 1 ) , should be in our galaxy ( 4.1 ) , because the inferred @xmath34 is less than the accepted galactic absorption . most of the other sources are too faint to be constrained individually . a useful , though crude , conversion factor from a count rate ( in either table 1 or 2 ) to an absorption - corrected energy flux in the 0.5 - 8 kev band is @xmath39 @xmath40 for a source with a power law of a photon index @xmath41 and a total x - ray - absorbing gas column density of @xmath42 , reasonable approximations for sources in ( see 4.1 ) . the _ xmm - newton _ observations show a large intensity variation of x-1 , a factor of up to @xmath1 and 4 in the pn 0.5 - 2.0 kev and 2.0 - 7.5 kev bands and on a time scale of @xmath43 s ( fig . [ fig : var ] ) . this amplitude is a factor of @xmath41 greater than that during the observation @xcite . similar variability is also seen in the mos data . the large luminosity dip , as seen in the light curves , could be due to an eclipsing of the accreting compact source by its companion . we detect no apparent periodic signal ; both the fft power spectrum and the period folding analysis show too much confusion from the harmonics and their aliases of the ccd readout period ( 73.4 ms ) . [ fig : spec_x1]a shows that the _ xmm - newton _ spectra of x-1 are nearly featureless ( except for various instrumental features ) . we fit the spectra with various models that are typically used for x - ray binaries , together with a foreground photoelectric absorption . the overall metal abundance of the absorbing gas is allowed to vary , relative to hydrogen , although the relative metal abundances are fixed to the pattern of balucinska - church & mccammon ( 1992 ) . we find that a simple power law model with a best - fit @xmath44 can be ruled out with a null hypothesis probability of @xmath45 ; the spectra appear to have an intrinsically blackbody - like convex shape . but the spectra are reasonably well characterized ( @xmath46 ) by the multi - color disk model ( mcd ; i.e. , _ diskbb _ in the _ xspec _ spectral analysis software package ; arnaud 1996 ; makishima et al . the fitted inner disk temperature and radius are @xmath47 kev and @xmath48 km , where @xmath49 is the inclination angle of the disk , while the absorption column density is @xmath50 with a metal abundance @xmath51 solar ; a fit with the fixed solar metal abundances is not acceptable ( @xmath52 ) . this unusually low metal abundance is probably not physical and may be due to uncertainties in the spectral calibration at low energies . the absorption - corrected luminosity of the source is @xmath53 in the 0.3 - 8.0 kev band . both the spectral shape and the luminosity of x-1 are very similar to those of the well - studied persistent x - ray binaries with stellar mass bhs ( i.e. , lmc x-1 , lmc x-3 , and cyg x-1 ) . to further characterize the putative bh as well as the accretion disk of x-1 , we fit the _ xmm - newton _ spectra with a self - consistent comptonized mcd ( cmcd ) model ( wang et al . 2004 ; yao et al . this model is implemented in xspec as a table of spectra generated from monte - carlo simulations of the comptonization , which assumes a spherically symmetric , thermal corona around an accretion disk . the fitted parameters of the cmcd model are the corona optical depth @xmath54 , effective radius @xmath55 km , electron temperature @xmath56 kev , and disk inclination angle @xmath57 , as well as @xmath58 kev and @xmath59 km . the obtained @xmath34 is almost the same as that obtained for the mcd model . the fit is satisfactory ( @xmath60 ) . following wang et al . ( 2004 ) , we further infer the mass of the bh by assuming that @xmath61 represents the radius of the last stable circular orbit , after correcting for various general relativity spectral hardening and doppler shift effects ( a factor of @xmath41 total correction ) . for a non - spinning bh , our inferred mass is 4.1(3.1 , 4.9 ) m@xmath5 , which depends weakly on @xmath49 ( within its 90% uncertainty range ) . but for an extreme spinning bh , the mass could be a factor of up to 6 greater , sensitively depending on @xmath49 ( see fig . 2 in wang et al . 2004 ) . there is a marginal presence of an emission line at @xmath62 kev , presumably representing the k@xmath13 transition of neutral or weakly ionized iron . the inclusion of a narrow gaussian line with the centroid fixed at this energy leads to a small improvement of the fit ( @xmath63 ) and does not significantly change the parameters of the other spectral components . the luminosity of the line is @xmath64 , corresponding to an equivalent width of @xmath65 ev . to test the spectral variability , we further extract two separate sets of spectra in the time intervals less and greater than 8000 s in fig . [ fig : var ] . however , the total of pn+mos counts in the lower flux interval is only about 470 . the two spectra show no statistically significant difference . for comparison with the _ xmm - newton _ spectra , we further extract a acis - s spectrum of x-1 from a circle of 8@xmath16radius and a local background spectrum from a concentric annulus of radius 32@xmath16 - 67@xmath16 . we use the newly improved ciao routine _ mkacisrmf _ to generate the spectral response matrices and include davis s model for the pile - up correction ( davis 2001 ) . our obtained pile - up fraction is similar to that found in bauer & brandt ( 2004 , who use a different method entirely ) . the same cmcd model without any parameter adjustment gives an acceptable fit to this acis - s spectrum of x-1 ( @xmath66 ) ; there is only a slight excess of the observed soft x - ray flux above the model . simply letting one parameter free [ e.g. , @xmath67 improves the fit [ @xmath68 ; f - test probability for no improvement is @xmath69 ; fig . [ fig : spec_x1]b ] . the inferred 0.3 - 8 kev luminosity is almost exactly the same as the mean value during the _ xmm - newton _ observation . therefore , there is no substantial difference in both the spectral shape and luminosity between the _ xmm - newton _ and spectra of x-1 . [ fig : spec_x1]b shows little evidence for residual , emission line - like features that are apparently present in the x-1 spectrum extracted by @xcite , at somewhat unexpected energies ( e.g. , @xmath70 and 3.65 kev ; their fig . 4 and discussion ) . therefore , these features of the spectra are likely data processing artifacts . there are clear indications for the presence of diffuse soft x - ray emission from . fig . [ fig : xc_c ] shows the large - scale soft x - ray intensity distribution of the field . the distribution is calculated after a subtraction of the blank - sky background , which is normalized to the local source - removed intensity estimated in an annulus of off - axis radius @xmath71 in the pn observation . in this step , we can approximately account for the background variation from one observation to another , particularly important for because of its low galactic latitude position . the soft x - ray structure near x-1 can only be examined in the high resolution observation ( fig . [ fig : acis_xc_c ] ; see also @xcite ) . to quantify the diffuse soft x - ray component , one needs to excise the detected sources and to estimate their residual contamination as well as sources below our detection limit . with the limited spatial resolution of the _ xmm - newton _ data , a clean separation of the sources from the diffuse component is difficult . one might use a large eer to exclude a large fraction of source counts . however , the 90% eer at 1.5 kev , for example , is @xmath72@xmath16on - axis and increases to @xmath73@xmath16at an off - axis angle of 12@xmath74 . the adoption of such an eer for all the sources would leave regions too sparse for a diffuse emission study . a smaller eer is adequate for the bulk of faint sources ( cr @xmath75 ) , which would leave acceptable amounts of contamination . for such a source , our adopted removal radius is twice the source detection radius for both the acis - s and pn data ( or @xmath76 psf eer for the pn data ) . for brighter sources , we scale this radius by a factor of @xmath77 . the adopted source removal regions are outlined in figs . [ fig : sou_pn ] and [ fig : sou_acis ] . of course , the remaining `` diffuse '' enhancement is still contaminated by the psf wing of x-1 and other discrete sources . the on - axis pn psf can be characterized by a king function , @xmath78^{-\alpha},\ ] ] where @xmath79 is the off - source angular distance and @xmath80 is a normalization factor , while the core radius @xmath81 or 52 and index @xmath82 or 1.5 for the the 0.5 - 2 kev or 2 - 4.5 kev bands , respectively . we compare the psf with the radial profiles of the source - removed pn intensity around x-1 by fitting the normalization and local uniform background ( fig . [ fig : x1_rbp ] ) . the psf gives a reasonably good fit to the profile in the 2 - 4.5 kev band ( @xmath83 ) . however , the fit in the 0.5 - 2 kev band is not acceptable ( @xmath84 ) ; an excess of the observed intensity above the psf is apparent at the annulus of the off - source distance between @xmath85 . the total net cr in this annulus is @xmath86 ( 0.005 ) @xmath87 in the 0.5 - 2 kev ( 2 - 4.5 kev ) band . we estimate that @xmath88 in the 0.5 - 2 kev band is due to the residual point - like contribution , assuming that it dominates the 2 - 4.5 kev band cr and has a mean spectrum similar to the best - fit absorbed power law of the detected sources ( 3.1 ) . the remaining @xmath89 in the 0.5 - 2 kev band may be a truly diffuse component . the luminosity of contribution is about the same as that of the detected sources within , excluding x-1 ( 3.1 ) . the faint point source contribution is probably a bit overestimated here , if it is less contaminated by the galactic stellar population ( which tends to contribute more soft x - rays ) than the detected source spectrum . we may also decompose the point - like and diffuse components in the pn data spectrally . we extract a spectrum of the diffuse component in the @xmath90 annulus . from the same region , we also obtain a background spectrum from the re - projected blank - sky data . the use of this background spectrum minimizes the effect of instrumental background variation across the detector . however , the sky background typically varies from one field to another . to account for this variation , we adjust the background spectrum by adding the spectral difference between the and blank - sky data in an annulus between @xmath91 off x-1 . in all of these spectral extractions , the source regions are removed from both the and the blank - sky data . [ fig : spec_d ] shows the background - subtracted net spectrum of the diffuse x - ray component of . the apparent emission line features at @xmath92 and @xmath93 , corresponding to the ne x and mg xi k@xmath13 transitions , indicates that part of the component has a thermal origin . therefore , we fit this spectrum with the combination of an optically thin thermal plasma ( xspec _ mekal _ model ) and a power law to characterize the residual point - like source contribution . the fit is satisfactory ( @xmath94 ; fig . [ fig : spec_d ] ) and gives reasonable model parameters : @xmath95 , metal abundance @xmath96 , power law photon index @xmath97 , and @xmath98 ( assuming the solar metal abundance for the absorbing gas ) . the index is marginally greater than that inferred from the fit to the accumulated source spectrum ( 3.1 ) , which is probably due , in part , to our demand for the same @xmath34 for both the power law and the plasma components . indeed , these two power laws ( one from the source spectrum and the other from the spectral decomposition here ) give comparable predictions of the relative contribution of point - like sources in the 0.5 - 2 kev and 2 - 4.5 kev bands . thus we conclude that the residual point - like source contribution , corrected for the absorption , is @xmath99 in the 0.5 - 2 kev band and the corresponding hot gas luminosity is a factor of @xmath4 higher . if an extrapolation of the best - fit thermal plasma model to energies outside the band is a good approximation , the total cooling rate of the plasma should then be about @xmath100 .

we present an x - ray study of our nearest starburst galaxy ic 10 , based on _ xmm - newton _ and observations . the brightest source in the ic 10 field , x-1 , has a mean 0.3 - 8.0 kev luminosity of and shows a large variation by a factor of up to on time scales of s during the _ xmm - newton _ observation . there is evidence that the hot gas is driving outflows from the starburst regions ; therefore , the bulk of the energy inputs may be released in a galactic wind .

we present an x - ray study of our nearest starburst galaxy ic 10 , based on _ xmm - newton _ and observations . a list of 73 _ xmm - newton _ and 28 detections of point - like x - ray sources in the field is provided ; a substantial fraction of them are likely stellar objects in the milky way due to the low galactic latitude location of ic 10 . the brightest source in the ic 10 field , x-1 , has a mean 0.3 - 8.0 kev luminosity of and shows a large variation by a factor of up to on time scales of s during the _ xmm - newton _ observation . the x - ray spectra of the source indicate the presence of a multi - color blackbody accretion disk with an inner disk temperature kev . these results are consistent with the interpretation of the source as a stellar mass black hole , probably accreting from a wolf - rayet star companion . we infer the mass of this black hole to be m if it is not spinning , or a factor of up to higher if there is significant spinning . we also detect an apparent diffuse soft x - ray emission component of ic 10 . an effective method is devised to remove the x - ray ccd - readout streaks of x-1 that strongly affect the study of the diffuse component in the _ xmm - newton _ and observations . we find that the diffuse x - ray morphology is oriented along the optical body of the galaxy and is chiefly associated with starburst regions . the diffuse component can be characterized by an optically thin thermal plasma with a mean temperature of k and a 0.5 - 2 kev luminosity of , representing only a small fraction of the expected mechanical energy inputs from massive stars in the galaxy . there is evidence that the hot gas is driving outflows from the starburst regions ; therefore , the bulk of the energy inputs may be released in a galactic wind .

astro-ph0507041

i

we have conducted a careful analysis of the _ xmm - newton _ and x - ray ccd observations of the nearby starburst galaxy . in particular , we have devised an effective method to remove the ccd - readout streaks of the bright source x-1 . the main results of our analysis are as follows : * a list of 73 _ xmm - newton _ and 28 detections of point - like sources in the field is presented , including preliminary multi - wavelength identifications based on existing databases . while a large portion of these sources are likely to be foreground and background objects , those associated with tend to show hard x - ray spectral characteristics consistent with high - mass x - ray binaries . * we confirm that x-1 likely represents a bh / w - r binary system . the mean x-1 luminosity of @xmath0 in the 0.3 - 8.0 kev band is about the same during the _ xmm - newton _ and observations . but the source shows large luminosity variation by a factor of up to @xmath1 on time scales of @xmath2 s. the spectrum of x-1 is well characterized by a comptonized multi - color blackbody accretion disk with an inner disk temperature @xmath3 kev , typical of those persistent x - ray binaries with stellar mass bhs ( i.e. , lmc x-1 , lmc x-3 , and cyg x-1 ) . for x-1 , we infer the mass of the putative bh as @xmath4 m@xmath5 if it is not spinning , or a factor of up to @xmath1 higher if the spinning is important . * the presence of the diffuse soft x - ray emission in is revealed . the emission is morphologically oriented along the optical main body and is greatly enhanced around most active star - forming regions of the galaxy . the extent of the emission resembles that of luminous h@xmath13 streamers , emanating from starburst regions . the diffuse soft x - ray emission most likely arises from chemically - enriched hot gas with a characteristic temperature of @xmath126 kev and a total 0.5 - 2 kev luminosity of @xmath7 . although its total cooling rate ( @xmath127 ) is still quite uncertain , this hot gas could be easily maintained by the mechanical energy input from the observed large w - r star population in the galaxy . but the x - ray radiation is unlikely to be the main cooling mechanism of the hot gas , which apparently powers various energetic ism features observed around the starburst regions and will eventually escape from the galaxy . we thank the referee franz bauer for valuable comments on the work , which is supported by nasa through the grant nag5 - 13582 and the massachusetts space grant . this publication makes use of data products from the two micron all sky survey , which is a joint project of the university of massachusetts and the infrared processing and analysis center / california institute of technology , funded by the national aeronautics and space administration and the national science foundation . arnaud , k. a. 1996 , in astronomical data analysis software and systems v(asp conf . series volume 101 ) , eds . jacoby g. and barnes j. , p17 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@xmath128 & & @xmath129 & b , s + 2 & j001845.81 + 592331.9 & 3.1 & @xmath130 & & @xmath131 & s , b + 3 & j001855.81 + 591240.1 & 1.5 & @xmath132 & & @xmath133 & s , b + 4 & j001857.44 + 590458.5 & 3.4 & @xmath134 & & & b + 5 & j001902.38 + 591623.3 & 2.2 & @xmath135 & & @xmath136 & b , s + 6 & j001909.72 + 591916.0 & 2.7 & @xmath137 & & & b , s + 7 & j001910.26 + 592455.9 & 3.7 & @xmath138 & & & b , s + 8 & j001917.94 + 591231.9 & 2.2 & @xmath139 & & @xmath140 & b , s + 9 & j001918.64 + 590820.7 & 0.3 & @xmath141 & @xmath142 & @xmath143 & b , s , h + 10 & j001922.60 + 591541.7 & 3.3 & @xmath144 & & & b + 11 & j001925.54 + 591417.5 & 2.1 & @xmath145 & & @xmath146 & s , b + 12 & j001926.58 + 591103.5 & 3.2 & @xmath147 & & & s , b + 13 & j001927.16 + 592423.6 & 3.1 & @xmath148 & & & b , h + 14 & j001929.33 + 590420.9 & 3.0 & @xmath149 & & @xmath150 & b , s + 15 & j001938.11 + 591652.6 & 2.9 & @xmath151 & & & b , s + 16 & j001944.06 + 591815.9 & 2.5 & @xmath152 & @xmath153 & & h , b + 17 & j001947.84 + 591711.5 & 2.0 & @xmath154 & @xmath155 & & b , h + 18 & j001949.48 + 590620.6 & 3.0 & @xmath156 & & & b , s + 19 & j001949.69 + 591334.3 & 2.5 & @xmath157 & & & b + 20 & j001950.60 + 590440.4 & 3.5 & @xmath158 & & & b , s + 21 & j001951.82 + 591328.5 & 2.2 & @xmath159 & & @xmath160 & s + 22 & j001952.36 + 590704.5 & 3.3 & @xmath161 & & & b , s + 23 & j001952.73 + 590854.1 & 2.7 & @xmath162 & @xmath163 & & b , h + 24 & j002008.34 + 592144.5 & 2.0 & @xmath164 & @xmath165 & & b , h , s + 25 & j002008.36 + 591953.2 & 2.5 & @xmath166 & & & b + 26 & j002008.84 + 591338.5 & 2.1 & @xmath167 & & @xmath168 & b , s + 27 & j002010.78 + 592547.2 & 2.0 & @xmath169 & @xmath170 & & b , h , s + 28 & j002012.48 + 591500.4 & 1.1 & @xmath171 & @xmath172 & @xmath173 & b , s , h + 29 & j002015.10 + 591854.0 & 1.4 & @xmath174 & & @xmath175 & b , s + 30 & j002015.84 + 592637.2 & 2.8 & @xmath176 & & & b , h + 31 & j002018.03 + 590732.0 & 1.7 & @xmath177 & @xmath178 & @xmath179 & b , h , s + 32 & j002018.31 + 591834.5 & 2.8 & @xmath180 & & & h + 33 & j002021.57 + 591900.1 & 2.0 & @xmath181 & & & b , h , s + 34 & j002023.16 + 590812.8 & 2.0 & @xmath182 & & @xmath183 & b , s , h + 35 & j002023.46 + 591445.5 & 1.3 & @xmath184 & & @xmath185 & s , b + 36 & j002024.47 + 591525.7 & 0.5 & @xmath186 & @xmath187 & @xmath188 & b , s , h + 37 & j002025.84 + 591844.6 & 1.6 & @xmath189 & & @xmath190 & b , s , h + 38 & j002027.03 + 590613.8 & 3.0 & @xmath191 & & & b , s + 39 & j002029.10 + 591651.1 & 0.1 & @xmath192 & @xmath193 & @xmath194 & b , s , h + 40 & j002033.97 + 591112.0 & 3.2 & @xmath195 & & & s + 41 & j002034.07 + 591031.9 & 2.0 & @xmath196 & @xmath197 & & b , h + 42 & j002034.12 + 591555.6 & 1.2 & @xmath198 & & @xmath199 & b , s + 43 & j002036.20 + 592402.6 & 2.9 & @xmath200 & & & b , s + 44 & j002042.27 + 591709.6 & 2.6 & @xmath201 & & & b , h + 45 & j002042.63 + 591850.3 & 2.9 & @xmath202 & & & b + 46 & j002047.38 + 591935.4 & 2.1 & @xmath203 & @xmath165 & & b , h , s + 47 & j002050.24 + 591528.3 & 2.9 & @xmath204 & & & s , b + 48 & j002050.26 + 591505.1 & 2.7 & @xmath205 & & & b + 49 & j002052.96 + 591647.4 & 2.4 & @xmath206 & & & b , h + 50 & j002053.78 + 592106.4 & 3.3 & @xmath207 & & & s + 51 & j002058.62 + 590833.8 & 3.0 & @xmath208 & & & b + 52 & j002100.75 + 591104.9 & 3.0 & @xmath209 & & & s , b + 53 & j002101.69 + 591519.5 & 2.1 & @xmath210 & & @xmath211 & s , b + 54 & j002102.62 + 592158.0 & 1.8 & @xmath212 & @xmath213 & @xmath214 & b , s , h + 55 & j002103.82 + 590957.4 & 2.2 & @xmath215 & @xmath216 & & h , b + 56 & j002104.70 + 591540.2 & 1.8 & @xmath217 & & @xmath218 & s , b + 57 & j002108.72 + 591134.4 & 2.6 & @xmath219 & & & b , s , h + 58 & j002114.93 + 590844.5 & 1.7 & @xmath220 & & @xmath221 & b , s + 59 & j002117.67 + 591839.9 & 3.4 & @xmath222 & & & b + 60 & j002121.44 + 590905.7 & 0.9 & @xmath223 & & @xmath224 & b , s + 61 & j002125.43 + 591904.2 & 1.8 & @xmath225 & & @xmath226 & b , s + 62 & j002131.27 + 591428.0 & 2.6 & @xmath227 & & & b , s + 63 & j002132.53 + 591313.6 & 3.1 & @xmath228 & & & b + 64 & j002134.56 + 591443.6 & 2.8 & @xmath229 & & & b , s + 65 & j002139.04 + 592243.4 & 1.9 & @xmath230 & & @xmath231 & s , b + 66 & j002142.96 + 591207.3 & 3.4 & @xmath232 & & & b + 67 & j002144.80 + 591730.8 & 3.4 & @xmath233 & & & b + 68 & j002144.98 + 590736.2 & 3.3 & @xmath234 & & & b + 69 & j002151.67 + 590820.1 & 3.5 & @xmath235 & & & b , h + 70 & j002155.38 + 591008.5 & 2.6 & @xmath236 & & & b , s + 71 & j002158.87 + 591326.7 & 1.3 & @xmath237 & & @xmath238 & b , s + 72 & j002203.62 + 591515.4 & 3.9 & @xmath239 & & & b + 73 & j002209.37 + 591357.6 & 1.7 & @xmath240 & & @xmath241 & b , s + lrrrrrrrr 1 & j001954.74 + 591721.5 & 1.7 & @xmath242 & & & s , b + 2 & j002004.91 + 591507.4 & 0.7 & @xmath243 & & & b , h + 3 & j002008.41 + 591540.0 & 0.4 & @xmath244 & & & b , h + 4 & j002009.23 + 591818.3 & 0.9 & @xmath245 & & & b , h + 5 & j002011.49 + 591627.0 & 0.6 & @xmath246 & & & b , h + 6 & j002012.54 + 591757.8 & 0.3 & @xmath247 & & & h , b + 7 & j002012.75 + 591500.8 & 0.1 & @xmath248 & @xmath249 & @xmath250 & b , s , h + 8 & j002013.75 + 591626.6 & 0.2 & @xmath251 & & @xmath252 & b , s , h + 9 & j002015.04 + 591853.5 & 0.2 & @xmath253 & & @xmath254 & b , s + 10 & j002016.75 + 591556.2 & 0.8 & @xmath255 & & & h + 11 & j002020.99 + 591758.6 & 0.1 & @xmath256 & @xmath257 & @xmath258 & h , b , s + 12 & j002021.59 + 591901.5 & 0.5 & @xmath259 & & & b , h + 13 & j002022.92 + 591538.4 & 0.7 & @xmath260 & & & b + 14 & j002023.59 + 591444.0 & 0.1 & @xmath261 & & @xmath262 & b , s + 15 & j002024.54 + 591524.9 & 0.1 & @xmath263 & @xmath264 & @xmath265 & b , h , s + 16 & j002026.11 + 591844.7 & 0.5 & @xmath266 & & & s , b + 17 & j002026.68 + 591454.7 & 0.3 & @xmath267 & & & s , b + 18 & j002029.17 + 591651.2 & 0.0 & @xmath268 & @xmath269 & @xmath270 & b , h , s + 19 & j002030.74 + 591743.8 & 0.7 & @xmath271 & & & b , h + 20 & j002034.67 + 591556.8 & 0.2 & @xmath272 & & @xmath273 & b , s , h + 21 & j002038.76 + 591740.7 & 0.3 & @xmath274 & & & b , h + 22 & j002040.14 + 591435.3 & 0.8 & @xmath275 & & & s + 23 & j002041.41 + 591712.4 & 0.9 & @xmath276 & & & h + 24 & j002046.45 + 591731.4 & 0.4 & @xmath277 & & & s , b + 25 & j002047.30 + 591320.2 & 0.7 & @xmath278 & & & b , s + 26 & j002050.06 + 591504.9 & 2.3 & @xmath279 & & & b + 27 & j002050.18 + 591408.7 & 0.8 & @xmath280 & & & b , h + 28 & j002052.81 + 591648.5 & 0.4 & @xmath281 & & & b , h , s + lccrrrrr xp-1 & j001834.91 + 591947.6 & 1.2 & 12.4 11.7 11.5 + xp-3 & j001855.89 + 591240.6 & 0.8 & 12.8 12.1 11.9 + xp-9 & j001918.74 + 590820.3 & 0.9 & 6.9 6.8 6.8 + xp-11 & j001925.62 + 591419.1 & 1.7 & 14.0 13.3 13.1 + xp-12 & j001926.70 + 591105.4 & 2.1 & 14.2 13.7 13.6 + xp-16 & j001944.20 + 591812.5 & 3.6 & 15.3 14.9 14.7 + xp-19 & j001949.37 + 591333.7 & 2.6 & 15.5 14.7 14.6 + xp-21 & j001951.75 + 591327.1 & 1.5 & 11.6 11.2 11.1 + xp-34 & j002023.22 + 590814.0 & 1.2 & 16.2 15.7 14.5 + xp-35/xa-14 & j002023.51 + 591444.7 & 1.0 & 8.8 8.5 8.5 + xp-37/xa-16 & j002025.98 + 591845.3 & 1.3 & 15.4 14.4 14.7 + xp- 38 & j002026.57 + 590615.6 & 4.0 & 15.1 14.6 14.3 + xp-40 & j002034.39 + 591114.1 & 3.8 & 15.1 14.6 14.3 + xp-41 & j002033.80 + 591033.5 & 2.6 & 13.0 12.2 12.0 + xp-42/xa-20 & j002034.58 + 591557.3 & 3.9 & 13.9 13.3 13.1 + xp-43 & j002036.24 + 592405.6 & 3.0 & 16.4 15.8 15.4 + xp-45 & j002042.67 + 591851.4 & 1.1 & 15.1 14.5 14.4 + xp-47 & j002050.13 + 591525.9 & 2.6 & 15.3 14.6 14.3 + xp-50 & j002053.89 + 592108.2 & 2.0 & 12.2 11.6 11.4 + xp-52 & j002101.03 + 591104.5 & 2.2 & 14.9 14.1 14.0 + xp-53 & j002101.55 + 591518.1 & 1.8 & 10.6 9.9 9.7 + xp-56 & j002104.59 + 591539.9 & 0.9 & 11.2 10.9 10.7 + xp-58 & j002114.77 + 590845.5 & 1.6 & 10.9 10.6 10.5 + xp-60 & j002121.38 + 590905.3 & 0.6 & 11.0 10.6 10.5 + xp-61 & j002125.69 + 591904.9 & 2.1 & 14.0 13.5 13.2 + xp-65 & j002139.00 + 592243.3 & 0.3 & 14.4 13.8 13.5 + xp-71 & j002158.82 + 591327.2 & 0.7 & 11.8 11.4 11.2 + xp-73 & j002209.58 + 591401.1 & 3.8 & 12.4 12.0 11.9 + xa-11 & j002020.90 + 591759.0 & 0.8 & 16.4 15.4 15.5 + xa-13 & j002022.80 + 591539.0 & 1.1 & 13.5 13.2 13.1 + xa-17 & j002026.61 + 591455.9 & 1.3 & 13.7 13.0 12.7 + xa-22 & j002040.10 + 591435.5 & 0.3 & 10.8 10.4 10.2 + xa-24 & j002046.44 + 591731.8 & 0.4 & 15.4 14.8 14.4 + xa-25 & j002047.26 + 591321.2 & 1.1 & 14.8 14.1 13.9 +

a list of 73 _ xmm - newton _ and 28 detections of point - like x - ray sources in the field is provided ; a substantial fraction of them are likely stellar objects in the milky way due to the low galactic latitude location of ic 10 . the x - ray spectra of the source indicate the presence of a multi - color blackbody accretion disk with an inner disk temperature kev . we infer the mass of this black hole to be m if it is not spinning , or a factor of up to higher if there is significant spinning . an effective method is devised to remove the x - ray ccd - readout streaks of x-1 that strongly affect the study of the diffuse component in the _ xmm - newton _ and observations . we find that the diffuse x - ray morphology is oriented along the optical body of the galaxy and is chiefly associated with starburst regions . the diffuse component can be characterized by an optically thin thermal plasma with a mean temperature of k and a 0.5 - 2 kev luminosity of , representing only a small fraction of the expected mechanical energy inputs from massive stars in the galaxy .

we present an x - ray study of our nearest starburst galaxy ic 10 , based on _ xmm - newton _ and observations . a list of 73 _ xmm - newton _ and 28 detections of point - like x - ray sources in the field is provided ; a substantial fraction of them are likely stellar objects in the milky way due to the low galactic latitude location of ic 10 . the brightest source in the ic 10 field , x-1 , has a mean 0.3 - 8.0 kev luminosity of and shows a large variation by a factor of up to on time scales of s during the _ xmm - newton _ observation . the x - ray spectra of the source indicate the presence of a multi - color blackbody accretion disk with an inner disk temperature kev . these results are consistent with the interpretation of the source as a stellar mass black hole , probably accreting from a wolf - rayet star companion . we infer the mass of this black hole to be m if it is not spinning , or a factor of up to higher if there is significant spinning . we also detect an apparent diffuse soft x - ray emission component of ic 10 . an effective method is devised to remove the x - ray ccd - readout streaks of x-1 that strongly affect the study of the diffuse component in the _ xmm - newton _ and observations . we find that the diffuse x - ray morphology is oriented along the optical body of the galaxy and is chiefly associated with starburst regions . the diffuse component can be characterized by an optically thin thermal plasma with a mean temperature of k and a 0.5 - 2 kev luminosity of , representing only a small fraction of the expected mechanical energy inputs from massive stars in the galaxy . there is evidence that the hot gas is driving outflows from the starburst regions ; therefore , the bulk of the energy inputs may be released in a galactic wind .

1611.04543

i

the coupling between carriers and phonons is known or believed to be important for many materials , including cuprates,@xcite manganites , @xcite , nickelates @xcite and bismuth perovskites.@xcite these materials display a variety of interesting phenomena , including , but not limited to , high - temperature superconductivity ( cuprates , babio@xmath2 ) , layered ferromagnetism ( manganites ) and a spin / charge density wave ( nickelates ) . the carrier - phonon coupling leads to the formation of a polaron , a coherent quasi - particle ( qp ) consisting of the charge carrier and the cloud of phonons surrounding it and moving coherently with it . polarons have been studied extensively especially in the holstein model , @xcite the simplest model where local phonons modify the on - site energy of the carrier , but also to generalizations with short - range and long - range couplings of similar origin , such as the breathing - mode ( bm ) model @xcite , the double - well potential model@xcite and the frhlich model @xcite . the other possibility is that the coupling to phonons modulates the carrier s hopping integrals , a scenario described by the ssh model , @xcite which has seen an increased amount of interest in recent years.@xcite this is because the ssh model exhibits a sharp transition in the properties of its polaron , one signature being the change of the polaron ground state ( gs ) momentum from @xmath1 ( at weak coupling ) to a finite value that smoothly evolves toward @xmath3 ( at strong coupling ) . such transitions were shown to be impossible for models where the phonons modulate the on - site energy @xcite.a study of a model which includes both types of carrier - phonon coupling was carried out by herrera _ et . al _ @xcite and found that in addition to the transition observed in the ssh model , a second transition of the gs momentum also takes place . whether other such transitions can occur and what are their characteristics , is currently an open question . efforts to understand polaron physics have , so far , focused almost exclusively on single - band models . it is therefore a natural question to ask whether the polaron properties of multi - band models are similar , or whether they are qualitatively different from those of single band models . in this article , we answer this question based on a study of the single polaron properties of the two - band model depicted in fig . [ fig : model ] , with two different atoms per unit cell , one of which is light and thus supports lattice vibrations ( optical phonons ) . the coupling to this phonon mode modulates the hopping integrals , in direct analogy with the one - band ssh model.(for the vanishing carrier concentration of interest to us , the ssh - model is a one - band model because the peierls dimerization only occurs at half - filling @xcite ) . due to a phonon on site @xmath4 is also shown . ] given this similarity , one may expect our two - band model to behave like the ssh model , and indeed we find a sharp transition at strong carrier - hole coupling , where the polaron gs momentum changes its value . however , unlike in the one - band ssh model where the gs momentum changes continuously with coupling , in our model the gs momentum jumps discontinuously from @xmath5 to @xmath1 . furthermore , this transition leads to an extreme flattening of the polaron band , unlike in the ssh model . we conclude that this transition is qualitatively different from that of the one - band ssh model . we argue that the mechanism for the transition is a competition between the bare carrier hopping which favors a gs momentum @xmath5 , and the phonon - modulated hopping which favors @xmath1 . while some of this physics is similar to that explaining the transition in the ssh model , we find strong indications that the two - band nature of our model plays a vital role . this makes it unlikely that such a discontinuous transition can occur in a one - band model . the physics described in this article is therefore , to our knowledge , fundamentally new and our findings hint at the possibility that there is still more , new polaron physics to be discovered in other multi - band models . the physical inspiration for our model is the perovskite babio@xmath2 , which is known to have strong electron - phonon coupling and to exhibit superconductivity up to surprisingly high temperatures upon hole doping ( @xmath6 in the case of ba@xmath7k@xmath8bio@xmath2 @xcite and @xmath9 for bapb@xmath7bi@xmath10o@xmath2 ) @xcite , widely believed to be due to a phononic glue @xcite . the relevant valence orbitals are the bi 6@xmath11 orbitals and the o 2@xmath12 orbitals . previous work on polarons and bipolarons in this material was carried out by allen _ _ @xcite and is based on the rice - sneddon model @xcite which assumes that the bi atoms undergo charge disproportionation , bi@xmath13bi@xmath14bi@xmath15bi@xmath16 . this scenario has received wide - spread attention @xcite , and as a consequence many model hamiltonians only take into account the bi 6@xmath11 orbitals . polaronic signatures in agreement with this work have also been found experimentally @xcite . a different scenario is provided by a recent study of foyevtsova _ et . _ @xcite and the experimental as well as theoretical work of menushenkov _ et al _ @xcite . _ argue that the bio@xmath17 octahedra undergo a breathing distortion due to strong hybridization between the bi 6@xmath11 and o 2@xmath12 orbitals , with the holes being located primarily on the o. this picture is similar to that proposed recently for the nickelates @xcite and the inspiration for our `` toy model '' . in this picture both the bi 6@xmath11 and o 2@xmath12 orbitals need to be taken into account . since o atoms are much lighter than bi atoms , only optical phonons on the o atoms are considered and are allowed to modulate the hopping integrals . when compared to other perovskites such as the cuprates , manganites and nickelates , babio@xmath2 is appealing because of its comparatively simple electronic structure and absence of magnetic properties . to simplify things even more , instead of considering a model describing such a material at or near half filling , as it is in reality , we investigate the single polaron physics in its almost fully compensated case , _ i.e. _ like in labio@xmath2 with one extra hole . generalizing to one carrier ( polaron ) per unit cell will be left for future work . moreover , as indicated above , we restrict ourselves to study a 1d bio - like chain , instead of treating the full 3d system . there are two practical reasons for these simplifications : ( i ) they make comparison to the ssh model , where polaron results are currently available only for the 1d model , possible ; ( ii ) they allow us to use exact diagonalization ( ed ) to find essentially exact results very efficiently,@xcite which in turn also allows us to probe a wide range of coupling strengths and phonon frequencies to understand the relevant physics . beside using ed to understand the polaron properties of this model , we also develop and validate here two simple versions of the variational momentum average ( ma ) approximation,@xcite which capture the relevant polaronic physics qualitatively and even quantitatively . ma approaches are very useful because their accuracy improves in higher dimensions while maintaining similar computational efficiency . this is in contrast to ed and most other numerical methods that become very costly due to the significant increase of the hilbert space in higher dimensions . this work can therefore be seen as a first step towards a study of the 3d systems . note that apart from their usefulness in treating more complex problems , developing such approximations also leads to a better understanding of the nature of the polaron s cloud . to summarize , the research presented in this article serves two main purposes : ( i ) to reveal surprising , new polaron physics whose nature appears to be tied to the two - band nature of our model , and ( ii ) to serve as a test - ground for approximations which will be useful in solving the 3d many - band problem , and thus help to improve our understanding of the fascinating compound babio@xmath2 , if the scenario of foyevtsova _ et _ turns out to be valid , or of other many - band materials with hopping - modulated carrier - phonon coupling . the remainder of this article is organized as follows : in sec . [ sec : model ] we introduce the model and in sec . [ sec : methods ] we introduce the ed algorithm , ma and a perturbation theory . the results are presented in sec . [ sec : results ] and sec . [ sec : conclusions ] contains our conclusions .

, we find a novel type of sharp transition , where the polaron ground state momentum jumps discontinuously from to . the nature and origin of this transition is investigated and compared to that of the su - schrieffer - heeger ( ssh ) model , where a sharp but smooth transition was previously reported . we argue that such discontinuous transitions are a consequence of the multi - band nature of the model , and are unlikely to be observed in one - band models . we also show that ma describes qualitatively and even quantitatively accurately this polaron and its transition .

we present exact diagonalization and momentum average approximation ( ma ) results for the single polaron properties of a one - dimensional two - band model with phonon - modulated hopping . at strong electron - phonon coupling , we find a novel type of sharp transition , where the polaron ground state momentum jumps discontinuously from to . the nature and origin of this transition is investigated and compared to that of the su - schrieffer - heeger ( ssh ) model , where a sharp but smooth transition was previously reported . we argue that such discontinuous transitions are a consequence of the multi - band nature of the model , and are unlikely to be observed in one - band models . we also show that ma describes qualitatively and even quantitatively accurately this polaron and its transition . given its computationally efficient generalization to higher dimensions , ma thus promises to allow for accurate studies of electron - phonon coupling in multi - band models in higher dimensions .

1505.03158

i

over the past two decades , observations of exoplanets have uncovered a stunning diversity of systems . major improvements in the capabilities of space- and ground - based telescopes in recent years have led to the discovery and characterization of hundreds of new exoplanets , covering a broad range of orbital properties , interior and atmospheric compositions , and host star types @xcite . meanwhile , these same technological advances have enabled the detailed study of the atmospheric properties of the brightest and largest planets through high - precision photometry and spectroscopy . most of these targets belong to the class of gas giant planets known as hot jupiters . the high levels of incident flux , slow rotation , and potentially large temperature gradients between hemispheres characteristic of these planets allow us to test atmospheric models in a new regime unlike any found in the solar system . in addition , hot jupiters are some of the most favorable targets for measuring elemental abundances , since most material is not in a condensed form at these high temperatures ( e.g. , * ? ? ? atmospheric circulation models of hot jupiters predict broad super - rotating equatorial jets that circulate energy between the day and night sides , with the precise effect of these winds on the day - to - night temperature contrast being strongly dependent on the particular orbital and atmospheric properties of the planet ( see * ? ? ? * and references therein ) . as a result of their short orbital periods , hot jupiters have high atmospheric temperatures and emit relatively strongly at infrared wavelengths , allowing for direct measurement of their atmospheric brightness as a function of orbital phase . these phase curves can then be converted into a longitudinal temperature profile @xcite . by comparing the measured phase curves to theoretical phase curves generated by atmospheric models , we can constrain fundamental properties of the atmosphere , such as the efficiency of heat transport from the day side to the night side , radiative time scales , wind speeds , and compositional gradients between the day and night sides . to date , well - characterized phase curve observations have been published for eleven planets : @xmath10 and b @xcite , hd 189733b @xcite , hd 149026b @xcite , hd 80606b @xcite , hat - p-7b @xcite , kepler-7b @xcite , corot-1b @xcite , wasp-12b @xcite , wasp-18b @xcite , hat - p-2b @xcite , and hd 209458b @xcite . the majority of these observations were carried out using the _ spitzer space telescope _ while the rest were obtained at optical wavelengths by the _ corot _ and _ kepler _ missions . recently , the first spectroscopic phase curve was obtained for the hot jupiter wasp-43b using the _ hubble space telescope _ between 1.2 and 1.6 @xmath1 m @xcite . in this paper , we present full - orbit phase curves of the hot jupiter wasp-14b in the 3.6 and 4.5 @xmath1 m bands obtained with the _ spitzer space telescope_. photometric and radial - velocity observations of wasp-14b indicate a mass of @xmath11 and a radius of @xmath12 , corresponding to a density of @xmath13 @xcite . the planet lies on an eccentric orbit ( @xmath14 ; * ? ? ? * ) around a young host star ( age @xmath15 gyr , spectral type f5 , @xmath16 , @xmath17 , @xmath18 k , and @xmath19 ; * ? ? ? * ; * ? ? ? * ) , with a period of 2.24 days and an orbital semi - major axis of @xmath20 au . the equilibrium temperature of wasp-14b is relatively high ( @xmath21 k , assuming zero albedo and reemission from the entire surface ; * ? ? ? * ) , suggesting that the thermal evolution of wasp-14b may be significantly affected by ohmic dissipation in a partially - ionized atmosphere ( e.g. , @xcite ; but for debate see @xcite ) . @xcite analyzed secondary eclipse observations in the 3.6 , 4.5 , and 8.0@xmath1 m _ spitzer _ bands and found no evidence for a thermal inversion in the dayside atmosphere , while concluding that the data are consistent with relatively poor energy redistribution from dayside to nightside . @xcite find that , based on the dayside fluxes , the most highly - irradiated planets have systematically less efficient day / night heat circulation . @xcite reached a similar conclusion from a comparison of the fractional day - night flux differences of planets for which phase curves have been obtained . this overall trend has been explained by hydrodynamical models @xcite . phase curve observations at more than one wavelength provide complementary information about the properties of the planet s atmosphere , as different wavelengths probe different pressure levels within the atmosphere . multiband measurements of the planet s brightness can also be transformed into low - resolution dayside and nightside emission spectra , which can reveal differences in atmospheric composition . only five systems have phase curve observations at more than one wavelength : hd 189733 @xcite , wasp-12 @xcite , wasp-18 @xcite , hat - p-2 @xcite , and wasp-43 @xcite . while single - wavelength phase curves can be reasonably well - matched by standard atmospheric circulation models , none of the multi - wavelength phase curves are satisfactorily reproduced by these same models . this suggests that our understanding of the physical and chemical processes that drive atmospheric circulation is still incomplete . the paper is organized as follows : the observations and data reduction methodology are described in section [ sec : obs ] . in section [ sec : analysis ] , we discuss the phase curve model used in our analysis and present the best - fit parameters . we then use our results to obtain updated orbital parameters and discuss the implications of our phase curve fits for the planet s atmospheric dynamics in section [ sec : dis ] .

we present full - orbit phase curve observations of the eccentric ( ) transiting hot jupiter wasp-14b obtained in the 3.6 and 4.5 m bands using the _ spitzer space telescope_. we use two different methods for removing the intrapixel sensitivity effect and compare their efficacy in decoupling the instrumental noise .

we present full - orbit phase curve observations of the eccentric ( ) transiting hot jupiter wasp-14b obtained in the 3.6 and 4.5 m bands using the _ spitzer space telescope_. we use two different methods for removing the intrapixel sensitivity effect and compare their efficacy in decoupling the instrumental noise . our measured secondary eclipse depths of and at 3.6 and 4.5 m , respectively , are both consistent with a blackbody temperature of k. we place a upper limit on the nightside flux at 3.6 m and find it to be of the dayside flux , corresponding to a brightness temperature of 1079 k. at 4.5 m , the minimum planet flux is of the maximum flux , corresponding to a brightness temperature of k. we compare our measured phase curves to the predictions of one - dimensional radiative transfer and three - dimensional general circulation models . we find that wasp-14b s measured dayside emission is consistent with a model atmosphere with equilibrium chemistry and a moderate temperature inversion . these same models tend to over - predict the nightside emission at 3.6 m , while under - predicting the nightside emission at 4.5 m . we propose that this discrepancy might be explained by an enhanced global c / o ratio . in addition , we find that the phase curves of wasp-14b ( ) are consistent with a much lower albedo than those of other jovian mass planets with thermal phase curve measurements , suggesting that it may be emitting detectable heat from the deep atmosphere or interior processes .

1505.03158

c

we combine the two transit times calculated from our phase curve observations with all other published values @xcite to arrive at an updated ephemeris for the wasp-14 system . here , we define the zeroth epoch as that of the transit nearest in time to the error - weighted mean of all measured transit times . the transit observations span more than 5.3 years , and by fitting a line through the transit times , we derive new , more precise estimates of the orbital period @xmath146 and mid - transit time @xmath147 : @xmath148 figure [ transitoc ] shows the observed minus calculated transit times derived from these updated ephemeris values . we use the secondary eclipse times to obtain a second , independent estimate of the orbital period . carrying out a linear fit through the four secondary eclipse times calculated from our phase curve data and the two secondary eclipse times published in @xcite , we arrive at a best - fit value of @xmath149 days . this period is consistent with the best - fit transit period at the @xmath150 level . in figure [ eclipseoc ] , we plot the orbital phase of secondary eclipse for all published secondary eclipse times using the updated transit ephemeris values in eq . . the error - weighted mean orbital phase of secondary eclipse is @xmath151 . lrr[t ! ] @xmath152 & 2.24376524 @xmath153 & days + @xmath154 & 2456034.21261 @xmath155 & @xmath156 + @xmath157 & 0.0830 @xmath158 & + @xmath159 & 252.67 @xmath160 & degrees + @xmath161 & 986.4 @xmath162 & m s@xmath163 + @xmath164 & 155.8 @xmath165 & m s@xmath163 + @xmath166 & @xmath2270.0 @xmath167 & m s@xmath163 + @xmath168 & @xmath2273.7 @xmath169 & m s@xmath163 + @xmath170 & 187.4 @xmath171 & m s@xmath163 + @xmath172 & 0.0025 @xmath173 & m s@xmath163day@xmath163 + @xmath174 & @xmath220.02474 @xmath175 & + @xmath176 & @xmath220.0792 @xmath177 & + [ tab : rv ] . the black diamonds are the two transit times measured from our phase curve data.,width=340 ] . the black diamonds are the four secondary eclipse times measured from our phase curve data . the solid and dashed lines indicate the error - weighted mean phase value and corresponding @xmath142 confidence bounds , respectively . the horizontal axis has been condensed for clarity.,width=340 ] by combining the updated transit ephemeris and secondary eclipse times derived from the global phase - curve fits with the radial velocity measurements analyzed in @xcite , we can obtain new estimates of the orbital eccentricity and pericenter longitude : @xmath178 and @xmath179 degrees . these values are consistent with those reported in @xcite . we use the updated values of orbital eccentricity and pericenter longitude in our final phase curve fits ( table [ tab : values ] ) . results from our radial velocity fits are shown in table [ tab : rv ] and figure [ rv ] . these fits provide new estimates of the orbital period ( @xmath152 ) and center of transit time ( @xmath154 ) , as well as the semi - amplitude of the planet s radial velocity ( @xmath161 ) , the radial velocity zero point offsets for data collected by each of the different spectrographs from which radial velocity measurements of the system were obtained ( @xmath180 ) , and the slope ( @xmath172 ) of the best - fit radial velocity acceleration . the radial velocity slope is consistent with zero , indicating no evidence for additional planets in the wasp-14 system . from the rv fits we also arrive at updated values of the orbital semi - major axis and planet mass : @xmath181 au and @xmath182 . using the error - weighted best - fit values of @xmath47 and @xmath49 from both bandpasses , we obtain a new estimate of the planet s radius : @xmath183 . a full list of updated planetary parameters is give in table [ tab : newvalues ] . l m0.001 cm c & & + @xmath49 & & @xmath184 + @xmath47 & & @xmath185 + @xmath33 @xmath186 & & @xmath187 + @xmath133 & & @xmath188 + @xmath134 @xmath186 & & @xmath189 + @xmath190 @xmath191 & & @xmath192 + @xmath193 @xmath194 & & @xmath195 + @xmath196 ( g @xmath197 ) & & @xmath198 + @xmath199 ( m s@xmath200 ) & & @xmath201 + @xmath202 ( au ) & & @xmath203 + in this section , we combine the results of our global fits with model - generated spectra and light curves to provide constraints on the atmospheric properties of the planet . to compute the relative planet - star flux ratio phase curve @xmath204 , we subtract the secondary eclipse depth from the best - fit phase curve and divide by the remaining flux measured at the center of secondary eclipse , which represents the brightness of the star alone . for the secondary eclipse depths in each bandpass , we take the error - weighted average of the depths listed in table [ tab : values ] . the resulting phase curves are shown in figure [ lightcurve ] along with the corresponding @xmath205 brightness bounds . lll measured & @xmath206 & @xmath207 + eq . model & @xmath208 & @xmath209 + no tio model & @xmath210 & @xmath211 + + measured & @xmath212 & @xmath213 + eq . chem . model & @xmath214 & @xmath215 + no tio model & @xmath216 & @xmath217 + + measured & @xmath218 & @xmath219 + eq . chem . model & @xmath220 & @xmath221 + no tio model & @xmath222 & @xmath223 + + measured & @xmath124 & @xmath125 + eq . model & @xmath224 & @xmath225 + no tio model & @xmath226 & @xmath227 + + measured & @xmath126 & @xmath127 + eq . model & @xmath228 & @xmath229 + no tio model & @xmath230 & @xmath230 + [ tab : comparison ] some of the main quantitative characteristics of the phase curves are summarized in table [ tab : comparison ] . notably , the fluxes at both _ spitzer _ wavebands peak significantly before secondary eclipse , implying that the hottest regions are shifted eastward from the substellar point . this behavior appears to be common on hot jupiters and , in addition to wasp-14b , has also been clearly observed on hd 189733b @xcite , hd 209458b @xcite , hat - p-2b @xcite , wasp-43b @xcite , wasp-12b @xcite , and ups and b @xcite . this behavior was predicted before the _ spitzer _ era @xcite and has now been reproduced in a wide variety of general circulation models ( gcms , e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) . in these models , the eastward hotspot displacement results from eastward advection due to a fast , eastward - flowing jet stream centered at the equator . given such a jet , a significant hot spot offset occurs under conditions when the radiative timescale at the photosphere is comparable to timescales for air to advect horizontally over a planetary radius . the eastward offsets in our observations thus provide evidence that wasp-14b exhibits an eastward equatorial jet stream . it is interesting to compare our observed day - night flux differences with those of other planets observed to date . as mentioned previously , @xcite and @xcite inferred that , in general , planets that receive higher stellar fluxes exhibit larger fractional day - night temperature differences and less efficient day - night heat redistribution than planets that receive lower stellar fluxes . averaging the phase curve amplitudes at 3.6 and 4.5 @xmath1 m ( listed in table [ tab : comparison ] ) , we find that wasp-14b is roughly consistent with this trend , with a day - night flux difference that is smaller than those of highly - irradiated planets like wasp-12b and wasp-18b , but larger than those of more weakly - irradiated planets like hd 189733b and hd 209458b . we consider four types of atmosphere models . first , we use an interpolated phoenix spectrum for the host star wasp-14 @xcite to calculate the brightness temperatures of wasp-14b in each band from the retrieved secondary eclipse depths . the best - fit brightness temperatures are @xmath231 k at 3.6 @xmath1 m and @xmath232 k at 4.5 @xmath1 m . we find that the 3.6 and 4.5 @xmath1 m eclipse depths are consistent with a single blackbody temperature and derive an effective temperature of @xmath233 k from a simultaneous fit to both bandpasses . the predicted equilibrium temperature for wasp-14b assuming zero albedo is 2220 k if incident energy is re - radiated from the dayside only and 1870 k if the planet re - radiates the absorbed flux uniformly over its entire surface . we can also compare the computed brightness temperatures to the effective temperature of the dayside in the no - albedo , no - circulation limit assuming each region is a blackbody locally in equilibrium with the incident stellar flux : 2390 k @xcite . the high brightness temperatures from the blackbody fits therefore suggest that wasp-14b has a very hot dayside atmosphere and inefficient day - night recirculation . next , we compare our phase curves and emission spectra to theoretical models generated from the three - dimensional substellar and planetary atmospheric radiation and circulation ( sparc ) model to investigate the global circulation of wasp-14b . the sparc model was specifically developed with the study of extrasolar planetary atmospheres in mind @xcite . the sparc model couples the mitgcm @xcite with the non - gray radiative transfer model of @xcite in order to self - consistently calculate the amount of heating / cooling at each grid point . in this way , the sparc model does not require advective tuning parameters often employed in one - dimensional radiative transfer models or prescribed pressure - temperature profiles utilized in newtonian cooling schemes employed in other circulation models . our use of an atmospheric model that fully couples radiative and dynamical processes is especially important for planets on eccentric orbits , such as wasp-14b , which experience time variable heating @xcite . m ( filled black circles ) with sparc model emission spectra at the time of secondary eclipse and the time of transit , corresponding to the dayside and nightside of the planet . for the measured nightside 3.6 @xmath1 m emission , the @xmath5 upper limit is shown . solid lines indicate the predicted spectra for the equilibrium chemistry ( blue ) and no tio models ( red ) . band - averaged fluxes are overplotted as filled points of the same color . the black lines at the bottom represent the photometric band transmission profiles , in arbitrary units . the measured dayside 3.6 and 4.5 @xmath1 m planetary fluxes are bounded by the two models , suggesting a possible sub - solar abundance of tio / vo ; neither model reproduces the low measured 8.0 @xmath1 m dayside emission , which is derived from a single secondary eclipse measurement previously published in @xcite . meanwhile , the measured nightside planetary fluxes in both the 3.6 and 4.5 @xmath1 m bands are highly discrepant from the model - predicted values , which may point toward an enhanced atmospheric c / o ratio.,width=340 ] .,width=340 ] the sparc models of wasp-14b presented here utilize the cubed - sphere grid @xcite with a horizontal grid resolution of roughly @xmath234 in latitude and longitude ( a so - called low - resolution c16 grid ) . in the vertical direction , the models span pressures ranging from 200 bar to 0.2 mbar with 39 layers evenly spaced in @xmath235 and a top layer that extends to zero pressure . here we consider atmospheric compositions in thermochemical equilibrium both with and without the incorporation of the strong optical absorbers tio and vo ( hereafter , `` equilibrium chemistry '' and `` no tio '' , respectively ) . the presence of tio / vo in our models allows for the development of a dayside inversion layer @xcite . all models adopt solar elemental ratios of heavy elements . we assume that wasp-14b is in a pseudo - synchronous rotation state ( p@xmath236 days ; * ? ? ? * ) . as in the case of gj 436b , wasp-14b s relatively low eccentricity means that assuming pseudo - synchronous rotation instead of synchronous rotation is not likely to strongly affect the global circulation patterns that develop @xcite . figure [ lightcurve ] compares the best - fit phase curve derived from the _ spitzer _ data in each bandpass with the band - averaged light curves generated from the sparc model using the methods of @xcite . model dayside and nightside spectra at the center of secondary eclipse and center of transit times are shown in figure [ jonathan ] along with the corresponding measured flux ratios . the corresponding dayside and nightside temperature - pressure profiles generated by the models are shown in figure [ jonathantp ] . for the dayside planetary emission , we combine the 3.6 and 4.5 @xmath1 m flux ratios reported in the present work and previously in @xcite to arrive at the error - weighted average values : @xmath237 at 3.6 @xmath1 m and @xmath238 at 4.5 @xmath1 m . we also include the measured 8.0 @xmath1 m flux ratio ( @xmath239 ) from @xcite . table [ tab : comparison ] compares the model - predicted maximum and minimum flux ratios and time offsets with the values derived from the data . in both the 3.6 and 4.5 @xmath1 m bandpasses , the measured dayside planetary emission lies between the equilibrium chemistry and no tio models . a possible explanation is that the dayside atmosphere of wasp-14b may contain a sub - solar abundance of tio / vo ( possibly due to cold trapping ) , which would result in a weaker temperature inversion than the one predicted by the solar abundance equilibrium chemistry model ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? meanwhile , the measured 8.0 @xmath1 m dayside brightness is not reproduced by either of the models . we report offsets in the time of maximum and minimum flux relative to the center of transit and center of secondary eclipse times , respectively , as derived from our phase curve analysis and the models ( table [ tab : comparison ] ) . negative time offsets of the maximum or minimum flux indicate an eastward shift in the location of the hot or cold region in the planet s atmosphere . the no tio model greatly overestimates the magnitude of the minimum flux offsets while giving good agreement with the maximum flux offsets at both wavelengths . the equilibrium chemistry model yields a less severe overestimation of the minimum flux offset , while predicting a maximum flux offset that is opposite the one measured from the data . we find that overall the equilibrium chemistry model yields the closer match . the no tio model predicts a significant asymmetry in the phase curve around the time of minimum flux , which is not seen in the _ spitzer _ data . the most notable discrepancy between the best - fit phase curves and the sparc model results is in the nightside planetary flux . both the equilibrium chemistry and the no tio model overestimate the planet s nightside brightness at 3.6 @xmath1 m , while underestimating the brightness at 4.5 @xmath1 m . the planet s very low 3.6 @xmath1 m nightside emission indicates a higher atmospheric opacity at that wavelength than is predicted by the models . meanwhile , the higher - than - predicted 4.5 @xmath1 m nightside emission points toward a slight reduction in the atmospheric opacity at that wavelength relative to the models . one possible explanation for both of these trends is an increased c / o ratio . @xcite demonstrate that increasing the c / o ratio above equilibrium values leads to an excess of ch@xmath240 and a depletion of co. this enhances the opacity in the 3.6 @xmath1 m bandpass where ch@xmath240 has strong vibrational bands , while reducing the opacity in the 4.5 @xmath1 m bandpass where co has strong vibrational bands . an enhanced c / o ratio can also be invoked to explain the higher amplitude of the 3.6 @xmath1 m phase curve as compared with the 4.5 @xmath1 m phase curve . in this scenario the 3.6 @xmath1 m bandpass would probe lower pressure regions that have strong day / night contrasts due to a combination of short radiative timescales and the possible presence of a dayside temperature inversion . a relative depletion of co would shift the 4.5 @xmath1 m photosphere to higher pressures , where longer radiative timescales facilitate more efficient day - night heat transport , resulting in a reduced phase curve amplitude . we note , however , that recent spectroscopic surveys of m dwarfs suggest that the occurrence of high c / o ratios in stellar atmospheres appears to be low ( see * ? ? ? * and references therein ) . at the same time , models of disk chemistry predict that the c / o ratio of the solids and gas in the disk may vary as a function of disk radius ( e.g. , * ? ? ? * ; * ? ? ? * ) . in particular , different snowlines of oxygen- and carbon - rich ices are expected to result in systematic variations in the c / o ratio of gaseous material across the protoplanetary disk . gas giants that derive most of their atmosphere from the gas disk outside of the water snowline but inside of the carbon dioxide snowline may therefore end up with high atmospheric c / o ratios . we also note that @xcite showed that planets with high c / o ratios should naturally have less tio and correspondingly weaker temperature inversion , consistent with our previous discussion of wasp-14b s dayside emission . in addition , @xcite show that atmospheric models with high c / o ratios often predict reduced emission at longer wavelengths ( @xmath241 @xmath1 m ) and may explain the low 8.0 @xmath1 m planetary flux ratio ( see figure [ jonathan ] ) . an alternative explanation for the planet s low 3.6 @xmath1 m nightside emission is the presence of high - altitude silicate clouds on the cold nightside in or above the photosphere . the formation of an equilibrium silicate cloud is possible at the photospheric pressures ( @xmath92100 mbar ) probed on the nightside of wasp-14b by these observations ( e.g. * ? ? ? . however , it is expected that the presence of a thick cloud would suppress both the 3.6 and 4.5 @xmath1 m nightside fluxes from the planet , and the resulting planetary emission spectrum would resemble a blackbody with an effective temperature corresponding to that of the cloud tops . while the low 3.6 @xmath1 m nightside brightness temperature of @xmath242 k ( @xmath5 upper limit ) is consistent with a cold emitting layer , the two nightside band fluxes together are not consistent with a single blackbody spectrum . in this scenario , the high 4.5 @xmath1 m nightside emission ( corresponding to a brightness temperature of @xmath243 k ) could be explained by introducing an emitting layer of co in a warmer thermosphere that is situated above the cold cloud tops @xcite . however , it is unclear how a high - altitude temperature inversion might arise on the nightside , as there is no incident stellar irradiation and the efficiency of recirculation from the dayside should be relatively weak at low pressures . therefore , an enhanced c / o ratio in wasp-14b s atmosphere provides a more straightforward explanation for the observed differences between wasp-14b s 3.6 and 4.5 @xmath1 m phase curves . further observations of wasp-14b , possibly with _ hubble space telescope _ s wide field camera 3 , would provide important additional information to constrain wasp-14b s composition and either support or refute the high atmospheric c / o ratio scenario posited here for wasp-14b . we note that @xcite also suggested an enhanced c / o ratio to explain the differences seen between the 3.6 and 4.5 @xmath1 m phase - curve observations of hat - p-2b . additional phase - curve observations of hot jupiters may reveal similar trends and point to a fundamental piece of physics currently missing from exoplanet atmospheric models and/or planet formation theories . the sparc model utilized in this work does not readily accommodate non - solar c / o ratios . the exploration of the effects of different c / o ratios on the atmospheric dynamics of hot jupiters will be the topic of future work . we also compare the _ spitzer _ dayside and nightside emission with 1d models generated using the methods of @xcite with varying recirculation . these models assume local thermodynamic equilibrium , solar composition , and a plane - parallel atmosphere . a heat sink is included at depth ( between 0.003 and 0.6 bars ) to redistribute heat from the dayside to the nightside . these models also incorporate a generalized gray absorber at low pressures ( 0 to 0.03 bars ) , which is parametrized with an absorption coefficient , @xmath244 , with units of @xmath245 g@xmath163 . this absorber enhances the opacity of the planet s atmosphere at optical wavelengths , raising the local atmospheric temperature and producing a high - altitude temperature inversion . a second dimensionless parameter @xmath246 is used to specify the efficiency of energy redistribution , with @xmath247 indicating complete redistribution and @xmath248 signifying redistribution on the dayside only . m ( filled black circles ) with one - dimensional atmosphere model spectra following @xcite at the time of secondary eclipse and the time of transit , corresponding to the dayside and nightside of the planet . for the measured nightside 3.6 @xmath1 m emission , the @xmath5 upper limit is shown . solid colored lines indicate the predicted spectra for various choices of the parameters @xmath244 and @xmath246 , which represent the abundance of a generalized gray absorber in the upper atmosphere and the efficiency of energy redistribution , respectively . corresponding band - averaged points are overplotted in the same color . the black lines at the bottom represent the photometric band transmission profiles , in arbitrary units . the measured dayside 3.6 and 4.5 @xmath1 m planetary fluxes are most consistent with the model with @xmath249 and @xmath250 , indicating that wasp-14b has poor day - night recirculation and a moderate thermal inversion in the dayside atmosphere ; none of the models reproduces the low measured 8.0 @xmath1 m dayside emission . on the nightside , the measured nightside planetary fluxes in both the 3.6 and 4.5 @xmath1 m bands are not well - described by any of the models , which may point toward an enhanced atmospheric c / o ratio.,width=340 ] .,width=340 ] in figure [ burrows ] , we show the dayside and nightside spectra for various values of @xmath244 and @xmath246 and compare them with the measured relative planetary brightnesses in the two _ spitzer _ bands . figure [ burrowstp ] shows the corresponding dayside and nightside temperature - pressure profiles generated by the model . in these models the presence of the gray absorber does not affect day - night recirculation , so the nightside spectra depend only on the value of @xmath246 . we define the measured dayside brightness in each bandpass to be the measured secondary eclipse depth , while for the the nightside data points , we used the value of the best - fit relative planetary phase curve @xmath204 calculated at the mid - transit time in each bandpass . looking at the dayside spectra , we see that the @xmath249 and @xmath250 model spectrum comes closest to matching the measured data points at 3.6 and 4.5 @xmath1 m . this suggests that wasp-14b has poor day - night recirculation and a moderate thermal inversion in the dayside atmosphere . on the nightside , as in the sparc models , none of the models reproduce the low measured 3.6 @xmath1 m brightness , while the measured 4.5 @xmath1 m flux ratio is most consistent with the @xmath251 model . as discussed earlier in the context of the sparc models , this discrepancy is consistent with the hypothesis that wasp-14b might have an enhanced c / o ratio . we also note that large deviations from solar - like equilibrium chemical composition could yield a larger disparity in the pressures probed on the dayside and nightside than is accounted for in our models . specifically , one could be probing a deeper than expected pressure level on the nightside , where circulation is efficient ( high @xmath246 ) , while probing a higher - up ( lower pressure ) level on the dayside , where the circulation is less efficient ( low @xmath246 ) . this scenario is especially probable when there is a dayside temperature inversion , as our data suggest . finally , we compare the albedo and recirculation derived from our best - fit phase curves to other hot jupiters for which full - orbit thermal measurements have been obtained . following the methods described in @xcite , we use the measured eclipse depths and phase curve amplitudes to calculate the error - weighted dayside and nightside brightness temperatures , with corrections for the contamination due to reflected light : @xmath252 k and @xmath253 k. although these methods were developed for planets on circular orbits , the low eccentricity of wasp-14b places it in a regime for which the model is still a reasonable approximation . from these temperatures , we derive a bond albedo of @xmath254 ( @xmath2550.08 at @xmath142 ) and a day - night heat transport efficiency of @xmath256 , where the latter is defined such that @xmath257 means no heat recirculation to the nightside , and @xmath258 indicates complete redistribution . figure [ planets ] shows the location of wasp-14b in albedo - recirculation space along with six other exoplanets with measured thermal phase curves . s low day - night heat transport efficiency and high irradiation temperature are consistent with the general observed trend that highly - irradiated hot jupiters have poor heat recirculation @xcite . both wasp-14b and wasp-18b have much lower estimated albedos than those of other jovian mass planets with thermal phase curve measurements ; they are also both significantly more massive ( @xmath259 vs. @xmath260 ) . the low estimated albedos of these massive planets , implied by their high thermal emission , may instead be indicative of the detection of some amount of thermal radiation from the planet s interior in addition to the re - radiated stellar flux . a different cooling and/or migration history for these massive planets could result in an added contribution to the planetary emission from the deep atmosphere ; the age of the wasp-14 system is relatively young ( @xmath2551 gyr ; * ? ? ? * ) , so this additional internal flux may be due to significant residual heat of formation . in addition , the higher internal fluxes of these higher - mass planets may support stronger magnetic fields than on smaller planets , which may lead to stronger ohmic dissipation in their atmospheres ( e.g. , * ? ? ? * ; * ? ? ? * ) , thereby providing a source of additional emission on the dayside . bond albedo and recirculation efficiency confidence regions for planets with thermal phase curve observations , as calculated using the methods of @xcite . the color of the bounding curves indicate irradiation temperature . wasp-14b has intermediate day - night heat transport , like other hot jupiters of similar temperature . however , it has a very low bond albedo , like wasp-18b . both of these planets are significantly more massive than the other planets in the sample , suggesting that they may be emitting detectable heat from the deep atmosphere or interior processes.,width=340 ]

these same models tend to over - predict the nightside emission at 3.6 m , while under - predicting the nightside emission at 4.5 m . we propose that this discrepancy might be explained by an enhanced global c / o ratio . in addition , we find that the phase curves of wasp-14b ( ) are consistent with a much lower albedo than those of other jovian mass planets with thermal phase curve measurements , suggesting that it may be emitting detectable heat from the deep atmosphere or interior processes .

we present full - orbit phase curve observations of the eccentric ( ) transiting hot jupiter wasp-14b obtained in the 3.6 and 4.5 m bands using the _ spitzer space telescope_. we use two different methods for removing the intrapixel sensitivity effect and compare their efficacy in decoupling the instrumental noise . our measured secondary eclipse depths of and at 3.6 and 4.5 m , respectively , are both consistent with a blackbody temperature of k. we place a upper limit on the nightside flux at 3.6 m and find it to be of the dayside flux , corresponding to a brightness temperature of 1079 k. at 4.5 m , the minimum planet flux is of the maximum flux , corresponding to a brightness temperature of k. we compare our measured phase curves to the predictions of one - dimensional radiative transfer and three - dimensional general circulation models . we find that wasp-14b s measured dayside emission is consistent with a model atmosphere with equilibrium chemistry and a moderate temperature inversion . these same models tend to over - predict the nightside emission at 3.6 m , while under - predicting the nightside emission at 4.5 m . we propose that this discrepancy might be explained by an enhanced global c / o ratio . in addition , we find that the phase curves of wasp-14b ( ) are consistent with a much lower albedo than those of other jovian mass planets with thermal phase curve measurements , suggesting that it may be emitting detectable heat from the deep atmosphere or interior processes .

1505.03158

c

in this paper we present the first phase curve observations of the eccentric hot jupiter wasp-14b in the _ spitzer _ 3.6 and 4.5 @xmath1 m bandpasses . we compare two different techniques pixel mapping and pixel - level decorrelation for correcting the intrapixel sensitivity effect and find that the pixel mapping method yields lower residual scatter from the best - fit solution . this is likely due to the relatively large range of star positions on the pixel throughout the full - orbit observations that may make the intrapixel sensitivity effect less amenable to modeling through pixel - level decorrelation . we obtain best - fit secondary eclipse depths of @xmath2 and @xmath3 at 3.6 and 4.5 @xmath1 m , respectively , which are consistent with a single blackbody brightness temperature of @xmath4 k. these depths are in good agreement ( within @xmath142 ) with the ones reported by @xcite in their _ spitzer _ secondary eclipse analysis . combining the results of our global phase curve fits with previous radial velocity measurements , we derive updated values for orbital inclination , orbital eccentricity , longitude of pericenter , orbital semi - major axis , planet radius , and planet mass . we also combine our measured transit times with previously - published transit times to arrive at a more precise estimate of wasp-14b s orbital period : @xmath261 days . comparison of the measured dayside planetary emission with spectra generated from a one - dimensional radiative transfer model @xcite suggests relatively inefficient day - night heat recirculation and a moderate dayside temperature inversion . the relatively high dayside blackbody temperature provides additional support for the idea that the day - night circulation is inefficient . the flux maxima precede the secondary eclipses , consistent with other hot jupiter lightcurves and with predictions of general circulation models ( gcms ) , suggesting the possibility of equatorial superrotation on wasp-14b . we also utilize a three - dimensional gcm @xcite to generate theoretical light curves for an atmosphere in thermochemical equilibrium both with and without a dayside temperature inversion . we find that the measured amplitude and location of minimum / maximum flux in both bandpasses are more consistent with predictions from the model light curve with a dayside thermal inversion . meanwhile , the measured nightside planetary emission at 3.6 and 4.5 @xmath1 m is not adequately described by either the one - dimensional or the three - dimensional models . in particular , the very low 3.6 @xmath1 m nightside planetary flux indicates a significantly higher atmospheric opacity at that wavelength than is predicted by the models , which may point toward an enhanced c / o ratio . in the context of other planets with full - orbit thermal measurements , we find that wasp -14b fits the general trend that highly - irradiated hot jupiters have poor heat recirculation , while the derived bond albedo is very small ( @xmath2550.08 at @xmath142 ) and the planet s large mass might indicate that wasp-14b is emitting residual heat from its formation . the question of whether wasp-14b has an enhanced c / o ratio can be further addressed by obtaining measurements of the host star s c / o ratio . we note that wasp-14 has a near - solar metallicity ( @xmath262fe / h@xmath263 ; * ? ? ? * ) , so from a statistical standpoint , it is not expected to have a high c / o ratio @xcite . future work will explore how the assumed c / o ratio in the atmospheres of hot - jupiters like wasp-14b affects global circulation patterns and day / night temperature contrasts . the discrepancy between the model - predicted and measured nightside planetary flux underlines the need for further exploration of the available parameter space in both 1d and gcm models of hot jupiter atmospheres . assessing the effects of non - solar chemistry , and specifically different c / o ratios , will give us new insight into the interplay between various atmospheric properties and the resultant planetary emission . these studies promise to greatly enhance the ability of numerical models to explain features in the growing body of exoplanet phase curves . obtaining more infrared phase curves of massive planets and calculating their bond albedo will allow us to determine whether low bond albedo is strongly correlated with high planet mass , as is the case for wasp-14b and wasp-18b , and further consider the contribution of residual heat from formation in the overall emission of massive hot jupiters . a better understanding of the role of residual heat from formation in the flux of massive planets is also important for directly - imaged planets , as cooling curves are used to estimate the planetary mass based on the age of the system and the measured luminosity ( e.g. , * ? ? ? if we can determine whether current cooling models can reproduce the observed emission from wasp-14b , it would serve as an independent confirmation of the evolutionary models used in studies of directly imaged planets .

our measured secondary eclipse depths of and at 3.6 and 4.5 m , respectively , are both consistent with a blackbody temperature of k. we place a upper limit on the nightside flux at 3.6 m and find it to be of the dayside flux , corresponding to a brightness temperature of 1079 k. at 4.5 m , the minimum planet flux is of the maximum flux , corresponding to a brightness temperature of k. we compare our measured phase curves to the predictions of one - dimensional radiative transfer and three - dimensional general circulation models . we find that wasp-14b s measured dayside emission is consistent with a model atmosphere with equilibrium chemistry and a moderate temperature inversion .

we present full - orbit phase curve observations of the eccentric ( ) transiting hot jupiter wasp-14b obtained in the 3.6 and 4.5 m bands using the _ spitzer space telescope_. we use two different methods for removing the intrapixel sensitivity effect and compare their efficacy in decoupling the instrumental noise . our measured secondary eclipse depths of and at 3.6 and 4.5 m , respectively , are both consistent with a blackbody temperature of k. we place a upper limit on the nightside flux at 3.6 m and find it to be of the dayside flux , corresponding to a brightness temperature of 1079 k. at 4.5 m , the minimum planet flux is of the maximum flux , corresponding to a brightness temperature of k. we compare our measured phase curves to the predictions of one - dimensional radiative transfer and three - dimensional general circulation models . we find that wasp-14b s measured dayside emission is consistent with a model atmosphere with equilibrium chemistry and a moderate temperature inversion . these same models tend to over - predict the nightside emission at 3.6 m , while under - predicting the nightside emission at 4.5 m . we propose that this discrepancy might be explained by an enhanced global c / o ratio . in addition , we find that the phase curves of wasp-14b ( ) are consistent with a much lower albedo than those of other jovian mass planets with thermal phase curve measurements , suggesting that it may be emitting detectable heat from the deep atmosphere or interior processes .

astro-ph0003085

i

clusters of galaxies , by virtue of being the largest known virialized objects , are important probes of large scale structure and can be used to test cosmological models . rich clusters are extremely massive , @xmath1@xmath2 , as indicated by the presence of strongly gravitationally lensed background galaxies and by the deep gravitational potential necessary to explain both the large velocity dispersion ( @xmath3 1000 km s@xmath4 ) in the member galaxies and the high measured temperature ( @xmath5 kev ) of the ionized intracluster gas . dynamical mechanisms for segregating baryonic matter from dark matter on these mass scales are difficult to reconcile with observations and standard cosmological models , and so within the virial radius the mass composition of clusters is expected to reflect the universal mass composition . under the fair sample hypothesis , a cluster s gas mass fraction , which is a lower limit to the its baryonic mass fraction , is then a lower limit to the universal baryon fraction , i.e. , @xmath6 . the luminous baryonic content of galaxy clusters is mainly contained in the gaseous intracluster medium ( icm ) . the gas mass is nearly an order of magnitude larger than the mass in optically observed galaxies ( , white 1993 , forman & jones 1982 ) . hence , the gas mass is not only a lower limit to the cluster s baryonic mass , it is a reasonable estimate of it . the intracluster medium has largely been studied through observations of its x - ray emission . the icm is hot , with electron temperatures , @xmath7 , from @xmath15 to 15 kev ; rarefied , with peak electron number densities of @xmath8 @xmath9 ; and cools slowly ( @xmath10 ) , mainly via thermal bremsstrahlung in the x - ray band . the x - ray surface brightness is proportional to the emission measure , @xmath11 , where the integration is along the line of sight , and so , under simplifying assumptions , the gas mass can be calculated from an x - ray image deprojection and the measured gas temperature . since the sound crossing time of the cluster gas is much less than the dynamical time , one may reasonably assume that , in the absence of a recent merger , the cluster gas is relaxed in the cluster s potential . the total binding mass can be extracted from the gas density and temperature distribution under this assumption . a significant body of work exists in which the gas mass fraction , @xmath12 , is measured in this way , with @xmath12 measurements out to radii of 1 mpc or more ( white & fabian 1995 ; david 1995 ; neumann & bohringer , 1997 ; squires 1997 ; mohr , mathiesen & evrard 1999 ) . the mean cluster gas mass fraction within approximately the virial radius was calculated in mohr ( 1999 ) to be ( 0.0749 @xmath13 . here , and throughout the paper , we assume the value of the hubble constant to be @xmath14 km s@xmath4 mpc@xmath4 . to derive the gas mass fraction from x - ray imaging data , one is required to deproject the surface brightness into a model for the density distribution . as the x - ray emission is proportional to the square of the gas density , the gas mass measurement can be biased by clumped , multi - phase gas , should it be present . also , the emission from the cores of relaxed clusters may be dominated by cooling flows , which complicate the interpretation of the x - ray data and may bias the result strongly if not taken into account ( allen 1998 ; mohr 1999 ) . in addition , the x - ray surface brightness is diminished in proportion to its distance ; @xmath15 , where @xmath16 is the redshift of the cluster , neglecting experiment - specific k - corrections , and so it becomes increasingly difficult to make sensitive x - ray measurements of the icm as the cluster redshift increases . we present a scheme for measuring the gas mass fractions with the sunyaev - zeldovich effect which is different from the x - ray method in a number of ways , and also provides an independent measurement of @xmath12 . the sunyaev - zeldovich ( sz ) effect is a spectral distortion of cosmic microwave background ( cmb ) radiation due to scattering of cmb photons by hot plasma ( sunyaev & zeldovich 1970 ) . the sz effect can be detected significantly in galaxy clusters , where the ionized intracluster gas serves as the scattering medium . a small fraction , @xmath17 , of cmb photons are inverse - compton scattered and , on average , gain energy . at frequencies less than about 218 ghz , the intensity of the cmb radiation is diminished as compared to the unscattered cmb , and the sz effect is manifested as a brightness temperature decrement towards the cluster . this decrement , @xmath18 , has a magnitude proportional to the total number of scatterers , weighted by their associated temperature , @xmath19 , where @xmath20 is the number density of electrons , @xmath7 is the electron temperature , @xmath21 is the temperature of the cmb , and the integration is again along the line of sight . note that this is simply proportional to the integrated electron pressure . also , the magnitude of the sz decrement is independent of redshift , so as the long as the cluster is resolved ( the experiment s characteristic beamsize is not larger than the angle subtended by the cluster ) , the sz effect can be measured towards arbitrarily distant clusters . a cluster s gas mass is directly proportional to its integrated sz effect if the gas is isothermal . so under the isothermality condition , an image deprojection is not strictly required to obtain the gas mass . the cluster s gas mass fraction can be calculated by comparing the integrated sz decrement , in effect a surface gas mass , to the total cluster mass in the same volume . the total mass can be measured with strong or weak gravitational lensing , for example . the sz images may also be deprojected to infer the three - dimensional gas mass and the hse mass . since the sz decrement is directly propotional to the electron density , the sz image deprojection will not be affected strongly by clumped gas . thus , the cluster s gas mass fraction can then be measured as a function of cluster radius as well . recent cluster gas mass fraction measurements from sz effect observations are presented in myers ( 1997 ) . in this work , the integrated sz effect is measured using a single radio dish operating at centimeter wavelengths . the integrated sz effect is used to normalize a model for the gas density from published x - ray analyses , and this gas mass is compared to the published total masses to determine the gas mass fraction . for three nearby clusters , a2142 , a2256 and the coma cluster , myers find a gas mass fraction of @xmath22 at radii of 1 - 1.5 @xmath23 mpc ; for the cluster abell 478 , they report a gas mass fraction of @xmath24 . in this work , we describe a method to calculate cluster gas mass fractions from interferometric sz observations . here , the shape parameters are derived directly from the sz dataset rather than from an x - ray image . we apply this method to the sz effect measurements towards the cluster abell 370 , which were made as part of an sz survey of distant clusters , the first results of which were reported in carlstrom , joy & grego ( 1996 ) , and are further reported in carlstrom ( 1997 ) . we choose this primarily because it has been studied at optical and x - ray wavelengths , and so allows a comparison of the sz data with other observations . upon detailed investigation , it is apparent that this cluster is one of the most difficult in our sample to analyze , with significant ellipticity and complicated optical and x - ray structure ; as such , it serves as a test of the gas mass fraction analysis method , which we plan to use on a large sample of clusters . with the interferometric sz measurements , complemented by observations at other wavelengths , we measure the cluster s gas mass fraction in two ways first , we calculate the surface gas mass from the sz measurements and the surface total mass from strong gravitational lensing observations and models . second , we measure the gas mass fraction in a manner similar to x - ray analyses . the gas mass is inferred from a deprojected model ; the total mass is determined from the spatial distribution of the gas under the isothermal hydrostatic equilibrium ( hse ) assumption . we test the assumptions made in the hse analysis by comparing the total cluster masses derived in the two methods . the optical and x - ray observations of this cluster are discussed in section [ sec : optxray ] , and the sz observations are discussed in section [ sec : szobs ] . the method for modeling the sz data is presented in section [ sec : model ] , and the gas mass fraction results and the systematic uncertainties are discussed in section [ sec : analysis ] . the cosmological implications of the results and plans for future work are discussed in section [ sec : discussion ] .

these measurements , which directly probe the pressure of the cluster s gas , show the gas distribution to be strongly aspherical , as do the x - ray and gravitational lensing observations . we calculate the cluster s gas mass fraction in two ways . we first compare the gas mass derived from the sz measurements to the lensing - derived gravitational mass near the critical lensing radius . we also calculate the gas mass fraction from the sz data by deprojecting the three - dimensional gas density distribution and deriving the total mass under the assumption that the gas is in hydrostatic equilibrium ( hse ) . we test the assumptions in the hse method by comparing the total cluster mass implied by the two methods and find that they agree within the errors of the measurement .

we present interferometric measurements of the sunyaev - zeldovich ( sz ) effect towards the galaxy cluster abell 370 . these measurements , which directly probe the pressure of the cluster s gas , show the gas distribution to be strongly aspherical , as do the x - ray and gravitational lensing observations . we calculate the cluster s gas mass fraction in two ways . we first compare the gas mass derived from the sz measurements to the lensing - derived gravitational mass near the critical lensing radius . we also calculate the gas mass fraction from the sz data by deprojecting the three - dimensional gas density distribution and deriving the total mass under the assumption that the gas is in hydrostatic equilibrium ( hse ) . we test the assumptions in the hse method by comparing the total cluster mass implied by the two methods and find that they agree within the errors of the measurement . we discuss the possible systematic errors in the gas mass fraction measurement and the constraints it places on the matter density parameter , . 0

astro-ph0307265

c

a physico - chemical investigation of the symmetrical pairs of structures rim , inner and outer knots , and jetlike systems connecting the latter in ngc 7009 is presented . this study , the most extensive ( eight individual regions along the major axis ) , better resolved ( 1 arcsec spatial resolution within the central 1 arcmin ) and complete to date ( including all diagnosis from available optical lines ) , has revealed a clear and coherent pattern of physical , excitation , and chemical characteristics through the nebula : 1 ) the electron temperature , both for low- and high- excitation species , is remarkably constant ; 2 ) electron densities are similar for both the jetlike structures and the outer knots , but they are roughly one - third of those found in the pair of inner knots and the rim ; 3 ) no sign of shock excitation is found for any of the microstructures or the rim ; and 4 ) a notable chemical uniformity is found for the eight regions studied , with the exception of a marginal , moderate ( @xmath9 2 ) enhancement of nitrogen at the outernmost knots . the origin of the system of microstructures in ngc 7009 is discussed in the light of its physico - chemical parameters and the available theoretical models , but none of these appears able to account for both the lack of a strong density contrast between the outer knots and jetlike structures , and the absence of shocks in them . more than 200 years after its discovery by herschel , the saturn nebula is still challenging our comprehension .

we present long - slit optical spectra along the major axis of the planetary nebula ngc 7009 . these data allow us to discuss the physical , excitation and chemical properties of all the morphological components of the nebula , including its remarkable systems of knots and jets . i ) _ the electron temperature throughout the nebula is remarkably constant , = k ; _ ii ) _ the bright inner rim and inner pair of knots have similar densities of , whereas a much lower density of 1500 is derived for the outer knots as well as for the jets ; _ iii ) _ all the regions ( rim , inner knots , jets and outer knots ) are mainly radiatively excited ; and _ iv ) _ there are no clear abundance changes across the nebula for he , o , ne , or s. there is a marginal evidence for an overabundance of nitrogen in the outer knots ( ansae ) , but the inner ones ( caps ) and the rim have similar n / h values that are at variance with previous results . our data are compared to the predictions of theoretical models , from which we conclude that the knots at the head of the jets are not matter accumulated during the jet expansion through the circumstellar medium , neither can their origin be explained by the proposed hd or mhd interacting - wind models for the formation of jets / ansae , since the densities as well as the main excitation mechanisms of the knots , disagree with model predictions .

we present long - slit optical spectra along the major axis of the planetary nebula ngc 7009 . these data allow us to discuss the physical , excitation and chemical properties of all the morphological components of the nebula , including its remarkable systems of knots and jets . the main results of this analysis are the following : _ i ) _ the electron temperature throughout the nebula is remarkably constant , = k ; _ ii ) _ the bright inner rim and inner pair of knots have similar densities of , whereas a much lower density of 1500 is derived for the outer knots as well as for the jets ; _ iii ) _ all the regions ( rim , inner knots , jets and outer knots ) are mainly radiatively excited ; and _ iv ) _ there are no clear abundance changes across the nebula for he , o , ne , or s. there is a marginal evidence for an overabundance of nitrogen in the outer knots ( ansae ) , but the inner ones ( caps ) and the rim have similar n / h values that are at variance with previous results . our data are compared to the predictions of theoretical models , from which we conclude that the knots at the head of the jets are not matter accumulated during the jet expansion through the circumstellar medium , neither can their origin be explained by the proposed hd or mhd interacting - wind models for the formation of jets / ansae , since the densities as well as the main excitation mechanisms of the knots , disagree with model predictions .

astro-ph0002033

c

our observations of nvss 2146 + 82 clearly show that it is an unusually large fr ii radio galaxy . its angular distance from the north lobe to the south lobe gives an unusually large extent of @xmath96 . for our assumed cosmology and our measured redshift of @xmath0 , the linear extent of the radio structure is 4@xmath2 mpc , placing it in the giant radio galaxy ( grg ) class , which we define as sources larger than 2@xmath2 mpc . nvss 2146 + 82 is therefore the second largest fr ii known , surpassed only by 3c236 which is @xmath16@xmath2 mpc in extent . fr ii galaxies of this size are extremely rare ; a literature search by @xcite of 540 fr iis contains only 27 objects with sizes greater than 1@xmath2 mpc . of this sample of 27 large fr iis , only 5 are larger than 2@xmath2 mpc . for comparison , the other known giant radio sources are shown in table [ table : giants ] . the log radio luminosity of nvss 2146 + 82 at 1.4 ghz is 25.69 , in the middle of the range for giant radio sources . it remains unclear if there are fundamental differences between grgs and `` normal '' radio galaxies . the relative paucity of known grgs may be in part due to observational selection effects in past radio surveys . an alternative reason for the rarity of giant radio galaxies may be that the physical conditions necessary for the creation of a grg are uncommon in the universe . although the similarity between nvss 2146 + 82 and other fr iis suggests that it is a typical fr ii radio galaxy at the extreme end of the size distribution , a study of a complete sample of radio galaxies that includes grgs will have to be made to determine if grgs are part of a continuous distribution in size of normal radio galaxies or if there are fundamental differences between grgs and smaller fr iis . if the usual equipartition assumptions are made , then it is possible to estimate the magnetic field strength and pressure in the lobes . assuming that the observed spectral index is maintained from 10 mhz to 100 ghz , that there are equal energies in the radiating electrons and other particles , and that the filling factor is unity , the derived magnetic field is b@xmath97 gauss and p@xmath98 @xmath99k for the hot spots . at the midpoint of the lobes these values are b@xmath100 gauss and p@xmath101 @xmath99k . at this redshift , the 3 k microwave background has an equivalent magnetic field of 4.2@xmath102 gauss so the energy loss in the lobes should be dominated by inverse compton scattering of this background , and the time for the electrons radiating at 1400 mhz to lose half of their energy will be @xmath103 years . the mean faraday rotation of @xmath24 @xmath104 rad m@xmath15 shown in figure [ fig : rm ] is consistent with the results of @xcite for other extragalactic sources seen through this region of the galaxy ( @xmath105 ) . it is therefore likely that the rotation measure screen seen in figure [ fig : rm ] is primarily the foreground screen of our galaxy . the low apparent rotation measure and the smoothness of the polarization structure shown in figure [ fig : polarization ] suggests that the magnetic field in this source is well ordered . the field configuration is entirely typical of older extended fr ii sources , with the e vectors lying approximately perpendicular to the ridge line of the radio emission in most features . we note that the greater variance and evidence for organized structure in the faraday rotation of the southern lobe is the opposite of what would be expected if the jet sidedness were due to doppler favoritism and the faraday rotating medium were local to the source . we think it more likely that the faraday rotation structure arises along the line of sight in our galaxy . the spectral index variations shown in figure [ fig : si ] indicate that there are regions @xmath106 back towards c from the brightest region in each lobe that have unusually flat spectra ( @xmath23 -0.3 ) , flatter even than the hot spots . the only extended synchrotron sources known with spectra this flat are a few galactic supernova remnants ( @xcite ) . the spectral index structure in nvss 2146 + 82 is unlike the systematic steepening of the spectrum away from the hot spots that is usually interpreted as an effect of spectral aging in extended lobes . in such interpretations , electrons are presumed to be injected into a high field region in or around the hot spots , and their energy spectrum steepens with distance as they diffuse into lower field regions of the extended lobes . clearly no such interpretation can be made here . these flatter spectrum regions occur in the transition zone from the featureless parts of the lobes ( closer to the core ) to the parts near the regions of enhanced emission that contain significant filamentary structure . the anomalous regions are near the midline of the lobes ; the southern region is centered on the path of the jet and the northern region is at one end of a prominent filament ( the path of the jet is uncertain ) . the relative symmetry of the flatter spectrum regions of the lobes suggests that they might be produced by an intrinsic property of the source , such as a variable spectral index in the injection spectrum of the relativistic electrons from the jet , rather than local environmental effects . if the magnetic field has values near those estimated by the equipartition calculations given above , then the energy loss of the radiating electrons is dominated by inverse compton scattering against the cosmic microwave background . in the low density , low magnetic fields in these lobes , the aging effects will be slow and the history of a variable electron spectrum could be maintained along the length of the lobe . there are three size scales on which symmetries appear or change in the radio structure : the first is @xmath107 kpc . the jets appear to become symmetric on this scale but are asymmetric on smaller scales . if the j2 and k components ( figure 4 ) are symmetric features in the jet and counterjet , any doppler boosting from relativistic motion must have disappeared by this point in the jet . the second scale is @xmath108 kpc . on this scale , there is a dramatic brightening of both lobes . the third scale is @xmath109 kpc . at this distance , the lobes become even brighter and strong filamentary structure appears . this is the distance at which regions of spectral anomaly appear in the extended emission . the largest scale symmetries thus suggest a symmetric overall environment , apart from the slight non - collinearity ( c - symmetry ) of the structure . the small scale brightness asymmetries of the jet and counterjet might be attributed to doppler boosting and dimming by relativistic motion which effectively disappears by @xmath110 kpc , i.e. on a scale more typical of a `` non - giant '' fr ii source . we reiterate however that the small asymmetry in rotation measure dispersion ( variance ) between the lobes is opposite in sign to that expected on this interpretation . this asymmetry seems more likely to reflect an intrinsic asymmetry ( or gradient ) in the foreground magnetoionic medium . one possibility for the origin of grgs is that they are otherwise normal fr ii sources that reside in extremely low density gaseous environments . the environments in which radio galaxies reside have been studied in depth ( e.g. @xcite ; @xcite ; @xcite ; @xcite ; @xcite ; @xcite ) because the gas density and pressure in the host galaxy s ism , any intracluster medium , and the igm are at least partly responsible for determining the resulting radio morphology . an intriguing result of recent studies ( @xcite ; @xcite , @xcite ) is that fr ii galaxies are found in a range of cluster richnesses at moderate redshifts , but they are only found in poor to very poor groups at low redshift . the `` richness '' of the cluster associated with a radio galaxy can be estimated in a statistical sense in the absence of redshift data on nearby galaxies . allington - smith et al . ( 1993 ) define the richness parameter @xmath75 as the number of galaxies within a projected radius of 500 kpc and with @xmath111 assuming the same redshift as the agn . the number counts are corrected for contamination by foreground and background galaxies by subtracting number counts from a field offset from the radio galaxy . zirbel ( 1997 ) gives a conversion of @xmath75 to abell class as @xmath112 . with this conversion , the thresholds for abell classes 0 and 1 are @xmath113 and 26 respectively . using this richness estimation technique , zirbel ( 1997 ) found that of a sample of 29 low redshift ( @xmath114 ) fr iis : ( 1 ) 41% of the sample of low @xmath93 fr iis reside in very poor groups ( @xmath115 ) , and ( 2 ) more importantly , no low redshift fr ii was found in a rich group with @xmath116 . based on the results given in 3.5 , nvss 2146 + 82 appears to reside in a group with an anomalously high galaxy richness compared to other low redshift fr iis . although the galaxy counts from the field surrounding nvss 2146 + 82 were not calculated identically to those of zirbel ( 1997 ) , the value of @xmath75 is likely @xmath117 for nvss 2146 + 82 . the upper limit on the cluster x - ray emission is consistent with the nvss 2146 + 82 group being at the low end of the x - ray luminosity distribution for poor clusters . @xcite found that in a comparison of low redshift clusters with and without fr ii sources , clusters that contained fr iis were underluminous in x - rays compared to clusters without fr iis . although the cluster surrounding nvss 2146 + 82 may be abell class 0 , its lack of associated x - ray gas suggests that the pressure in the surrounding medium is low enough for a giant radio source to form with little disruption of the fr ii jet . curiously , several other grgs listed in table [ table : giants ] also appear to lie in regions with overdensities of nearby galaxies . the grg 0503 - 286 appears to lie in a group of 30 or so galaxies ( @xcite ) . these companions are concentrated to the northeast of the host galaxy of 0503 - 286 , and may have caused the asymmetric appearance of the northern lobe of the radio structure . overdensities of nearby galaxies are also reported for 1358 + 305 ( @xcite ) and 8c 0821 + 695 ( @xcite ) ; however , in both cases there is no spectroscopic confirmation of the redshifts of the candidate cluster galaxies . in a recent study of the optical and x - ray environments of radio galaxies , @xcite find that for a sample of fr i sources , all have extended x - ray emission and overdensities of optical galaxies . however of their sample of seven fr ii sources , none have overdensities of optical galaxies or extended x - ray emission except for the grg da240 , which has no extended x - ray emission but does have a marginally significant excess of optical companions . perhaps for at least some of the grg population , the presence of the host galaxy in an optically rich group with little associated x - ray gas is related to the formation or evolution of the radio source ?

the radio structure is normal for an fr ii source except for its large size and regions in the lobes with unusually flat radio spectra . this object is therefore the second largest fr ii known ( 3c 236 is mpc ) . several other giant radio galaxies have been found in regions with overdensities of nearby galaxies , and a separate study has shown that groups containing fr iis are underluminous in x - rays compared to groups without radio sources . we speculate that the presence of the host galaxy in an optically rich group of galaxies that is underluminous in x - rays may be related to the giant radio galaxy phenomenon .

we present multi - frequency vla , multicolor ccd imaging , optical spectroscopy , and _ rosat _ hri observations of the giant fr ii radio galaxy nvss 2146 + 82 . this galaxy , which was discovered by the nrao vla sky survey ( nvss ) , has an angular extent of nearly 20 from lobe to lobe . the radio structure is normal for an fr ii source except for its large size and regions in the lobes with unusually flat radio spectra . our spectroscopy indicates that the optical counterpart of the radio core is at a redshift of , so the linear size of the radio structure is mpc , . this object is therefore the second largest fr ii known ( 3c 236 is mpc ) . optical imaging of the field surrounding the host galaxy reveals an excess number of candidate galaxy cluster members above the number typically found in the field surrounding a giant radio galaxy . wiyn hydra spectra of a sample of the candidate cluster members reveal that six share the same redshift as nvss 2146 + 82 , indicating the presence of at least a `` rich group '' containing the fr ii host galaxy . _ rosat _ hri observations of nvss 2146 + 82 place upper limits on the x - ray flux of ergs s for any hot igm and ergs s for an x - ray agn , thereby limiting any x - ray emission at the distance of the radio galaxy to that typical of a poor group or weak agn . several other giant radio galaxies have been found in regions with overdensities of nearby galaxies , and a separate study has shown that groups containing fr iis are underluminous in x - rays compared to groups without radio sources . we speculate that the presence of the host galaxy in an optically rich group of galaxies that is underluminous in x - rays may be related to the giant radio galaxy phenomenon .

1509.07474

r

to search for possible counterparts of 3fgl j2039.6@xmath15618 in our multi - wavelength observations , we used as a reference its recent 3fgl position ( acero et al . 2015 ) : @xmath29 and @xmath30 ( j2000 ) . its associated 95% confidence position error ellipse has semi - major and semi - minor axis of 2.6 and 2.4 , respectively , and a position angle of @xmath31 , measured east of north . we started from our _ xmm - newton _ observations to find potential x - ray counterparts to 3fgl j2039.6@xmath15618 . then , we used our multi - wavelength data base to single out those that are most likely associated with this @xmath0-ray source . in particular , since we expect that 3fgl j2039.6@xmath15618 is a binary msp , we focused our analysis on x - ray sources that show variability and/or have variable optical counterparts , possibly featuring periodic flux modulations . for our x - ray analysis , we selected only 0@xmath14 pattern events from the pn and 0@xmath112 from the two mos detectors with the default flag _ mask_. the source detection in the 0.310 kev energy range was run simultaneously on the event lists of each of the epic - pn and mos detectors using a maximum likelihood fitting with the sas task edetect_chain invoking other sas tools to produce background , sensitivity , and vignetting - corrected exposure maps . the final source list includes 90 x - ray sources from both the pn and mos detectors , with a combined pn+mos detection likelihood greater than 10 , corresponding to a significance above @xmath32 . figure [ xmm - image ] shows the 0.310 kev exposure - corrected _ xmm - newton _ fov obtained combining the images of the epic - pn and mos detectors . we focused our analysis on the 16 x - ray sources detected within , or close to , the 95% confidence position error ellipse of 3fgl j2039.6@xmath15618 . we summarized the positions , spectral parameters , fluxes , and variability indices of these sources in table [ tab1 ] . for each epic detector we extracted the source photons using an extraction radius of 20 , while we extracted background photons from source - free regions in the same ccd chip as the source , with radii of 50120 . for each detector , we used the sas task specgroup to rebin all the extracted spectra and have at least 25 counts for each background - subtracted spectral channel and generated ad hoc response matrices and ancillary files using the sas tasks rmfgen and arfgen . for each source , we fitted simultaneously the pn and mos spectra using xspec v12.8 , forcing the same set of parameters and considering three different spectral models : a _ power - law _ ( pl ) , well suited for both agn and pulsars , an _ apec _ ( ap ) for stellar coronae , and a _ black - body _ ( bb ) for the pulsar thermal component . in all cases , the hydrogen column density @xmath33 was left as a free parameter . for each emission model we computed the 90% confidence level error on the spectral parameters . when the best - fit @xmath33 values were comparable to zero , we assumed the measured uncertainties to determine the @xmath34 confidence level upper limit . spectra with very low counts were fitted after fixing the @xmath33 to the estimated value along the line of sight ( @xmath35 @xmath5 ; dickey & lockman 1990 ) , or fixing either the photon index or the temperature to typical values , i.e. @xmath36 and @xmath37 kev or @xmath38 kev in case of an ap and a bb model , respectively . as shown in table [ tab1 ] , only source 3 and 11 , the two brightest x - ray sources in our sample , were best fitted by a simple pl model , with a @xmath39=52.32 ( 42 degrees of freedom , d.o.f . ) for the former and @xmath39=16.06 ( 22 d.o.f . ) for the latter . for the remaining 13 sources , at least two different models were required to obtain an acceptable fit with null hypothesis probability @xmath40 0.01 . only for source 88 it was not possible to obtain acceptable results with any of the selected spectral models . indeed , this source is the faintest in our sample and is likely spurious . figure [ spec_src3 ] shows the binned spectrum of source 3 extracted simultaneously from each of the epic detectors , together with the best - fit pl model . since most msps are characterized by a significant thermal component to their x - ray spectra , we tried to fit the spectra of source 3 and source 11 with an absorbed bb plus pl model . this improved the accuracy of the fit only for source 3 , with a @xmath39=34.9 ( 40 d.o.f . ) . from the f - test ( bevington 1969 ) , we computed a 0.0003 probability that adding a thermal component to the model would produce a chance improvement to the fit . since this probability corresponds to a @xmath103.6@xmath41 significance only , hereafter we ignored the absorbed bb plus pl spectral model . since for most x - ray sources the measured counts are too few to clearly discriminate among different spectral models , we checked whether we could extract qualitative spectral information from an hardness ratio ( hr ) analysis ( marelli et al . however , we found that the observed hrs are compatible with different spectral models and , therefore , are not constraining . in order to detect possible time variability during the _ xmm - newton _ observation , we generated standard light curves from the pn - data for all the 16 x - ray sources in table 1 . starting from the source and background regions described in section [ spectra ] , we extracted source+background and background light curves , respectively , with the sas task evselect and combined them into a background - subtracted light curve with the task epiclccorr . this task also corrects the time series for vignetting , bad pixels , chip gaps , quantum efficiency , dead time , exposure and good time intervals . for each source we generated a light curve with time binning of 2500 s , or multiple of this value , to have at least 25 counts per bin and we ran a @xmath39 test to evaluate the variability significance . only source 3 is characterized by a significant variability during the observation ( @xmath42 , with 16 d.o.f . ) , with a chance probability of @xmath43 ( @xmath44 ) . after combining the data from all the three epic cameras the source 3 light curve shows a more apparent variability ( figure [ lc_src3 ] , left ) , with a chance probability of @xmath45 , whereas the other x - ray still show no evidence of significant variability . the source 3 light curve also hints at a possibly periodic modulation . we converted photon arrival times to the solar system barycentric dynamical time ( tbd ) with the sas task barycen and used the ftool task efsearch to find the best period in the light curve through a maximum @xmath39 test . we folded the light curve with periods ranging from 100 to 43000 s , the latter comparable to the length of the _ xmm - newton _ observation . we found the best - fit period at 0.2245@xmath20.0081 d , where the period uncertainty was obtained following leahy ( 1987 ) . the corresponding @xmath39 of 104.5 ( 9 d.o.f . ) gives a chance probability of @xmath46 , accounting for the number of trials , and makes the periodicity statistically significant ( @xmath47 ) . the presence of a periodic signal at the corresponding frequency of @xmath48 hz was independently confirmed by the power spectrum produced with the ftool powspec . we note that the best - fit x - ray period of source 3 is comparable to about half the length of the _ xmm - newton _ observation , so that the observed periodicity might be spurious . we examined the light curves of other comparably bright x - ray sources detected in the whole _ xmm - newton _ fov and found that none of them showed evidence of periodicity at any time scales . nonetheless , the fact that the length of the _ xmm - newton _ observation only covers @xmath10 2.3 cycles , prevents us to firmly claim that source 3 is periodic . the x - ray light curve folded at the best - fit period ( figure [ lc_src3 ] , right ) is characterised by two peaks separated in phase by 0.31@xmath20.04 . therefore , it can not be described by a simple sinusoidal or gaussian model , with a null hypothesis probability lower than @xmath49 . we checked whether the folded x - ray light curve of source 3 varied as a function of the energy and whether the x - ray spectrum changed as a function of the phase . in both cases , however , the available statistics is not sufficient to highlight significant differences in the energy - resolved light curves and the phase - resolved spectra . we looked for archival x - ray images of the 3fgl j2039.6@xmath15618 field to check for long - term variability of source 3 . the field was serendipitously observed with the x - ray imaging spectrometer ( xis ) of _ suzaku _ ( mitsuda et al . 2007 ) on october 28 , 2010 for a total exposure time of 21.5 ks ( obsid 705028010 ) . we extracted source counts from a circle of radius 13 around the best _ xmm - newton _ coordinates of source 3 and background counts from a nearby , source - free 2-radius circle using the heasoft(v.6.16 ) tool xselect and summed the spectra from all the xis cameras with the mathpha , addarf and addrmf tools . we obtained 350 counts , of which @xmath1050% are from the source . a fit with a pl gives a null hypothesis probability of 0.06 ( 4 d.o.f . ) , with @xmath50 @xmath5 ( 90% upper limit ) , photon index @xmath51=1.3@xmath20.4 and an unabsorbed flux in the 0.310 kev energy range of 1.7@xmath52 @xmath53 erg @xmath5 s@xmath7 , fully compatible with the _ xmm - newton _ results . the _ xmm - newton _ count - rate and spectral parameters ( table [ tab1 ] ) are also compatible with the non - detection above the 3@xmath41 threshold ( @xmath10 1.05 @xmath53 erg @xmath5 s@xmath7 ) of source 3 in the short _ swift_/xrt images of takeuchi et al . ( 2013 ) , taken in 2010 and 2011 . therefore , we find no evidence of variability of source 3 on time scales of three years . we cross - matched the positions of all the 16 _ xmm - newton _ sources in table 1 with the source catalogues obtained from the grond observations . we performed the source detection on the single - band grond exposures using the starfind tool in iraf , matched the source catalogs over the different observations , and checked for variable sources against the median of all observations . object photometry was computed using the task daophot in iraf and the airmass correction was applied using the standard atmospheric extinction coefficients for the la silla observatory . for the cross - match we used a radius obtained by combining the statistical @xmath54 uncertainty on the x - ray source centroid plus the 90% confidence level systematic error associated with the absolute accuracy of the _ xmm - newton _ aspect solution , which is 15 per coordinate . the uncertainty on the absolute astrometry of the grond images ( 03 ) is much lower than the _ xmm - newton _ one , and is accounted for by our choice of the matching radius . there are only six _ xmm - newton _ sources ( source 3 , 13 , 22 , 24 , 40 , 76 ) with at least a candidate optical or near - ir counterpart in the grond data ( figure [ grond - image ] ) . we also cross - correlated the _ xmm - newton _ source list with the vista , om , and uvot source catalogues . the source detection and photometry in the vista images were carried out as a part of the casu pipeline ( sectn . [ opt_uv ] ) . for the om images , the source detection and photometry were carried out with the sas tasks omdetect and ommag , respectively , and for the uvot images with the heasoft taks uvotdetect and uvotsource . as before , the matching radius accounted for the uncertainty on the absolute astrometry of the used source catalogues , i.e. @xmath55 ( vista ; emerson et al . 2004 ) , 05 ( uvot ; breeveld et al . 2010 ) , and 07 ( om ; page et al . the cross - correlations with these catalogues provided additional near - ir , and near - uv magnitudes for some of the grond sources and unveiled candidate counterparts for source 11 , 19 , 29 , 60 , 88 . we found no counterparts in the om / uvm2 filter , whereas only source 3 was detected in the uvot / uvw2 images . the optical , near - uv , and near - ir magnitudes of the candidate counterparts to the _ xmm - newton _ sources are summarised in table 2 . only for the candidate counterparts to source 3 , 40 , and 76 we have an adequate spectral coverage in at least the optical and near - ir . among the six _ xmm - newton _ sources with a possible grond counterpart , only source 3 is associated with a clearly variable object ( @xmath56 , with 51 d.o.f . ) . figure [ grond - lc ] ( left ) shows the multi - band light curves of this object for the three nights spanned by the grond observations . as seen , the light curves seem modulated , with an amplitude of @xmath100.4 magnitudes in the g@xmath19 band . in particular , the modulation seems to be periodic and feature a double - peaked profile ( night 1 ) with the two peaks only partially seen in night 2 and 3 , likely owing to the different sampling of the light curve . this modulation is also seen in the r@xmath19 , i@xmath19 , and z@xmath19 light curves , with both shape and amplitudes similar to the g@xmath19 one , and is also recognised in the j and h - band light curves , and very marginally in the k - band one . this suggests that the observed modulation is real and not due , for instance , to possible problems with the photometry in a given filter . as a check , for all filters we extracted the light curves of several stars of comparable brightness detected in the grond fov but found no evidence of such a modulation this confirms that it is not due to random effects , such as variations in the sky conditions ( transparency , background , moon illumination ) , or systematic effects , such as variations in the encircled flux due to the fixed size of the photometry aperture with respect to the seeing disk . furthermore , the fact that the modulation seems to be periodic argues against the possibility that it is produced by any of such effects and implies that is associated with an intrinsic star variability . we computed the probability that the association between source 3 and its candidate grond counterpart is due to a chance coincidence . we computed the probability as @xmath57 , where @xmath58 is the matching radius used for source 3 ( 18 ) and @xmath59 is the density of stellar objects in the grond field , regardless of their brightness , measured in the co - addition of all g-band exposures . for a stellar density @xmath60 square degree@xmath7 we estimated a chance coincidence probability @xmath61 , which makes a chance coincidence unlikely . to confirm the existence of a periodic modulation of the source 3 candidate counterpart , we carried out a periodicity analysis based on the generalized lombe - scargle periodogram method ( lomb 1976 ; scargle 1982 ; zechmeister & kuerted 2009 ) . for cross - checking purpose , we also used the phase dispersion minimisation technique ( pdm ; stellingwerf 1978 ) using the pdm code in iraf and the period04 software package ( lenz & breger 2005 ) , which is especially dedicated to the statistical analysis of large astronomical time series containing gaps ( see figure [ grond - lc ] ) . all methods indicate the presence of a periodicity with a period of @xmath10 0.227 d. the analysis of the power spectrum of the optical time series shows a clear peak at the corresponding frequency , with a probability that is due to a chance noise fluctuation ( false - alarm probability ) of @xmath10 1.8@xmath6210@xmath63 ( @xmath10 8@xmath41 ) . the best period was found at 0.22748@xmath20.00043 d in the optical bands and at 0.22799@xmath20.00062 d in the near - ir bands , where we estimated the period uncertainty following gilliland et al . the optical and near - ir best - fit periods of the source 3 candidate counterpart are consistent within the uncertainties , which provides further evidence that the observed modulation is real . the period of the optical / ir modulations seen in the grond data for the source 3 candidate counterpart is consistent with that seen in the _ xmm - newton _ data for source 3 ( 0.2245@xmath20.0081 d ; sect . [ x_var ] ) . therefore , the detection of virtually the same periodicity clearly indicates that the two objects are associated . therefore , based upon the x - ray and optical variability at the same period and the relatively low chance coincidence probability , we regard the association between source 3 and its grond candidate counterpart as robust . furthermore , since we based the selection of candidate x - ray counterparts to 3fgl j2039.6@xmath15618 on the search for variable sources , the optical / x - ray periodicity of source 3 makes it a very promising candidate . another possible candidate x - ray counterpart to 3fgl j2039.6@xmath15618 would be source 11 , the second brightest x - ray source detected in the 3fgl error circle , and the only other x - ray source with an obvious non - thermal spectrum ( table 1 ) . however , source 11 is not variable in x rays and is not associated with a periodic optical / near - ir grond counterpart . therefore , although it can not be firmly ruled out as a candidate x - ray counterpart to 3fgl j2039.6@xmath15618 , as of now , it is a by far a less likely candidate than source 3 . the same is true for all the other fainter x - ray sources in table 1 , whose poorly characterised x - ray spectra and sparse optical , near - uv , and near - ir flux measurements hamper a detailed multi - wavelength analysis of their properties and a non - ambiguous classification . the optical / near - ir light curves of the source 3 counterpart folded at the corresponding best - fit periods are shown in figure [ grond - lc ] ( right ) . a double - peak light curve is clearly visible , with a main peak and a secondary peak , separated in phase by @xmath64 . per each band , we determined the phase of the two peaks by fitting a gaussian function to their profiles to precisely compute their phase separations and errors . the peak phase separation remains constant in the optical ( @xmath65 ; g ) , while it seems to slightly increase in the near - ir ( @xmath66 ; j ) . to better recognise the light curve evolution , we defined four regions : the main peak ( @xmath67=0.20.5 ) , the secondary peak ( @xmath67=0.70.9 ) , the `` bridge '' ( @xmath67=0.50.7 ) , and the `` off - peak '' ( @xmath67=0.00.2 and @xmath67=0.91.0 ) . the shape of the light curve is similar in all bands , but the profile of the modulation changes from the optical to the near - ir ( figure [ grond - lc - diff ] , left ) . in particular , the primary peak becomes broader and its amplitude decreases , from @xmath10 0.4 magnitudes in the g@xmath19 band to @xmath10 0.2 magnitudes in the h band , and the difference between the primary and the secondary peaks decrease from 0.133 magnitudes in the g band to @xmath68 in the h band . similarly , the amplitude of the `` bridge '' decreases , becoming comparable to that of the `` off - peak '' region . there is also a possible evidence of a colour variation as a function of phase ( figure [ grond - lc - diff ] , right ) , which might indicate that we are observing regions of the star surface at different temperatures . in particular , the colours seem to be bluer in coincidence with the two peaks , and bluer in coincidence with the primary peak than with secondary one . the colours also seem bluer in the `` bridge '' than in the `` off - peak '' region . the colour variation seems less marked at longer wavelengths consistently with the fact that the light curve variations are smoother . unfortunately , the errors on the grond photometry calibration ( sectn . [ opt_uv ] ) make difficult to quantify the observed colour variations . we tried to align in phase the x - ray and optical light curves of source 3 to check the relative alignments between the x - ray and optical peaks . however , the difference between the epochs of the _ xmm - newton _ and grond observations ( mjd=5688556887 and mjd=56575 , respectively ) corresponds to a maximum time difference of 312 d. the accuracy on the best - fit optical period derived from the grond observations is 0.00043 d ( sectn . [ opt_var ] ) , which corresponds to a phase uncertainty of @xmath69 . thus , building a phase - coherent solution for the optical light curve backward to the epoch of the _ xmm - newton _ observation would bring an uncertainty of @xmath10 0.59 on the absolute phase determination , which is larger than the phase separation between the two peaks ( @xmath70 in the x rays and @xmath71 in the optical ) . we computed the time - average multi - band photometry of the source 3 counterpart from the grond data and obtained g@xmath19=19.40@xmath20.02 , r@xmath19=18.71@xmath20.02 , i@xmath19=18.59@xmath20.02 , z@xmath19=18.52@xmath20.02 , j=18.13@xmath20.03 , h=18.33@xmath20.03 , k=18.35@xmath20.06 , with all magnitudes in the ab system . the photometry errors account for both statistical errors and for the systematic uncertainty on the photometry calibration . we also identified the source 3 counterpart in the u and uvw1-filter exposures from the _ xmm - newton_/om with ab magnitudes u=21.26@xmath20.26 and m@xmath72=21.88@xmath20.4 ( table 2 ) , whereas it is not detected in the uvm2 filter down to a 3 @xmath41 limiting magnitude of 21.99 and in the _ swift_/uvot uvw2 image down to a limiting magnitude of 23.34 ( ab ) . in the near - ir , we also identified the source 3 counterpart in the vista images , with ab magnitudes j=18.24@xmath20.03 , h=18.24@xmath20.04 , and k@xmath22=18.64@xmath20.09 , converted from the native vega survey system . we found that the vista magnitudes ( epoch 2010.6 ) are all compatible with the grond ones ( epoch 2014.7 ) , after accounting for the difference between the k and k@xmath22 filters , which excludes long - term variability on year time scales from the source 3 counterpart . we used the time - averaged g@xmath19 , r@xmath19 , i@xmath19 , z@xmath19-band magnitudes of the source 3 counterpart as a reference for its classification by analysing its location in the observed ( i.e. not corrected for the reddening ) colour - magnitude ( cm ) and colour - colour ( cc ) diagrams of the field . the diagrams are shown in figure [ grond - cmd ] , where the location of the field stars is shown by the black filled circles and that of the source 3 counterpart as a red filled triangle . red and green triangles correspond to the location computed from the single - image photometry . in order to reject outliers and include only high - confidence measurements , we plotted only field stars for which at least 20 measurements per filter were available and with @xmath73 . we compared the observed cm and cc diagrams with simulated stellar sequences computed from the besanon models ( robin et al . 2004 ) for different stellar populations and distance values up to 15 kpc . the simulated sequences are shown in figure [ grond - cmd ] as the grey scale map . the dark grey regions in the cm diagrams correspond to a likely distance range ( @xmath74 pc ) for source 3 , whereas in the cc diagram the dark grey region corresponds to simulated magnitudes that are within @xmath2 0.05 the g@xmath19-band magnitude of the source 3 counterpart . the distance to source 3 is unknown a priori . the upper limit on the hydrogen column density derived from the fits to the x - ray spectrum of source 3 ( @xmath75 cm @xmath76 ; table [ tab1 ] ) indicates a distance lower than @xmath77 kpc , assuming the relation between distance and @xmath33 of he , ng & kaspi ( 2013 ) . without a parallax measurement , the distance to source 3 can not be precisely constrained from kinematic measurements of its optical counterpart . the nomad catalogue ( zacharias et al . 2005 ) gives a proper motion of @xmath78 mas yr@xmath7 and @xmath79 mas yr@xmath7 in right ascension and declination , respectively . this corresponds to a spatial velocity of @xmath80 @xmath62 ( d/1 kpc ) km s@xmath7 . if we equate it to the median of the transverse velocity distribution of msps ( @xmath10108 km s@xmath7 , with a standard deviation of @xmath1086 km s@xmath7 ) computed from the australia national telescope facility ( atnf ) pulsar catalogue ( manchester et al . 2005 ) we obtain a distance of @xmath107701500 pc , compatible with the estimate inferred from the @xmath33 . any determination of a lower limit on the distance is more uncertain . again , if source 3 were a binary msp , the distance distribution of known binary msps from the atnf pulsar catalogue gives a probability of @xmath10 0.006 to find one within a radius of 0.2 kpc . thus , the assumed distance range for source 3 ( @xmath74 pc ) is reasonable . we also used the upper limit on the @xmath33 to infer an interstellar extinction along the line of sight @xmath81 , after applying the relation of predehl & schmitt ( 1995 ) . then , we computed the extinction in the different filters using the extinction coefficients of fitzpatrick ( 1999 ) . the reddening vectors are shown in in figure [ grond - cmd ] for the limit case @xmath82 . since the field stars are affected by an unknown interstellar extinction , and the simulations based on the besanon models simply compute a reddening scaled proportionally to the assumed distance in a given direction , introducing a reddening correction in our simulations might bias a direct comparison between the observed and the simulated stellar sequences . therefore , for simplicity , in all cases we simulated the stellar sequences assuming a null reddening . then , we used the reddening vectors as a reference to trace the extinction - corrected locations of the observed points for the source 3 counterpart ( red points ) along the simulated stellar sequences . as seen , the location of the source 3 counterpart in the diagrams falls between the regions of the simulated ms and wd stellar sequences . only for distances as low as @xmath10 0.1 kpc the counterpart location in the diagrams could be compatible with a wd . however , if source 3 is an msp such possibility is unlikely ( see above ) . thus , we conclude that the star is , most likely , not a wd . we built the optical / near - uv / near - ir spectrum of the source 3 counterpart using the available multi - band photometry ( sect . [ cm ] ) . in all cases , we used as a reference the measured ab magnitudes to compute the spectral fluxes at the filter peak wavelengths . as a reference for the interstellar extinction correction we used a maximum extinction value of @xmath82 , derived from the upper limit on the hydrogen column density @xmath33 ( predehl & schmitt 1995 ) obtained with the fit with a pl spectral model ( sect . [ spectra ] ) . we fitted the spectrum with both a single and a double bb spectral model . however , we found that the optical / near - uv / near - ir data can not be simultaneously fitted by a single bb and that a double bb is required to fit the entire spectrum ( @xmath83 , 6 d.o.f . ) . the inferred temperatures are @xmath84 k for the hotter bb , which fits the optical / uv fluxes , and @xmath85 k , for the colder one , which fits the near - ir part of the spectrum . the two bb model is also consistent with the upper limits obtained in the om / uvw2 and uvot / uvm2 filters . the overall spectral shape and spectral parameters do not change significantly when adding the correction for the maximum estimated interstellar extinction ( @xmath86 k , @xmath85 k ) . while the temperature of the hot bb is compatible with the surface temperature of a mid - ms companion star , the temperature of the colder one is too low to be entirely ascribed to the emission from the star surface . although this can contribute to part of the observed near - ir emission , as indicated by the periodic modulation of the j , h and k - band light curves , an additional source external to the star is required to account for the low temperature of the bb that fits the near - ir part of the spectrum . this source might be associated with emission from cold intrabinary gas or dust , maybe the residual of an accretion disk left over by a past phase of matter accretion on the neutron star . the analysis of the counterpart colours as a function of phase ( figure [ grond - lc - diff ] , right ) suggests that its spectrum slightly changes along the @xmath10 0.2245 d period . to quantify this possible evolution we fitted the multi - band spectrum in the four phase intervals defined in sect . [ opt_lc_src3 ] . like in our phase - resolved colour analysis , we can not use the single - epoch flux measurements in the u and uvw1 bands obtained with the _ xmm - newton_/om . as done above , we fitted the four phase - resolved spectra using a two - bb model , considering both null and maximum interstellar extinction . however , we did not find evidence of a significant spectrum evolution across the different phase intervals . this is partially ascribed to the fact the spectra are less constrained at shorter wavelengths without the flux measurements in the u and uvw1 bands .

we present multi - wavelength observations of the unassociated-ray source 3fgl j2039.6 detected by the _ fermi _ large area telescope . the source-ray properties suggest that it is a pulsar , most likely a millisecond pulsar , for which neither radio nor-ray pulsations have been detected yet . the brightest of these x - ray sources is variable with a period of 0.2245.0081 d. its x - ray spectrum can be described by a power law with photon index , and hydrogen column density , which gives an unabsorbed 0.310 kev x - ray flux of erg s . the light curve profile of the companion star , with two asymmetric peaks , suggests that the optical emission comes from two regions at different temperatures on its tidally - distorted surface . based upon its x - ray and optical properties , we consider this source as the most likely x - ray counterpart to 3fgl j2039.6 , which we propose to be a new redback system .

we present multi - wavelength observations of the unassociated-ray source 3fgl j2039.6 detected by the _ fermi _ large area telescope . the source-ray properties suggest that it is a pulsar , most likely a millisecond pulsar , for which neither radio nor-ray pulsations have been detected yet . we observed 3fgl j2039.6 with _ xmm - newton _ and discovered several candidate x - ray counterparts within / close to the-ray error box . the brightest of these x - ray sources is variable with a period of 0.2245.0081 d. its x - ray spectrum can be described by a power law with photon index , and hydrogen column density , which gives an unabsorbed 0.310 kev x - ray flux of erg s . observations with the gamma - ray burst optical / near - infrared detector ( grond ) discovered an optical counterpart to this x - ray source , with a time - averaged magnitude . the counterpart features a flux modulation with a period of 0.22748.00043 d that coincides , within the errors , with that of the x - ray source , confirming the association based on the positional coincidence . we interpret the observed x - ray / optical periodicity as the orbital period of a close binary system where one of the two members is a neutron star . the light curve profile of the companion star , with two asymmetric peaks , suggests that the optical emission comes from two regions at different temperatures on its tidally - distorted surface . based upon its x - ray and optical properties , we consider this source as the most likely x - ray counterpart to 3fgl j2039.6 , which we propose to be a new redback system .

1509.07474

c

we carried out multi - wavelength observations of the unidentified _ fermi_-lat source 3fgl j2039.6@xmath15618 with _ xmm - newton _ and grond . we detected a likely x - ray counterpart ( source 3 ) within the @xmath0-ray error box of 3fgl j2039.6@xmath15618 , which is characterised by a pl x - ray spectrum ( @xmath3 ) that is indicative of strong magnetospheric emission . the upper limit on the hydrogen column density inferred from the x - ray spectral fit , @xmath4 @xmath5 , imply a distance probably lower than 1 kpc . the x - ray light curve of source 3 features a modulation with a period of 0.2245@xmath20.0081 d and two peaks , separated in phase by @xmath70 . using the grond data , we found an optical counterpart to source 3 that features an asymmetric , double - peaked , light curve and a flux modulation with a period of 0.22748@xmath20.00043 d , coincident with that measured in the x rays . if we interpret this periodicity as the orbital period of a compact binary system , source 3 would probably be a binary msp and , as such , a very likely counterpart to 3fgl j2039.6@xmath15618 . in particular , both the optical colors of its putative companion star and the optical light curve profile , with two asymmetric peaks separated in phase by @xmath64 , suggest that source 3/3fgl j2039.6@xmath15618 is a rb . this hypothesis is supported by the lack of apparent radio emission , which would be explained by eclipse of the radio signal as it propagates through the evaporated atmosphere of the irradiated msp companion , as observed in many rbs . optical spectroscopy observations of source 3 will be essential to obtain a more accurate classification of its companion star and measure its radial velocity curve , crucial to confirm the binary msp scenario and determine the orbital parameters of the binary system . a precise determination of the orbital parameters is necessary to fold @xmath0-ray photons and search for the msp pulsations . a timing solution , that can be extended back in time to the launch of _ fermi _ in 2008 , will provide even tighter constraints on the orbital parameters and their evolution . this has a potentiially huge scientific payoff in terms of fundamental physics ( romani et al . , 2012 ; pletsch & clark , 2015 ) the research leading to these results has received funding from the european commission seventh framework programme ( fp7/2007 - 2013 ) under grant agreement n. 267251 . this work was supported by the asi - inaf contract i/004/11/0 , art.22 l.240/2010 for the project `` studio di sorgenti di alta energia con swift '' . cd acknowledges support through extras , funded from the european union s seventh framework programme for research , technological development and demonstration under grant agreement no 607452 . part of the funding for grond ( both hardware as well as personnel ) was generously granted from the leibniz - prize to prof . g. hasinger ( dfg grant ha 1850/28 - 1 ) . cccccccc & j2000 coord . & counts rate & spectral & n@xmath115 & @xmath116 & flux@xmath117}$ ] & variability + & ra dec [ @xmath118 ( stat . & @xmath49 cts / s & model & @xmath119 @xmath5 & & @xmath120erg @xmath5 s@xmath7 & @xmath39 ( d.o.f . ) + 3 & 309.8956 -56.2861 ( 0.3 ) & 23.78@xmath20.99 & pl & @xmath121 & 1.36@xmath20.09 & 10.19@xmath122 & 66.18 ( 16 ) + 11 & 309.8439 -56.3292 ( 0.6 ) & 10.76@xmath20.79 & pl & @xmath123 & 1.33@xmath124 & 5.73@xmath125 & 3.92 ( 8) + 13 & 309.9995 -56.3359 ( 0.5 ) & 4.90@xmath20.57 & pl / ap & @xmath126 & 2.07@xmath127 & 2.66@xmath128 & 4.0 ( 8) + 19 & 309.8170 -56.2838 ( 0.9 ) & 6.51@xmath20.72 & pl / ap & @xmath129 & 1.54@xmath130 & 2.98@xmath131 & 3.8 ( 8) + 22 & 309.8713 -56.3320 ( 0.7 ) & 7.84@xmath21.36 & pl / ap & @xmath132 & 1.80@xmath133 & 3.37@xmath134 & 11.9 ( 8) + 24 & 309.9619 -56.2989 ( 0.8 ) & 4.44@xmath20.46 & pl / ap & @xmath135 & 1.86@xmath136 & 1.24@xmath137 & 4.1 ( 8) + 29 & 309.8415 -56.3154 ( 1.0 ) & 5.19@xmath20.71 & pl / ap / bb & @xmath138 & 2.37@xmath139 & 1.36@xmath140 & 6.2 ( 8) + 31 & 309.8172 -56.2948 ( 0.8 ) & 4.21@xmath20.54 & pl / ap / bb & @xmath141 & 1.80@xmath142 & 3.31@xmath143 & 7.4 ( 8) + 40 & 309.9936 -56.3097 ( 1.1 ) & 3.03@xmath20.50 & pl / ap & 0.05 & 2 & 0.63@xmath144 & 6.25 ( 6 ) + 44 & 309.8651 -56.2619 ( 1.5 ) & 2.46@xmath20.44 & pl / ap / bb & 0.05 & 2 & 0.11@xmath145 & 5.5 ( 5 ) + 52 & 309.9451 -56.3099 ( 1.3 ) & 2.00@xmath20.35 & pl / bb & @xmath146 & 1.11@xmath147 & 1.67@xmath148 & 2.6 ( 5 ) + 60 & 309.9159 -56.3583 ( 1.4 ) & 1.78@xmath20.32 & pl / ap / bb & @xmath149 & 2.33@xmath150 & 0.49@xmath151 & 4.4 ( 4 ) + 72 & 309.8419 -56.3541 ( 1.6 ) & 1.58@xmath20.41 & pl / ap / bb & 0.05 & 2 & 0.74@xmath152 & 0.7 ( 3 ) + 76 & 309.9548 -56.3170 ( 2.0 ) & 1.10@xmath20.29 & pl / ap / bb & 0.05 & 2 & 0.68@xmath153 & 1.0 ( 3 ) + 85 & 309.8740 -56.3390 ( 1.6 ) & 1.24@xmath20.43 & pl / ap & 0.05 & 2 & 0.74@xmath154 & 0.64 ( 3 ) + 88 & 309.9357 -56.2766 ( 1.7 ) & 1.62@xmath20.43 & & & & & 8.89 ( 3 ) + c|ccccccc|ccc|ccc|cccccc i d & & & & + & g & r & i & z & j & h & k & j & h & k@xmath22 & u & uvw1 & uvm2 & uvw2 + 3 & 19.40 & 18.73 & 18.72 & 18.61 & 18.53 & 18.15 & 18.34 & 18.24 & 18.24 & 18.64 & & 21.26 & & 21.88 + 11 & & & & & & & & 20.33 & 20.02 & 20.73 & & & & + 13 & & & 22.61 & & & & & & & 20.70 & & 21.27 & & + 19 & & & & & & & & & & 20.64 & & & & + 22 & & & & & 19.37 & & 17.88 & & & & & & & + & & & & & 18.02 & 17.96 & & 17.84 & 17.93 & 17.97 & & & & + 24 & 24.21 & & & & & & & & & & & & & + 29 & & & & & & & & & & & 20.83 & 20.39 & & + 40 & 21.95&21.22 & 21.45 & 22.92 & & & & & 19.82 & 19.85 & 20.10 & 22.08 & & & + 72 & & & & & & & & & 19.66 & & & & & + 60 & & & & & & & & & & & & 19.33 & & & + 76 & 19.64 & 18.36 & 18.63 & 18.20 & 17.65&17.66&17.77 & 17.63 & 17.58 & 17.90 & & & & + & & & & 21.52 & & & & 19.36 & 18.84 & 18.64 & & & & + & & & & 23.97 & & & & & & & & & & + 88 & & & & & & & & 20.93 & 21.31 & & & & & + ) . the vertical dashed lines define the main peak ( @xmath67=0.20.5 ) , the secondary peak ( @xmath67=0.70.9 ) , the `` bridge '' ( @xmath67=0.50.7 ) , and the `` off - peak '' ( @xmath67=0.00.2 and @xmath67=0.91.0 ) regions . [ grond - lc],width=529 ] 5618 field obtained from the grond time - averaged photometry . _ bottom _ : observed cc diagram . in all panels , the location of field stars is indicated by the black filled circles , whereas that of the optical counterpart of the _ xmm - newton _ source 3 is indicated by the red filled triangle . the filled green triangles indicates the counterpart location computed from the photometry computed on the single image . stellar sequences simulated from the besanon models for different values of distance are shown in light and dark grey . in the cm diagrams the dark grey regions correspond to distance values @xmath155 pc , whereas in the cc diagram they correspond to magnitudes within @xmath2 0.05 the g-band magnitude of the source 3 counterpart . the ms and wd branches are labelled . [ grond - cmd],title="fig:",width=340 ] 5618 field obtained from the grond time - averaged photometry . _ bottom _ : observed cc diagram . in all panels , the location of field stars is indicated by the black filled circles , whereas that of the optical counterpart of the _ xmm - newton _ source 3 is indicated by the red filled triangle . the filled green triangles indicates the counterpart location computed from the photometry computed on the single image . stellar sequences simulated from the besanon models for different values of distance are shown in light and dark grey . in the cm diagrams the dark grey regions correspond to distance values @xmath155 pc , whereas in the cc diagram they correspond to magnitudes within @xmath2 0.05 the g-band magnitude of the source 3 counterpart . the ms and wd branches are labelled . [ grond - cmd],title="fig:",width=340 ] 5618 field obtained from the grond time - averaged photometry . _ bottom _ : observed cc diagram . in all panels , the location of field stars is indicated by the black filled circles , whereas that of the optical counterpart of the _ xmm - newton _ source 3 is indicated by the red filled triangle . the filled green triangles indicates the counterpart location computed from the photometry computed on the single image . stellar sequences simulated from the besanon models for different values of distance are shown in light and dark grey . in the cm diagrams the dark grey regions correspond to distance values @xmath155 pc , whereas in the cc diagram they correspond to magnitudes within @xmath2 0.05 the g-band magnitude of the source 3 counterpart . the ms and wd branches are labelled . [ grond - cmd],title="fig:",width=340 ] , r@xmath19 , i@xmath19 and z@xmath19 bands are marked by green , red , magenta and cyan circles . only statistical errors are plotted . the black lines display the best - fit light curve calculated using the model described in sec . [ opt_model ] . [ grond - lc - model],width=453 ]

the counterpart features a flux modulation with a period of 0.22748.00043 d that coincides , within the errors , with that of the x - ray source , confirming the association based on the positional coincidence . we interpret the observed x - ray / optical periodicity as the orbital period of a close binary system where one of the two members is a neutron star .

we present multi - wavelength observations of the unassociated-ray source 3fgl j2039.6 detected by the _ fermi _ large area telescope . the source-ray properties suggest that it is a pulsar , most likely a millisecond pulsar , for which neither radio nor-ray pulsations have been detected yet . we observed 3fgl j2039.6 with _ xmm - newton _ and discovered several candidate x - ray counterparts within / close to the-ray error box . the brightest of these x - ray sources is variable with a period of 0.2245.0081 d. its x - ray spectrum can be described by a power law with photon index , and hydrogen column density , which gives an unabsorbed 0.310 kev x - ray flux of erg s . observations with the gamma - ray burst optical / near - infrared detector ( grond ) discovered an optical counterpart to this x - ray source , with a time - averaged magnitude . the counterpart features a flux modulation with a period of 0.22748.00043 d that coincides , within the errors , with that of the x - ray source , confirming the association based on the positional coincidence . we interpret the observed x - ray / optical periodicity as the orbital period of a close binary system where one of the two members is a neutron star . the light curve profile of the companion star , with two asymmetric peaks , suggests that the optical emission comes from two regions at different temperatures on its tidally - distorted surface . based upon its x - ray and optical properties , we consider this source as the most likely x - ray counterpart to 3fgl j2039.6 , which we propose to be a new redback system .

1605.00742

c

as a function of eddington ratio for our _ chandra _ targets ( red filled star symbols ) , the four mbh agn with @xmath187 from ( * ? ? ? * blue triangles ) , the two mbh agn with @xmath187 from ( * ? ? ? * cyan upside down triangles ) , and the high-@xmath4 sample ( circles ) . arrows denote upper limits on @xmath3 . the open star symbols represent our two less confident agn candidates ( galaxies 7 and 82 ; see section [ sec : optical ] ) . ] here , we compare the x - ray properties of the lower - eddington ratio agn to the high-@xmath4 sample ( differences between the x - ray properties of accreting mbhs vs. smbhs have already been explored in depth by ; also see @xcite ) . we generally exclude the two lower - confidence agn candidates ( galaxies 7 and 82 ) from the following discussion , unless stated otherwise . our low-@xmath4 sample therefore contains 11 objects , and the high-@xmath4 comparison samples contains 67 objects . as noted in section [ sec : lbol ] , we adopt the @xmath4 estimates from , as that provides the most straightfoward method for uniformly comparing @xmath4 across the entire 78 object sample . while these estimates may be systematically offset from the `` true '' @xmath4 values , the estimates provide a reliable tracer for the _ relative _ eddington ratios between objects in the full sample . we can not calculate @xmath4 from @xmath181 [ ] across the entire sample because not all objects show narrow - line agn signatures . the full 78 object sample shows a large dispersion in @xmath3 ( see section [ sec : wlq ] ) , which implies that applying an x - ray based bolometric correction for determining @xmath4 is not straightforward , and would likely require an undetermined correction that is dependent on @xmath3 . report on the lack of a correlation between @xmath3 and @xmath116 within just the high-@xmath4 sample ( also see @xcite ) . after extending the dynamic range in @xmath116 by almost an order of a magnitude , we do not see any correlation either ( figure [ fig : aox ] ) . we perform a linear regression on @xmath3 vs. @xmath116 ( including upper limits on @xmath3 ; @xcite ) , and we find a slope consistent with zero ( @xmath188 ) . furthermore , generalized kendall s @xmath189 and spearman s @xmath190 correlation tests on the combined 78 object sample both indicate that no correlation is present at the @xmath191 level . we incorporate upper limits on the x - ray non - detections when running these correlation tests by using the astronomy survival analysis ( asurv ) package rev 1.2 @xcite , which implements the statistical methods presented in @xcite . the lack of a correlation within just the 67 object high-@xmath4 sample reported by is therefore not solely due to their limited dynamic range . in addition , we do not see any evidence for statistically different x - ray properties between the low- and high-@xmath4 samples . a peto - prentice test ( run through asurv to incorporate upper limits ) indicates that the low- and high - eddington ratio samples do not follow statistically different distributions in @xmath3 ( @xmath192 ; also see figures [ fig : xray]d and [ fig : aox ] ) . we also estimate the average @xmath3 values for each distribution using the kaplan - meier estimator in asurv . the 11 lower-@xmath4 agn have a mean @xmath193 , which is comparable to @xmath194 for the 67 object high-@xmath4 sample . furthermore , for our four _ chandra _ objects to which we could fit a spectrum , we similarly do not see any meaningful differences in the spectral properties between the two samples ( figure [ fig : xray]c ) . we might have expected to see a correlation between ( hard x - ray ) @xmath81 and @xmath116 , as is observed for luminous quasars with @xmath195 ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) , but proper investigation will require a sample with tighter x - ray spectral constraints , and thus deeper x - ray observations . as a function of @xmath153 for our low-@xmath4 _ chandra _ targets ( red star symbols ; excluding the less - confident agn in galaxies 7 and 82 ) , the four @xcite low-@xmath4 objects ( blue triangles ) , the two @xcite low-@xmath4 objects ( cyan upside down triangles ) , and the 67 objects from the high-@xmath4 mbh sample ( circles ) . for comparison , we plot samples of more massive black holes , including wlqs ( at @xmath196 ; orange diamonds ) , `` normal '' type 1 sdss quasars from ( * * squares ) , and the best - fit @xmath197 relation from ( * ? ? ? * solid line ) . all open symbols denote upper limits on @xmath3 . ] the lower-@xmath4 mbhs appear to show as wide of a spread in @xmath3 as the high-@xmath4 sample ( see figure [ fig : aox ] ) . given that very few mbhs display signs of x - ray absorption ( and those that do typically have moderate column densities , @xmath198 @xmath86 ) , some mbhs might be intrinsically x - ray weak . they could be similar to the nearby ( z=0.192 ) narrow - line seyfert 1 galaxy phl 1811 , which may have a smaller or quenched x - ray corona ( e.g. , * ? ? ? * ; * ? ? ? intriguingly , the range in @xmath3 displayed by mbhs is also reminiscent of the x - ray properties of weak emission line quasars ( wlqs ; see , e.g. , @xcite ) . wlqs are higher - redshift ( mostly known at @xmath199 ) , unobscured , radio - quiet quasars that have unusually weak high - ionization broad emission lines ( especially ly@xmath22 and @xmath2001549 ; see , e.g. , @xcite ) . approximately 50% of known wlqs are significantly x - ray weaker than expected for their uv luminosities ( with @xmath201 ; see @xcite ) . in figure [ fig : aoxwlq ] , we compare the @xmath3 distribution of mbhs to wlqs as a function of @xmath153 , with typical sdss type 1 quasars from @xcite plotted for reference . we include 38 wlqs that were optically - selected from the sdss , that have @xmath196 ( to ensure sdss spectroscopic coverage of the high - ionization emission line ) , and that have _ chandra _ x - ray observations presented by @xcite and @xcite . were initially selected as high - redshift analogs to phl 1811 , which are nearly always x - ray weak and appear to share many similarities to wlqs in their optical and uv spectra . for convenience , we refer to all objects studied by @xcite and @xcite as wlqs . ] the lack of wlqs at @xmath202 hz@xmath31 in figure [ fig : aoxwlq ] is largely ( but unlikely solely ) due to the restriction in redshift . it is clear from figure [ fig : aoxwlq ] that both the mbh and wlq populations display a larger dispersion in @xmath3 compared to ` normal ' type 1 sdss quasars . to quantify the dispersion , we use the kaplan - meier estimator . since we do not see any statistical difference in the x - ray properties between the low- and high-@xmath4 mbh samples , we consider the entire 78 object mbh sample in the following , in order to improve statistics . we find that the @xmath203 - 75@xmath204 percentiles of the @xmath3 distributions for the 78 mbhs and 38 wlqs span a range of @xmath205 and @xmath206 , respectively ( errors are the standard deviations on the @xmath203 and 75@xmath204 percentile @xmath3 values added in quadrature ) ; when limiting the comparison @xcite sdss quasars to similar luminosities as the wlq sample ( 120 type 1 quasars with @xmath207 hz@xmath31 ) , luminous quasars have 25@xmath204 - 75@xmath204 percentiles spanning only @xmath208 in @xmath3 . the larger dispersion hints at a potential difference in accretion properties between mbh agn and ` normal ' type 1 quasars . in the next subsection , we consider an analogy with wlqs to explore one potential mechanism for the larger dispersion in @xmath3 , namely accretion via a slim disk . for @xmath209 , accretion is expected to take place in the `` slim disk '' regime ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) , where advective cooling losses are comparable to radiative losses , and the accretion flow becomes geometrically thick and radiatively inefficient ( see , e.g. , section 6 of * ? ? ? * for a brief review ) . @xcite propose that the unusual x - ray properties of wlqs ( i.e. , the large fraction of x - ray weak objects ) may be related to accretion via slim disks , as described below . @xcite initially suggested that wlqs contain a column of x - ray shielding gas that is very local to the black hole ( interior to the broad emission line region ) ; this x - ray shielding gas can produce highly x - ray weak objects at certain orientations , and x - ray normal objects at other orientations . @xcite went on to physically associate this shielding gas with the inner edge of a ( geometrically thick ) slim disk . in this picture , all wlqs are fed by an inner slim disk , but only the ones oriented such that we are viewing the central engine through the `` puffed up '' disk material appear to be x - ray weak . for these x - ray weak objects , the direct x - ray continuum will be highly absorbed , and any detected x - ray emission should be dominated by reflected / scattered light @xcite . this scenario results in the population of wlqs as a whole displaying a large observed dispersion in @xmath3 . it is tempting to appeal to a similar scenario to explain the large dispersion in @xmath3 observed for mbhs . however , if such a scenario were to apply to mbh agn , then we expect to see a systematic change in the x - ray properties of the 78-object mbh sample around @xmath210 , as the accretion flow transitions between a geometrically thick slim disk and a geometrically thin ( radiatively efficient ) @xcite disk . in particular , we should see less dispersion in @xmath3 at @xmath211 , in the context of a scenario where x - rays at these lower eddington ratios originate from inverse compton scattering of disk uv photons off a hot corona that is energetically coupled to a thin disk ( e.g. , * ? ? ? * ) . for @xmath211 , the higher uv flux from the thin disk would increase the number of inverse compton scatterings , thereby cooling the corona and also producing mildly steeper x - ray spectra on average ( e.g. , * ? ? ? a systematic change in the x - ray properties , as described above , is not observed among the mbh sample . however , when comparing @xmath116 estimates from different methods in table [ tab : lledd ] , we can not exclude the possibility that the eddington ratios adopted for both the low- and high-@xmath4 mbh samples are systematically underestimated , by perhaps up to an order of magnitude . if so , then nearly all of the high-@xmath4 sample would be in the super - eddington regime , and several of the lower-@xmath4 objects would fall close to the proposed `` slim disk '' transition . furthermore , we could also be systematically underestimating @xmath4 for our _ chandra _ targets if their virial - based @xmath158 estimates happen to be too large . thus , we can not exclude the possibility that the entire mbh agn sample could feasibly be more rapidly accreting than they appear to be in figure [ fig : aox ] , in which case wlqs may provide useful insight into understanding accretion onto the mbh sample considered here . we note that limited information on eddington ratios for wlqs seems to point toward @xmath212 ; @xcite ) . our x - ray stacking analysis of the x - ray non - detected mbhs yields a relatively hard x - ray spectrum ( @xmath213 ) . for the objects with small @xmath3 , the inner edge of the slim disk modifies the `` intrinsic '' x - rays associated with the agn corona , and any observed x - rays are likely dominated by reflection / scattering , such that a hard x - ray spectrum is expected . among wlqs , an x - ray stacking analysis of the subpopulation of x - ray weak objects reveals a hard x - ray spectrum as well ( @xmath214 ; * ? ? ? * also see @xcite ) . the similarly hard ( average ) spectra of the subsets of x - ray weak mbh agn and x - ray weak wlqs may futher support a wlq analogy . of course , the error bars on @xmath81 for our stacked mbhs are large ( see table [ tab : xstack ] ) . still , we find this to be an intriguing result , motivating a need for tighter x - ray spectral constraints for a sample of mbh agn spanning both high- and low- @xmath3 , in order to rigorously compare @xmath81 as a function of @xmath3 . if the wlq analogy holds , then we require samples of mbhs that are accreting even more weakly than our low-@xmath4 sample , in order to search for a slim - to - thin disk transition by searching for systematic changes in the x - ray properties described earlier ( i.e. , less dispersion in @xmath3 and steeper @xmath81 at lower eddington ratios in the thin disk regime ) . the prototype mbh ngc 4395 @xcite has a well - determined bolometric luminosity @xmath215 from a highly sampled broadband spectrum @xcite , providing @xmath216 for @xmath217 @xcite . intriguingly , ngc 4395 is not only accreting below the expected slim - to - thin disk transition at 0.10.3 @xmath4 , but it is also near / below another critical accretion regime at @xmath80.01@xmath218 where the disk is expected to switch from a thin disk to a radiatively inefficient accretion flow ( riaf ) , ) and low - accretion rate riafs ( @xmath219 ) are both radiatively inefficient , the physical reasons for their radiative inefficiencies are quite different . slim disks are radiatively inefficient largely because of photon trapping effects at near - eddington luminosities ; in most low - accretion rate riaf models , the low radiative efficiency is mainly due to weak coulomb coupling in the accretion flow ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? for other variants of riafs at low - accretion rates , also see , e.g .. @xcite . ] as described below . for agn fed by a thin disk , the x - ray photon index @xmath81 is correlated with eddington ratio when @xmath220 ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? below @xmath80.01 @xmath218 , @xmath81 and @xmath4 are anti - correlated , so that agn show the hardest x - ray spectra around @xmath221 , which may indicate a transition from a thin disk to a riaf around 1% @xmath218 ( e.g. , @xcite ; note that @xmath81 eventually plateaus to @xmath222 at the lowest eddington ratios , e.g. , @xcite ) . this x - ray spectral behavior is observed for stellar mass black holes in x - ray binary systems as well ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) , suggesting that it is a universal feature of black hole accretion , regardless of black hole mass . ngc 4395 supports this trend for mbhs , as it displays a hard photon index @xmath223 at @xmath224 @xcite . we have no reason to suspect that the bolometric luminosity of ngc 4395 could be biased in the same manner as for the other mbhs ( since its @xmath174 is calculated from an observed broadband spectrum of the nucleus ) . the physical mechanism for the small @xmath81 for ngc 4395 is therefore different than the small @xmath81 discussed earlier in the context of a slim disk . this intriguing trend is of course far from robust being based on a single source , and it further motivates a need for high signal - to - noise x - ray spectra for mbhs across a wide range of @xmath4 . a sizeable population of lower-@xmath4 mbh agn is unlikely accessible from optical - selection techniques , however , and recovering such objects will require complementary multiwavelength searches . high - spatial resolution x - ray surveys ( especially when combined with the radio ) are a promising avenue for revealing weakly accreting black holes ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * also note galaxies 53 and 56 in the current work that show x - ray signatures of an agn , but lack optical photoionization signatures of activity . ) . success has also been achieved through infrared surveys ( e.g. , * ? ? ? * ) , as well as fast variability @xcite . we stress that it is unclear if the optically - based @xmath4 measurements are indeed systematically underestimated , and the above wlq analogy is only meant to represent one possibility . if the adopted @xmath4 estimates are accurate , then there does not appear to be a distinct eddington ratio that marks a transition in radiative efficiency . in that case , a range of accretion disk / corona properties may contribute to the dispersion in @xmath3 , which may include a substantial number of intrinsically x - ray weak agn . to confirm or refute current @xmath4 estimates , broadband spectral energy distributions for a substantially larger number of mbhs are required to properly constrain the bolometric corrections for this population . such a project will require high - resolution imaging across the entire electromagnetic spectrum to separate the agn from the host galaxy ( see for further discussion , as well as , e.g. , @xcite , for examples of well - sampled broadband spectra ) .

we compare the x - ray properties of these seven low - mass active galactic nuclei ( agn ) to a total of 73 other low - mass agn in the literature with published _ chandra _ observations ( with eddington ratios extending from ) . we do not find any statistical differences between low- and high - eddington ratio low - mass agn in the distributions of their x - ray to ultraviolet luminosity ratios ( ) , or in their x - ray spectral shapes . our results indicate that between , there is no systematic change in the structure of the accretion flow for active galaxies hosting black holes . chandra _ observations , and it is plausible that their eddington ratios could be underestimated by up to an order of magnitude . if so , then in analogy with weak emission line quasars , we suggest that accretion from a geometrically thick , radiatively inefficient ` slim disk ' could explain their diverse properties in . alternatively ,

we present new _ chandra _ x - ray observations of seven low - mass black holes ( ) accreting at low - bolometric eddington ratios between . we compare the x - ray properties of these seven low - mass active galactic nuclei ( agn ) to a total of 73 other low - mass agn in the literature with published _ chandra _ observations ( with eddington ratios extending from ) . we do not find any statistical differences between low- and high - eddington ratio low - mass agn in the distributions of their x - ray to ultraviolet luminosity ratios ( ) , or in their x - ray spectral shapes . furthermore , the distribution of low- agn displays an x - ray weak tail that is also observed within high- objects . our results indicate that between , there is no systematic change in the structure of the accretion flow for active galaxies hosting black holes . we examine the accuracy of current bolometric luminosity estimates for our low- objects with new _ chandra _ observations , and it is plausible that their eddington ratios could be underestimated by up to an order of magnitude . if so , then in analogy with weak emission line quasars , we suggest that accretion from a geometrically thick , radiatively inefficient ` slim disk ' could explain their diverse properties in . alternatively , if current eddington ratios are in fact correct ( or overestimated ) , then the x - ray weak tail would imply that there is diversity in disk / corona couplings among individual low - mass objects . finally , we conclude by noting that the distribution for low - mass black holes may have favorable consequences for the epoch of cosmic reionization being driven by agn .

astro-ph0509195

r

the snls officially started in june 2003 ( there was a presurvey ramp - up to full operations ) , and we began using gemini - n and s to observe sn candidates in august 2003 ( semester 2003b ) . we usually obtain the gemini data within a day or two of the observations and produce `` real - time '' reductions . after the full calibration data is released at the end of a run the data are rereduced . here we report on the final spectroscopic reductions through november 2004 . all of the spectra used in this study are available in the online version of the paper . table [ der - table ] lists properties derived from the observations of each candidate , such as type , redshift , and epoch relative to maximum light . table [ class - host - table ] shows the distribution of sn types with respect to host galaxy type . while it is not always possible to extract the host galaxy separately and examine its sed , galaxy lines are apparent because they are narrower than sn features . therefore we group galaxies into absorption - line galaxies and emission - line galaxies ( if a galaxy has any emission lines it is considered an emission - line galaxy ) . just as at low redshift , in our sample core - collapse sne are never seen in absorption - line ( early type ) galaxies . figure [ hist ] is a histogram of the number of candidates of each different type with redshift . for clarity we group index 0 and 1 sne together as `` not ia '' and index 4 and 5 sne together as `` ia . '' sne with weaker classifications ( index 3 ) are plotted separately as `` ia*. '' candidates that could not be identified ( index 2 ) , but whose redshifts could be determined , are also shown . it is apparent that we targeted the highest redshift observations at gemini the median redshift of sne ia / ia * is 0.81 . as the redshift increases the fraction of less secure identifications rises , because for faint sne it is hard to achieve a high signal - to - noise ratio in a reasonable integration time . furthermore , at the higher redshifts one must rely more on the rest - frame uv light to classify the sne , and template uv observations of all sn types are scarce . core collapse sne cluster at lower redshifts on the histogram because they are usually intrinsically fainter . for example , a candidate with a peak magnitude of @xmath31 could be an sn ia at @xmath32 or could be a type ii sn at a lower redshift . the technique of the sn photo - z is introduced in section [ photozintro ] and described in much greater detail in @xcite . here we report the result of its application on our sn ia confirmation rate . the snls implemented the sn photo - z and improved real - time photometry in march 2004 , although in two cases after this ( 04d1dr and 04d4 ft ) , candidates had to be observed spectroscopically before a photo - z could be obtained . when no photo - z information was available before selecting candidates for spectroscopy , 14/26 ( 54% ) of the candidates were confirmed as sne ia close to previosly published rates . however , when we did have an sn photo - z to guide the decision making , the ia confirmation rate jumped to 27/38 ( 71% ) . there will be always be some unidentified candidates for which it is difficult to estimate a type from spectroscopy these may still be sne ia , but are too buried in a host , or have a spectrum with too low s / n , to be identified . however , where the photo - z excels is in its power to reject candidates that are not sne ia . with no prior photo - z information , 7/26 ( 27% ) of candidates with gemini spectroscopy were found to be certainly not or probably not sne ia . after implementation of the technique , only 3/38 ( 8% ) of the observations were certainly not or probably not sne ia . another benefit of the sn photo - z is that it provides a prediction of the time of maximum light for an sn ia , allowing observations to be scheduled to within a few days of this date for maximum efficiency and minimal host galaxy contamination . figure [ hiepoch ] shows the distribution of the sne ia observed by gemini with respect to maximum light . ninety percent of sne ia were observed within 0.5 mag of maximum light , and over half of the sne ia were observed within 0.1 mag of maximum light . it is clear that the flexibility provided by queue observing plays a large role in optimizing the efficiency of the spectroscopic classification of targets in the snls . note that it is not always possible to schedule observations at maximum light because we require dark time to observe such faint targets , and gmos is not always on the telescope and available in queue mode . figure [ hiepoch ] also shows that the least solid classifications ( index 3 ) , labeled ia * , were usually observed after maximum light . sne before maximum were almost always classified with more certainty . this is partially because after maximum light , especially around + 7 to + 10 days after max , it is often difficult to distinguish between sne ia and sne ic . by this time certain distinguishing sn ia features , such as 4000 , may no longer be apparent , and the sn ia line velocities have decreased to the range more typical of those found in sne ic . the more uncertain classifications ( sne ia * ) often occur near maximum light , because the most difficult sne ( those at the highest redshift or with the most host galaxy contamination ) can only be observed near maximum light . before or after maximum light they are so faint that they would not be placed in the spectroscopic observing queue . an added benefit to obtaining early spectroscopy is that sne ia show the greatest diversity at early times @xcite , when the spectroscopy is probing the outer layers of supernova . figure [ hiepoch ] shows that one compromise would be to target observations at about one week before maximum light . at @xmath33d , a typical ia is only about 0.25 fainter than at peak , near enough to peak brightness to make the observations feasible . at the same time it would provide an opportunity to observe sne ia when they show the greatest diversity and also are the most distinct from sne ic . this window of opportunity is very narrow , however . at @xmath34d a typical sn ia is 0.75 mag fainter than at peak in the restframe b - band still too faint compared to its host galaxy , and by @xmath35d sn ia spectra have lost some of their diversity . figure [ imagpi ] shows the i magnitude at the time of spectroscopy versus the percentage increase in i brightness in a 6 pixel ( 1.12 ) diameter at the time of spectroscopy . the percentage increase is measured relative to the reference image , where there is no supernova light . the i magnitude and percentage increase were measured from cfht images , interpolated to the time of spectroscopy . typically candidates were sent to gemini only if they were in the magnitude range @xmath36 . ( there are some exceptions , especially in the d3 field , which can not be seen by the vlt . ) it is apparent from figure [ imagpi ] that when the sn signal is greater than that of the host galaxy , candidate identification is relatively easy when the percentage increase is greater than 100% the candidates were not identified only 7% ( 2/30 ) of the time . clearly , image quality ( iq ) plays a role in whether or not sne can be successfully identified in the presence of significant host galaxy light , as shown in figure [ iqpi ] . we plot the image quality at the time of spectroscopy ( determined from the gemini acquisition image ) against the percent increase ( determined from cfht images as described above ) . if the iq was better than 0.55@xmath37 , candidates were identified 88% of the time . in good seeing the sn light is more concentrated and can be extracted in a narrow aperture , even in the presence of host contamination . the @xmath2 matching of the sn spectrum against a host and sn spectral template library produces more identifications , more robust identifications , and greater coverage of parameter space than traditional methods ( unaided expert matching by eye ) . this method works optimally with spectra that are free from systematic deviations , and whose errors are well characterized . it works exceptionally well with gmos nod and shuffle data , where systematic effects associated with sky subtraction are almost completely removed . correcting the spectra for telluric features also helps , as does a carefully generated error spectrum . while both the spectra in this paper and in were classified by the same person ( dah ) , here the @xmath2 matching software is upgraded with more template supernova and galaxy spectra . were not able to identify any candidates with a percentage increase below 25% , but in this work we have successfully identified several candidates with percent increases between 15%25% . it is unclear if this is due to software improvements , observing conditions , differences in the spectrographs used , or a better selection of candidates . figure [ date ] also shows that the spectroscopic epoch determined by the fitting program matches well with the epoch determined from the lightcurve . unlike the spectral feature age technique @xcite , it is important to note that this program is not specifically tuned to determine the epoch of an sn ia , and it makes no assumptions that the input spectrum is a ia ( it is possible for it to determine the epoch of an sn ib / c for example , although this has not been extensively tested ) . we find the remarkable result that our spectroscopic fitting technique can determine the epoch to within 2.5 days , despite the low s / n and significant host contamination in this data set .

we achieve an improvement in the sn ia spectroscopic confirmation rate : at gemini 71% of candidates are now confirmed as sne ia , compared to 54% using the methods of previous surveys . this is despite the comparatively high redshift of this sample , where the median sn ia redshift is ( ) . these improvements were realized because we use the unprecedented color coverage and lightcurve sampling of the snls to predict whether a candidate is an sn ia and estimate its redshift , before obtaining a spectrum , using a new technique called the `` sn photo - z . '' in addition , we have improved techniques for galaxy subtraction and sn template fitting , allowing us to identify candidates even when they are only 15% as bright as the host galaxy . the largest impediment to sn identification

we present new techiques for improving the efficiency of supernova ( sn ) classification at high redshift using 64 candidates observed at gemini north and south during the first year of the supernova legacy survey ( snls ) . the snls is an ongoing five year project with the goal of measuring the equation of state of dark energy by discovering and following over 700 high - redshift sne ia using data from the canada - france - hawaii telescope legacy survey . we achieve an improvement in the sn ia spectroscopic confirmation rate : at gemini 71% of candidates are now confirmed as sne ia , compared to 54% using the methods of previous surveys . this is despite the comparatively high redshift of this sample , where the median sn ia redshift is ( ) . these improvements were realized because we use the unprecedented color coverage and lightcurve sampling of the snls to predict whether a candidate is an sn ia and estimate its redshift , before obtaining a spectrum , using a new technique called the `` sn photo - z . '' in addition , we have improved techniques for galaxy subtraction and sn template fitting , allowing us to identify candidates even when they are only 15% as bright as the host galaxy . the largest impediment to sn identification is found to be host galaxy contamination of the spectrum when the sn was at least as bright as the underlying host galaxy the target was identified more than 90% of the time . however , even sne on bright host galaxies can be easily identified in good seeing conditions . when the image quality was better than 0.55 , the candidate was identified 88% of the time . over the five - year course of the survey , using the selection techniques presented here we will be able to add more confirmed sne ia than would be possible using previous methods .

astro-ph0509195

c

we have demonstrated several techniques for improving the yield of spectroscopically identified sne ia at high redshift ( @xmath43 ) . the sn photo - z is shown to effectively screen out non - ia candidates before they are observed spectroscopically . when no photometric redshifts were available , 35% of candidates turned out to be probably or certainly not sne ia after spectroscopy ( ci 0 or 1 ) . with photo - z information , the non - ia `` contamination '' rate dropped to 8% . using the photo - z we show that we can schedule sn observations to within a few tenths of a magnitude of maximum light , and that the optimal phase for sn ia identifcation and diversity is @xmath33 days . after spectroscopy , we show that by @xmath2 fitting of template sne we can effectively subtract host light and determine the type of an sn when the sn is only 15% as bright as the host in some cases . for targets where the sn is at least as bright as the underlying host , or when the image quality is exceptional ( better than 0.55 ) , the candidate is identified more than 90% of the time . using @xmath2 fitting we can also obtain an independent measurement of the spectroscopic epoch that agrees well with the phase determined from the lightcurve . these techniques have been developed using the first year s observations of the highest redshift candidates of the snls at gemini north and south . of the candidates observed at gemini , 41/64 are certain or probable sne ia . this is roughly one - third of the spectroscopic follow - up program of the snls . the techniques outlined here will add @xmath3 more confirmed sne ia over the five - year project to discover , confirm , and follow @xmath44 sne ia to measure the equation of state of dark energy . the snls collaboration gratefully acknowledges the assistance of pierre martin and the cfht queued service observations team . jean - charles cuillandre and kanoa withington were also indispensable in making possible real - time data reduction at cfht . we also thank gemini queue observers and support staff , especially inger jrgensen , kathy roth , percy gomez , and marcel bergmann , for both taking the data presented in this paper and making observations available quickly . canadian collaboration members acknowledge support from nserc and ciar ; french collaboration members from cnrs / in2p3 , cnrs / insu and cea ; portuguese collaboration members acknowledge support from fct - fundao para a cincia e tecnologia . snls relies on observations with megacam , a joint project of cfht and cea / dapnia , at the canada - france - hawaii telescope ( cfht ) which is operated by the national research council ( nrc ) of canada , the institut national des science de lunivers of the centre national de la recherche scientifique ( cnrs ) of france , and the university of hawaii . this work is based in part on data products produced at the canadian astronomy data centre as part of the canada - france - hawaii telescope legacy survey , a collaborative project of the national research council of canada and the french centre national de la recherche scientifique . this work is also based on observations obtained at the gemini observatory , which is operated by the association of universities for research in astronomy , inc . , under a cooperative agreement with the nsf on behalf of the gemini partnership : the national science foundation ( united states ) , the particle physics and astronomy research council ( united kingdom ) , the national research council ( canada ) , conicyt ( chile ) , the australian research council ( australia ) , cnpq ( brazil ) and conicet ( argentina ) . this research used observations from gemini program numbers : gn-2004b - q-16 , gs-2004b - q-31 , gn-2004a - q-19 , gs-2004a - q-11 , gn-2003b - q-9 , and gs-2003b - q-8 . , a. l. , matheson , t. , filippenko , a. v. , leonard , d. c. , tonry , j. , riess , a. g. , challis , p. , clocchiatti , a. , garnavich , p. m. , hogan , c. j. , jha , s. , kirshner , r. p. , leibundgut , b. , phillips , m. m. , schmidt , b. p. , schommer , r. a. , smith , r. c. , soderberg , a. m. , spyromilio , j. , stubbs , c. , suntzeff , n. b. , & woudt , p. 2000 , , 544 , l111 , c. , howell , d. a. , folatelli , g. , garavini , g. , nobili , s. , aldering , g. , amanullah , r. , antilogus , p. , astier , p. , blanc , g. , burns , m. s. , conley , a. , deustua , s. e. , doi , m. , ellis , r. , fabbro , s. , fadeyev , v. , gibbons , r. , goldhaber , g. , goobar , a. , groom , d. e. , hook , i. , kashikawa , n. , kim , a. g. , knop , r. a. , lee , b. c. , mendez , j. , morokuma , t. , motohara , k. , nugent , p. e. , pain , r. , perlmutter , s. , prasad , v. , quimby , r. , raux , j. , regnault , n. , ruiz - lapuente , p. , sainton , g. , schaefer , b. e. , schahmaneche , k. , smith , e. , spadafora , a. l. , stanishev , v. , walton , n. a. , wang , l. , wood - vasey , w. m. , & yasuda ( the supernova cosmology project ) , n. 2005 , , 430 , 843 , t. , blondin , s. , foley , r. j. , chornock , r. , filippenko , a. v. , leibundgut , b. , smith , r. c. , sollerman , j. , spyromilio , j. , kirshner , r. p. , clocchiatti , a. , aguilera , c. , barris , b. , becker , a. c. , challis , p. , covarrubias , r. , garnavich , p. , hicken , m. , jha , s. , krisciunas , k. , li , w. , miceli , a. , miknaitis , g. , prieto , j. l. , rest , a. , riess , a. g. , salvo , m. e. , schmidt , b. p. , stubbs , c. w. , suntzeff , n. b. , & tonry , j. l. 2005 , , 129 , 2352 , s. , aldering , g. , goldhaber , g. , knop , r. a. , nugent , p. , castro , p. g. , deustua , s. , fabbro , s. , goobar , a. , groom , d. e. , hook , i. m. , kim , a. g. , kim , m. y. , lee , j. c. , nunes , n. j. , pain , r. , pennypacker , c. r. , quimby , r. , lidman , c. , ellis , r. s. , irwin , m. , mcmahon , r. g. , ruiz - lapuente , p. , walton , n. , schaefer , b. , boyle , b. j. , filippenko , a. v. , matheson , t. , fruchter , a. s. , panagia , n. , newberg , h. j. m. , couch , w. j. , & the supernova cosmology project . 1999 , , 517 , 565 , s. , pennypacker , c. r. , goldhaber , g. , goobar , a. , muller , r. a. , newberg , h. j. m. , desai , j. , kim , a. g. , kim , m. y. , small , i. a. , boyle , b. j. , crawford , c. s. , mcmahon , r. g. , bunclark , p. s. , carter , d. , irwin , m. j. , terlevich , r. j. , ellis , r. s. , glazebrook , k. , couch , w. j. , mould , j. r. , small , t. a. , & abraham , r. g. 1995 , , 440 , l41 , a. g. , filippenko , a. v. , challis , p. , clocchiatti , a. , diercks , a. , garnavich , p. m. , gilliland , r. l. , hogan , c. j. , jha , s. , kirshner , r. p. , leibundgut , b. , phillips , m. m. , reiss , d. , schmidt , b. p. , schommer , r. a. , smith , r. c. , spyromilio , j. , stubbs , c. , suntzeff , n. b. , & tonry , j. 1998 , , 116 , 1009 , a. g. , filippenko , a. v. , leonard , d. c. , schmidt , b. p. , suntzeff , n. , phillips , m. m. , schommer , r. , clocchiatti , a. , kirshner , r. p. , garnavich , p. , challis , p. , leibundgut , b. , spyromilio , j. , & smith , r. c. 1997 , , 114 , 722 , a. g. , strolger , l. , tonry , j. , tsvetanov , z. , casertano , s. , ferguson , h. c. , mobasher , b. , challis , p. , panagia , n. , filippenko , a. v. , li , w. , chornock , r. , kirshner , r. p. , leibundgut , b. , dickinson , m. , koekemoer , a. , grogin , n. a. , & giavalisco , m. 2004 , , 600 , l163 llllrclrrr 03d1as & 02:24:24.520 & -04:21:40.19 & 2003 - 09 - 27 & 6000 & n+s & 720 & 0.41 & 23.96 & 1475 + 03d1ax & 02:24:23.320 & -04:43:14.41 & 2003 - 09 - 29 & 2400 & c & 720 & 0.61 & 23.16 & 65 + 03d1bk & 02:26:27.410 & -04:32:11.99 & 2003 - 09 - 28 & 4800 & n+s & 720 & 0.47 & 23.95 & 83 + 03d1cj & 02:26:25.081 & -04:12:39.89 & 2003 - 10 - 26 & 5400 & n+s & 720 & 0.57 & 24.11 & 76 + 03d1 cm & 02:24:55.288 & -04:23:03.68 & 2003 - 10 - 27 & 5400 & n+s & 720 & 0.72 & 23.77 & 970 + 03d1co & 02:26:16.238 & -04:56:05.76 & 2003 - 11 - 01 & 7200 & n+s & 720 & 0.84 & 23.64 & 188 + 03d1ew & 02:24:14.088 & -04:39:56.98 & 2003 - 12 - 21 & 7200 & n+s & 720 & 0.71 & 23.76 & 1661 + 03d1fp & 02:26:03.073 & -04:08:02.02 & 2003 - 12 - 26 & 7200 & n+s & 720 & 0.55 & 23.86 & 30 + 03d1fq & 02:26:55.683 & -04:18:08.10 & 2003 - 12 - 24 & 5400 & n+s & 720 & 0.48 & 23.59 & 41 + 03d4cj & 22:16:06.660 & -17:42:16.72 & 2003 - 08 - 26 & 2700 & c & 680 & 0.83 & 21.85 & 10000 + 03d4ck & 22:15:08.910 & -17:56:02.17 & 2003 - 08 - 27 & 2400 & c & 680 & 0.46 & 22.78 & 1905 + 03d4cn & 22:16:34.600 & -17:16:13.55 & 2003 - 08 - 27 & 4800 & c & 720 & 0.46 & 23.81 & 49 + 03d4cy & 22:13:40.460 & -17:40:53.90 & 2003 - 09 - 26 & 5400 & n+s & 720 & 0.59 & 24.19 & 149 + 03d4cz & 22:16:41.870 & -17:55:34.54 & 2003 - 09 - 27 & 3600 & c & 720 & 0.41 & 24.41 & 15 + 03d4fd & 22:16:14.471 & -17:23:44.37 & 2003 - 10 - 24 & 3600 & n+s & 720 & 0.67 & 23.61 & 321 + 03d4fe & 22:16:08.844 & -17:55:19.21 & 2003 - 10 - 24 & 3600 & n+s & 720 & 0.48 & 23.58 & 66 + 03d4gl & 22:14:44.177 & -17:31:44.47 & 2003 - 10 - 29 & 3600 & n+s & 720 & 0.63 & 23.43 & 121 + 04d1de & 02:26:35.925 & -04:25:21.65 & 2004 - 08 - 17 & 7200 & n+s & 720 & 0.51 & 23.63 & 56 + 04d1dr & 02:27:23.905 & -04:51:27.43 & 2004 - 08 - 14 & 5400 & n+s & 720 & 0.57 & 24.28 & 72 + 04d1hd & 02:26:08.850 & -04:06:35.22 & 2004 - 09 - 13 & 2400 & c & 680 & 0.85 & 22.16 & 1254 + 04d1ho & 02:24:44.856 & -04:39:15.55 & 2004 - 09 - 16 & 3600 & c & 720 & 0.59 & 23.13 & 24 + 04d1hy & 02:24:08.678 & -04:49:52.22 & 2004 - 09 - 11 & 5400 & n+s & 720 & 0.73 & 23.53 & 996 + 04d1jf & 02:25:18.914 & -04:49:09.05 & 2004 - 10 - 13 & 2400 & c & 680 & 0.92 & 22.94 & 19 + 04d1ln & 02:25:53.482 & -04:27:03.75 & 2004 - 10 - 17 & 2400 & c & 680 & 0.62 & 22.80 & 29 + 04d1ow & 02:26:42.708 & -04:18:22.55 & 2004 - 11 - 08 & 5400 & n+s & 720 & 0.69 & 23.87 & 4201 + 04d2aa & 10:02:02.100 & + 02:40:51.76 & 2004 - 01 - 23 & 7320 & n+s & 720 & 0.58 & 24.19 & + 04d2ad & 10:00:08.093 & + 02:39:01.40 & 2004 - 01 - 22 & 7320 & n+s & 720 & 0.54 & 24.17 & + 04d2ae & 10:01:52.414 & + 02:13:21.11 & 2004 - 01 - 21 & 5490 & n+s & 720 & 0.75 & 23.64 & + 04d3aa & 14:16:49.935 & + 52:45:31.12 & 2004 - 01 - 30 & 5400 & n+s & 720 & 1.02 & 24.05 & 12 + 04d3ae & 14:22:21.569 & + 52:21:39.21 & 2004 - 01 - 25 & 2400 & c & 680 & 0.94 & 23.10 & 196 + 04d3ax & 14:22:39.072 & + 52:51:52.57 & 2004 - 01 - 28 & 5400 & n+s & 720 & 1.30 & 24.95 & 246 + 04d3bf & 14:17:45.096 & + 52:28:04.31 & 2004 - 02 - 17 & 2700 & c & 680 & & 23.16 & + 04d3dd & 14:17:48.431 & + 52:28:14.72 & 2004 - 04 - 25 & 5400 & n+s & 720 & 0.59 & 24.06 & 375 + 04d3de & 14:22:13.503 & + 52:17:09.71 & 2004 - 04 - 27 & 7200 & n+s & 720 & 0.57 & 24.01 & 651 + 04d3fj & 14:19:50.703 & + 52:41:31.84 & 2004 - 04 - 28 & 7200 & n+s & 720 & 0.72 & 24.19 & 108 + 04d3fq & 14:16:57.906 & + 52:22:46.53 & 2004 - 04 - 26 & 5400 & n+s & 720 & 0.97 & 23.04 & 412 + 04d3gu & 14:22:07.359 & + 52:38:54.60 & 2004 - 05 - 22 & 4800 & c & 720 & 1.03 & 22.60 & 6 + 04d3gx & 14:20:13.678 & + 52:16:58.60 & 2004 - 05 - 21 & 7200 & n+s & 720 & 0.40 & 24.38 & 2439 + 04d3hn & 14:22:06.878 & + 52:13:43.46 & 2004 - 05 - 22 & 4800 & c & 720 & 0.47 & 22.94 & 14 + 04d3kr & 14:16:35.937 & + 52:28:44.20 & 2004 - 06 - 16 & 2400 & c & 680 & 0.82 & 21.60 & 156 + 04d3lp & 14:19:50.927 & + 52:30:11.85 & 2004 - 05 - 27 & 5400 & n+s & 720 & 0.52 & 24.45 & 78 + 04d3lu & 14:21:08.009 & + 52:58:29.74 & 2004 - 06 - 23 & 3600 & n+s & 720 & 0.84 & 23.49 & 17 + 04d3mk & 14:19:25.830 & + 53:09:49.56 & 2004 - 06 - 19 & 4320 & n+s & 720 & 1.25 & 23.27 & 86 + 04d3ml & 14:16:39.107 & + 53:05:35.66 & 2004 - 06 - 20 & 3600 & n+s & 720 & 0.41 & 23.90 & 2252 + 04d3nc & 14:16:18.224 & + 52:16:26.09 & 2004 - 07 - 13 & 2400 & c & 720 & 0.66 & 23.39 & 149 + 04d3nh & 14:22:26.729 & + 52:20:00.92 & 2004 - 06 - 23 & 1800 & c & 680 & 0.80 & 21.66 & 199 + 04d3nq & 14:20:19.193 & + 53:09:15.90 & 2004 - 07 - 14 & 1500 & c & 680 & 0.61 & 21.03 & 10000 + 04d3nr & 14:22:38.526 & + 52:38:55.89 & 2004 - 07 - 15 & 7200 & n+s & 720 & 0.69 & 24.40 & 2300 + 04d3ny & 14:18:56.332 & + 52:11:15.06 & 2004 - 07 - 10 & 5400 & n+s & 720 & 0.79 & 23.23 & 203 + 04d3oe & 14:19:39.381 & + 52:33:14.21 & 2004 - 07 - 11 & 3600 & n+s & 720 & 0.62 & 23.21 & 28 + 04d3og & 14:20:39.748 & + 53:01:15.02 & 2004 - 07 - 19 & 2700 & c & 720 & 1.10 & 21.81 & 151 + 04d3pd & 14:22:33.506 & + 52:13:47.77 & 2004 - 07 - 18 & 3600 & n+s & 720 & 0.83 & 23.34 & 72 + 04d4 dm & 22:15:25.470 & -17:14:42.71 & 2004 - 07 - 18 & 3600 & n+s & 720 & 0.96 & 23.55 & 123 + 04d4ec & 22:16:29.286 & -18:11:04.13 & 2004 - 07 - 19 & 3600 & n+s & 720 & 0.70 & 23.08 & 37 + 04d4 ft & 22:14:31.097 & -17:40:19.74 & 2004 - 08 - 12 & 3600 & c & 720 & 0.67 & 23.21 & 78 + 04d4gg & 22:16:09.268 & -17:17:39.98 & 2004 - 08 - 16 & 3600 & c & 720 & 0.81 & 23.03 & 30 + 04d4hu & 22:15:36.193 & -17:50:19.81 & 2004 - 09 - 18 & 5400 & n+s & 720 & 0.52 & 23.45 & 84 + 04d4hx & 22:13:40.587 & -17:23:03.35 & 2004 - 09 - 16 & 5400 & n+s & 720 & 0.73 & 24.15 & 25 + 04d4ic & 22:14:21.841 & -17:56:36.43 & 2004 - 09 - 12 & 5160 & n+s & 720 & 0.69 & 23.34 & 231 + 04d4ih & 22:17:17.041 & -17:40:38.74 & 2004 - 10 - 07 & 5400 & n+s & 720 & 0.52 & 23.95 & 41 + 04d4ii & 22:15:55.645 & -17:39:27.09 & 2004 - 09 - 15 & 7200 & n+s & 720 & 0.45 & 23.86 & 57 + 04d4im & 22:15:00.885 & -17:23:45.84 & 2004 - 10 - 10 & 7200 & n+s & 720 & 0.44 & 23.23 & 18 + 04d4jy & 22:13:51.605 & -17:24:18.13 & 2004 - 10 - 14 & 8881 & n+s & 720 & 0.77 & 24.08 & 1779 + 04d4kn & 22:15:04.324 & -17:19:45.05 & 2004 - 10 - 19 & 5400 & n+s & 720 & 0.60 & 23.74 & 97 + llllcrrrll 03d1as & 0.872 & 0.001 & sn : & 2 & & & & : + 03d1ax & 0.496 & 0.001 & sn ia & 5 & -3.0 & 0.1 & -3.3 & h&k + 03d1bk & 0.8650 & 0.0005 & sn ia & 5 & -6.3 & 0.1 & -2.1 & h&k , h@xmath45 , h@xmath46 + 03d1cj & 0.364 & 0.001 & sn ib / c : & 1 & & & & h@xmath47 , + 03d1 cm & 0.87 & 0.02 & sn ia & 4 & -5.0 & 0.3 & 2.4 & sn + 03d1co & 0.68 & 0.01 & sn ia & 5 & -4.8 & 0.3 & -1.2 & sn + 03d1ew & 0.868 & 0.001 & sn ia & 5 & 0.9 & 0.4 & -0.2 & + 03d1fp & 0.270 & 0.001 & sn iib & 0 & & & & h@xmath47 , h@xmath45 , , , + 03d1fq & 0.80 & 0.02 & sn ia & 4 & -1.6 & 0.3 & 2.2 & sn + 03d4cj & 0.27 & 0.01 & sn ia & 5 & -9.7 & 0.1 & -6.9 & sn + 03d4ck & 0.189 & 0.001 & sn iin & 0 & & & & sn + 03d4cn & 0.818 & 0.001 & sn ia & 4 & -0.5 & 0.6 & 2.8 & , , h@xmath45 + 03d4cy & 0.9271 & 0.0005 & sn ia & 4 & 5.3 & 0.3 & 7.7 & + 03d4cz & 0.695 & 0.001 & sn ia & 4 & 9.4 & 0.1 & 8.7 & h&k , g - band + 03d4fd & 0.791 & 0.003 & sn ia & 5 & -1.6 & 0.3 & -1.5 & + 03d4fe & ? & & sn : & 1 & & & & + 03d4gl & 0.56 & 0.01 & sn ia & 4 & -9.0 & 0.2 & -6.0 & sn + 04d1de & 0.7677 & 0.0002 & sn ia * & 3 & -6.8 & 0.1 & -4.5 & , , h@xmath45 , poss h&k + 04d1dr & 0.6414 & 0.0003 & sn : & 2 & & & & , , h@xmath45 , h@xmath46 + 04d1hd & 0.3685 & 0.0005 & sn ia & 5 & -4.8 & 0.1 & -4.0 & , weak + 04d1ho & 0.7012 & 0.0004 & sn & 2 & & & & , , h&k , h@xmath45 , h@xmath46 + 04d1hy & 0.85 & 0.02 & sn ia & 5 & -3.5 & 0.3 & -3.2 & sn + 04d1jf & 0.3800 & 0.0002 & sn : & 2 & & & & , , h@xmath45 + 04d1ln & 0.2072 & 0.0002 & sn ii - p & 0 & & & & h@xmath47 , , + 04d1ow & 0.93 & 0.02 & sn ia & 4 & 2.6 & 0.2 & -0.8 & sn + 04d2aa & ? & & sn : & 2 & & & & + 04d2ad & 0.6802 & 0.0002 & sn : & 2 & & & & , , h@xmath45 + 04d2ae & 0.843 & 0.001 & sn ia & 4 & 0.0 & 0.1 & -1.5 & h&k + 04d3aa & 0.2045 & 0.0002 & sn ii & 0 & & & & h@xmath47 , h@xmath45 , , + 04d3ae & 0.217 & 0.001 & sn ii & 0 & & & & h@xmath47 , + 04d3ax & 0.3558 & 0.0002 & sn ii : & 1 & & & & h@xmath47 , h@xmath45 , + 04d3bf & 0.1560 & 0.0005 & sn ia & 5 & & & 15.1 & , , , h@xmath47 , h@xmath45 + 04d3dd & 1.01 & 0.02 & sn ia & 4 & 2.9 & 0.3 & -1.4 & sn + 04d3de & ? & & sn ii - p & 0 & & & & + 04d3fj & ? & & sn : & 1 & & & & + 04d3fq & 0.73 & 0.01 & sn ia & 4 & 0.8 & 0.3 & 3.6 & sn + 04d3gu & 0.748 & 0.001 & sn : & 2 & & & & h&k , balmer , weak + 04d3gx & 0.91 & 0.02 & sn ia * & 3 & 10.8 & 0.2 & 8.3 & sn + 04d3hn & 0.5516 & 0.0003 & sn ia & 5 & 7.2 & 0.1 & 4.9 & h&k , balmer + 04d3kr & 0.3373 & 0.0002 & sn ia & 5 & 4.4 & 0.1 & 1.7 & , , h@xmath45 + 04d3lp & 0.983 & 0.001 & sn ia * & 3 & 1.0 & 0.2 & -1.2 & + 04d3lu & 0.8218 & 0.0002 & sn ia & 4 & 5.5 & 0.1 & 5.6 & h&k + 04d3mk & 0.813 & 0.001 & sn ia & 5 & -2.4 & 0.1 & 1.2 & , h&k + 04d3ml & 0.95 & 0.02 & sn ia & 4 & -1.8 & 0.3 & 1.1 & sn + 04d3nc & 0.817 & 0.001 & sn ia * & 3 & 7.2 & 0.2 & & poss + 04d3nh & 0.3402 & 0.0002 & sn ia & 5 & 3.5 & 0.1 & 3.7 & h@xmath47 , h@xmath45 , , poss h&k + 04d3nq & 0.22 & 0.01 & sn ia & 5 & 8.1 & 0.1 & 8.8 & sn + 04d3nr & 0.96 & 0.02 & sn ia * & 3 & 8.1 & 0.3 & 3.9 & sn + 04d3ny & 0.81 & 0.02 & sn ia & 5 & 1.6 & 0.2 & 2.5 & sn + 04d3oe & 0.756 & 0.001 & sn ia & 4 & 1.4 & 0.1 & 1.8 & h&k + 04d3og & 0.352 & 0.001 & sn & 2 & & & & h@xmath47 , h@xmath45 , , , + 04d3pd & 0.760 & 0.001 & sn : & 2 & & & & h@xmath45 , , + 04d4 dm & 0.811 & 0.001 & sn ia & 4 & 2.7 & 0.2 & -0.7 & , + 04d4ec & 0.593 & 0.001 & sn : & 2 & & & & , , h@xmath45 , h@xmath46 + 04d4 ft & 0.2666 & 0.0002 & sn & 2 & & & & , h@xmath47 , h@xmath45 + 04d4gg & 0.4238 & 0.0004 & sn ia & 5 & -9.7 & 0.1 & -10.0 & , , h@xmath47 , h@xmath45 , h@xmath46 + 04d4hu & 0.7027 & 0.0003 & sn ia & 5 & 5.2 & 0.5 & 5.0 & , , h@xmath45 + 04d4hx & 0.545 & 0.005 & sn : & 2 & & & & 4000 break , poss h&k + 04d4ic & 0.68 & 0.02 & sn ia & 4 & 2.5 & 0.3 & 4.8 & sn + 04d4ih & 0.934 & 0.001 & sn ia * & 3 & 8.7 & 0.2 & 5.6 & , h&k , some balmer + 04d4ii & 0.866 & 0.001 & sn ia & 5 & -4.6 & 0.2 & -3.5 & + 04d4im & 0.7510 & 0.0005 & sn ia & 4 & 0.7 & 0.2 & 0.2 & h&k , h@xmath48 + 04d4jy & 0.93 & 0.02 & sn ia * & 3 & 2.0 & 0.4 & 0.0 & sn + 04d4kn & 0.9095 & 0.0005 & sn : & 2 & & & & , h&k , balmer +

the snls is an ongoing five year project with the goal of measuring the equation of state of dark energy by discovering and following over 700 high - redshift sne ia using data from the canada - france - hawaii telescope legacy survey . is found to be host galaxy contamination of the spectrum when the sn was at least as bright as the underlying host galaxy the target was identified more than 90% of the time . however when the image quality was better than 0.55 , the candidate was identified 88% of the time . over the five - year course of the survey , using the selection techniques presented here we will be able to add more confirmed sne ia than would be possible using previous methods .

we present new techiques for improving the efficiency of supernova ( sn ) classification at high redshift using 64 candidates observed at gemini north and south during the first year of the supernova legacy survey ( snls ) . the snls is an ongoing five year project with the goal of measuring the equation of state of dark energy by discovering and following over 700 high - redshift sne ia using data from the canada - france - hawaii telescope legacy survey . we achieve an improvement in the sn ia spectroscopic confirmation rate : at gemini 71% of candidates are now confirmed as sne ia , compared to 54% using the methods of previous surveys . this is despite the comparatively high redshift of this sample , where the median sn ia redshift is ( ) . these improvements were realized because we use the unprecedented color coverage and lightcurve sampling of the snls to predict whether a candidate is an sn ia and estimate its redshift , before obtaining a spectrum , using a new technique called the `` sn photo - z . '' in addition , we have improved techniques for galaxy subtraction and sn template fitting , allowing us to identify candidates even when they are only 15% as bright as the host galaxy . the largest impediment to sn identification is found to be host galaxy contamination of the spectrum when the sn was at least as bright as the underlying host galaxy the target was identified more than 90% of the time . however , even sne on bright host galaxies can be easily identified in good seeing conditions . when the image quality was better than 0.55 , the candidate was identified 88% of the time . over the five - year course of the survey , using the selection techniques presented here we will be able to add more confirmed sne ia than would be possible using previous methods .

astro-ph0205389

i

it is now understood that intrinsic absorption is a common phenomenon in seyfert 1 galaxies , present in more than half of those observed with the spectrographs aboard the _ hubble space telescope ( hst ) _ ( crenshaw et al . 1999 ) . among those seyferts that show absorption , high ionization resonance lines such as n v @xmath81238.8 , 1242.8 and c iv @xmath81548.2 , 1550.8 are always present , along with ly@xmath4 , while lower ionization lines , such as si iv @xmath81393.8 , 1402.8 , and mg ii @xmath82796.3 , 2803.5 , are less common . the absorption lines can be blueshifted ( by up to 2100 km s@xmath6 ) with respect to the systemic velocities of the host galaxies , indicating net radial outflow . however , uv absorption lines can arise in dusty gas within the plane of the host galaxy ( crenshaw et al . 2001 ; crenshaw et al . 2002 ) ; these are often saturated and at velocities close to systemic . the ionic columns can be highly variable , which may be the result of changes in response to the ionizing continuum , as first suggested in case of ngc 4151 by bromage et al . ( 1985 ) and espey et al . ( 1998 ) , and discussed in detail in crenshaw et al . ( 2000a ) and kraemer et al . ( 2001a ) , or transverse motion , as appears to be the case for ngc 5548 and ngc 3783 ( crenshaw & kraemer 1999 ; kraemer , crenshaw , & gabel 2001b ) . in fact , both mechanisms may be at work in individual agn . in either case , the variability is indicative of the promixity of the absorbers to the central active nucleus of these galaxies ; in the case of ngc 4151 , constraints on the density and ionization of the strongest absorption system place it within 0.03 pc of the continuum source ( kraemer et al . 2001a ) . the presence of intrinsic absorption , typically in the form of bound - free edges of o vii and o viii , has been detected in the x - ray spectra of a similar fraction of seyfert 1 galaxies ( reynolds 1997 ; george et al . most recently , spectra obtained with the _ chandra x - ray observatory ( cxo ) _ have revealed that x - ray absorption lines associated with this material are also blue - shifted ( kaastra et al . 2000 ; kaspi et al . 2000 , collinge et al . the connection between the x - ray and uv absorption is complex and there is likely a range of physical conditions within the absorbers ( see kriss et al . 1996a ; kriss et al . 2000 ; krolik & kriss 2001 ) . furthermore , there is evidence that the x - ray absorbers in some sources must also be multi - zoned ( otani et al . 1996 ; reynolds et al . 1997 ) . ngc 3516 ( @xmath9 @xmath10 0.00875 ) is one of the few seyfert 1 galaxies with uv absorption lines , specifically n v , c iv , and si iv , strong enough to have been detected with the _ international ultraviolet explorer ( iue ) _ ( ulrich & boisson 1983 ) . these lines are known to vary on timescales as short as weeks ( voit , shull , & begelman 1987 : walter et al . 1990 ; kolman , halpern , & martin 1993 ) . walter et al . suggested that the c iv absorption consists of a narrow , apparently stable component in the core of the broad emission lines and a variable , broad , blue - shifted component . koratkar et al . ( 1996 ) found the blueshifted component present in _ spectra in 1978 , but it had disappeared between 1989 and 1993 , and has been absent in subsequent _ hopkins ultraviolet telescope _ ( hut ) ( kriss et al . 1996b ) and _ hst_/goddard high resolution spectrograph ( ghrs ) ( crenshaw , maran , & mushotzky 1998 ) observations . based on ghrs spectra , crenshaw et al . ( 1998 ) determined that the absorption in the core of the line ( walter et al.s `` stable '' component ) consisted of two broad components , with velocities of @xmath5380 and @xmath5 150 km s@xmath6 , and two narrow components at @xmath590 and @xmath530 km s@xmath6 . ngc 3516 also exhibits strong , variable x - ray absorption ( kolman et al . 1993 ; nandra & pounds 1994 ; kriss et al . 1996a ; mathur , wilkes , & aldcroft 1997 ) . although mathur et al . ( 1997 ) suggested that the x - ray and uv absorption arises in gas characterized by a single set of physical conditions , kriss et al . ( 1996a ) modeled the x - ray absorber as two zones , one with an ionization parameter ( the ratio of the density of photons with energies @xmath11 13.6 ev to the number density of hydrogen atoms at the illuminated face of the zone ) u @xmath10 1.66 and a total hydrogen column density of 1.4 x 10@xmath12 @xmath13 and a lower ionization zone with u @xmath10 0.32 and a total column density of 6.9 x 10@xmath14 @xmath13 , and argued that not all of the uv lines could form in these zones . in our previous paper ( netzer et al . 2002 ; hereafter paper i ) , we presented an analysis of the _ cxo_/low energy transmission grating spectrograph ( letgs ) spectrum obtained on 2000 october 6 . the x - ray continuum flux , flux@xmath15 @xmath10 ( 1.6 @xmath16 0.2 ) x 10@xmath17 photons @xmath13 s@xmath6 kev@xmath6 , was close to its historic minimum , roughly a factor of 8 10 below maximum ( observed in 1994 with _ asca _ ) . we found that the variations in observed flux and spectra at these epochs is consistent with an absorber of constant column density ( 7.9 x 10@xmath14 @xmath13 ) whose ionization state has changed in response to the variation in the ionizing continuum , specifically : for the current low flux state , u @xmath10 0.19 , while it would be a factor of 8 to 10 higher in the high flux state ( depending on the amplitude of the uv continuum variations ) , in rough agreement with the high ionization component described by kriss et al . ( 1996a ) . the model predicts large column densities ( @xmath3 10@xmath18 @xmath13 ) for n v and c iv , hence one or more of the observed kinematic components of the uv absorption should be associated with the x - ray absorber . we obtained echelle spectra of ngc 3516 with the space telescope imaging spectrograph ( stis ) on hst under a stis guaranteed time observer program . in this paper , we present our analysis of the physical conditions in the uv absorbers , nature of their variability , and the connection to the x - ray absorption detected in our contemporaneous _ cxo_/letgs observation .

the uv continuum was times lower than that observed during 1995 with the goddard high resolution spectrograph ( ghrs ) , and the x - ray flux from a contemporaneous _ chandra x - ray observatory ( cxo ) _ observation was a factor of below that observed with _ we have achieved an acceptable fit to the x - ray data using the combined x - ray opacity of the uv components 1 , 2 and 3 . by increasing the uv and x - ray fluxes of these models to match the previous high states , we are able to match the ghrs c iv column densities , absence of detectable c iv absorption in components 5 through 8 , and the 1994 _ asca _ spectrum . we conclude that variability of the uv and x - ray absorption in ngc 3516 is primarily due to changes in the ionizing flux .

we present observations of the uv absorption lines in the seyfert 1 galaxy ngc 3516 , obtained at a resolution of/ 40,000 with the space telescope imaging spectrograph ( stis ) on 2000 october 1 . the uv continuum was times lower than that observed during 1995 with the goddard high resolution spectrograph ( ghrs ) , and the x - ray flux from a contemporaneous _ chandra x - ray observatory ( cxo ) _ observation was a factor of below that observed with _ asca_. the stis spectra show kinematic components of absorption in ly , c iv , and n v at radial velocities of , , and km s ( components 1 , 2 , and 3 , respectively ) , which were detected in the earlier ghrs spectra ; the last of these is a blend of two ghrs components that have increased greatly in column density . four additional absorption components have appeared in the stis spectra at radial velocities of , , , and km s ( components 5 through 8) ; these may also have been present in earlier low - flux states observed by the _ international ultraviolet explorer ( iue)_. based on photoionization models , we suggest that the components are arranged in increasing radial distance in the order , 3 , 2 , 1 , followed by components 5 8 . we have achieved an acceptable fit to the x - ray data using the combined x - ray opacity of the uv components 1 , 2 and 3 . by increasing the uv and x - ray fluxes of these models to match the previous high states , we are able to match the ghrs c iv column densities , absence of detectable c iv absorption in components 5 through 8 , and the 1994 _ asca _ spectrum . we conclude that variability of the uv and x - ray absorption in ngc 3516 is primarily due to changes in the ionizing flux .

astro-ph0205389

c

we have shown that our model for the uv absorbers , with the components arranged in increasing radial distance and each covering the continuum source , accurately predicts most of the ionic columns and the x - ray opacity . given the success of the model , we may use it as a starting point to unravel the geometry of the circumnuclear gas . in paper i , based on the recombination timescale for o vii , we placed a conservative lower limit on the density of x - ray absorber of n@xmath21 @xmath11 2 x 10@xmath49 @xmath50 . for component 1b , we predict that n@xmath51 @xmath10 1.87 x 10@xmath38 @xmath13 . the lack of detection of c iii@xmath52 1175 is indicative of n@xmath53 @xmath54 a few x 10@xmath55 @xmath13 . for t @xmath3 2.0 x 10@xmath56k , this ratio of n@xmath53/n@xmath51 corresponds to a density of @xmath54 10@xmath57 @xmath13 ( bromage et al . 1985 ; kriss et al . if the high - ionization core components are co - located with component 1b , their higher ionization parameters require that they have densities of @xmath54 10@xmath58 @xmath50 . alternatively , for component 1a , we predict that n@xmath51 @xmath10 9.43 x 10@xmath38 @xmath13 . based on the upper limit for n@xmath53 , the density of component 1a is @xmath59 10@xmath60 @xmath50 . hence , we derive a loose upper limit of n@xmath21 @xmath54 10@xmath61 @xmath50 for the density of the high - ionization core components . given our estimate of the continuum luminosity and the constraints on the densities of the absorbers , the core components must lie between 5.4 x 10@xmath62 cm and 1.2 x 10@xmath63 cm from the central source . this range in radial distance is consistent with full - covering of the broad c iv emission region , which has a radius of @xmath3 4.5 light - days ( koratkar et al . 1996 ) . by comparison , kraemer et al . ( 2001a ) estimated that the high density ( n@xmath21 @xmath11 10@xmath60 @xmath50 ) uv absorber detected in ngc 4151 , component d@xmath7e , must lie at a distance of @xmath54 6.2 x 10@xmath62 cm from the central source ( assuming h@xmath34 @xmath10 75 km s@xmath6 mpc@xmath6 ) . hence , the radial distance of the absorbing gas in ngc 3516 is roughly consistent with that in ngc 4151 , although possibly somewhat further from the central source and , apparently , less dense . on average , the absorbers are in a much higher ionization state than component d@xmath7e , for which u @xmath10 0.015 . since the ionizing luminosity of ngc 3516 is only a factor of @xmath3 2 greater than ngc 4151 , observed in similar low - flux states , the greater ionization state must be mostly due to the lower density . another interesting difference is the weakness of the scattered light in the troughs of the saturated absorption lines in ngc 3516 : @xmath59 5% of the low - state continuum flux , compared to @xmath11 50% of the low - state flux in ngc 4151 ( kraemer et al . for ngc 4151 , we argued that the scattered light consisted of continuum @xmath7 broad - line emission , reflected into our line - of - sight by free electrons in a component of highly ionized gas that extended beyond the region covered by the absorbers . either this component is weaker in ngc 3516 , the absorbers are covering more of the scattering region , or the scattering region is further away from the nucleus ( outside our projected aperture ) . the observed emission - line fluxes can be used to constrain the global covering factor of the absorbers . the observed c iv @xmath0 1550 flux is @xmath2 2.37 x 10@xmath64 ergs @xmath13 s@xmath6 , or l@xmath40 @xmath2 3.5 x 10@xmath65 ergs s@xmath6 . for a density of n@xmath21 @xmath10 10@xmath58 @xmath50 , the radial distance of component 3@xmath74 is r @xmath10 1.7 x 10 @xmath18 cm and the predicted c iv flux at the illuminated surface of the 4 core component models absorbers is 1.5 x 10@xmath49 ergs @xmath13 s@xmath6 , hence , the covering factor must be @xmath24 0.64 . interestingly , in its current low - flux state , approximately 50% of the c iv emission is from a component with fwhm of @xmath3 1500 km s@xmath6 ( see figure 2 and hutchings et al . [ 2001 ] ) , which is characteristic of the so - called intermediate line region ( ilr ; wills et al . [ 1993 ] ) . if the absorbers are the source of the ilr emission , the covering factor is @xmath3 0.3 . note , that although the core components cover both the broad and intermediate line contributions to the c iv emission , this does not imply that they must lie outside the ilr . for example , self - absorption by the ilr gas could occur in an expanding shell ( see hutchings et al . if the absorption arises in the ilr , the ilr gas has a significant radial velocity component , similar to the emission - line gas in the inner nlr of other seyfert galaxies ( crenshaw & kraemer 2000 ; kaiser et al . 2000 ; crenshaw et al . 2000b ; ruiz et al . 2001 ) . a connection between the ilr and nlr components has been suggested by sulentic & marziani ( 1999 ) , although our results suggest that the ilr could extend to the outer edge of the blr . from our estimate of the intrinsic reddening ( see section 4.1 ) , one would infer that there is a component of dusty gas of column density n@xmath21 @xmath3 3 x 10@xmath30 @xmath13 along our line - of - sight to the nucleus of ngc 3516 . note that this is based on assumption of a galactic dust / gas ratio ; if the ratio were lower , the column would be larger . as shown in kraemer et al . ( 2000 ) and crenshaw et al . ( 2001 ) , uv absorption lines can form in dusty gas surrounding an agn . typically , one would expect strong c iv lines from a column of this size . hence , either the absorption lines associated with the dusty column are buried in the troughs of the core components , or the dust exists in one or more of these absorbers . following barvainis ( 1987 ) , we can estimate the dust sublimation radius , i.e , the point interior to which dust grains would evaporate . during its low - flux state , the ionizing luminosity of the central source is @xmath3 1.4 x 10@xmath66 ergs s@xmath6 . assuming an average luminosity a factor of 3 greater ( see section 2.3 ) , and a dust sublimation temperature of 1500 k ( salpeter 1977 ) , the sublimation radius for ngc 3516 is @xmath54 2.6 x 10@xmath18 cm , or , roughly the same radial distance as the core components . although the absorbers are radially outflowing , we do not know their starting point , or whether they were well - shielded from the continuum source by intervening gas . hence it is possible that some grains have survived within them . alternatively , some dust could have been swept - up by the absorbers as they move outwards . if , for example , the dust were within component 1 , it may help explain the overprediction of mg ii ( section 4.1 ) . furthermore , since the column density of component 1 is roughly 5 times larger than our dusty column , the dust / gas ratio could be 20% the galactic ratio ( indicative of the harsh conditions close to the active nucleus ) , and still produce the observed reddening . in any case , although it is possible the dust is in a heretofore undetected component of gas , we suggest that the reddening may be due to a small amount of dust within one or more of the core components . perhaps the most unusual aspect of the intrinsic absorption in seyfert galaxies is the lack of evidence for radial acceleration . in the case of ngc 4151 , weymann et al . ( 1997 ) attributed this to the large radial distances of the absorbers . however , in kraemer et al . ( 2001a ) we determined that component d@xmath7e was close enough to the central source that it should undergo a detectable acceleration . to explain this , we suggested that the large column density and optical thickness of d@xmath7e would make radiative acceleration inefficient ( see williams 1972 ; mathews 1974 ) . the physical conditions in the core components of ngc 3516 are similar to d@xmath7e , hence the absence of detectable changes in radial velocities between 1995 and the present is understandable , although it is interesting that the blueshifted components , which only appear during lowstates , appear at generally the same velocities , and these are clearly optically thin ( of course , the radial acceleration of the absorbers may simply be too small to detect in the @xmath3 6 years between the ghrs and stis observations ) . another explanation is that the absorbers are not simply radially ( or even radiatively ) accelerated . disk - wind models ( e.g. , konigl & kartje 1994 ) require that the gas in the outflow must first be levitated off the accretion disk . bottorff , korista , & shlosman ( 2000 ) have modeled the absorbers as part of a magnetohydromagnetic wind , which has a strong non - radial component . elvis ( 2000 ) has also proposed an outflow scenario that includes a non - radial component . if the absorption arises in disk - driven wind , the gas would have a strong transverse component of velocity . however our analysis ( see also paper i ) suggests strongly that the variability of the absorption in ngc 3516 results from changes in ionization state due to the variable luminosity of the central source , rather than changes in column density due to transverse motion . one possibility is that the individual kinematic components are associated with different flow tubes or shells along our line - of - sight , which would originate at different radial positions at the base of the wind . since the total column density within the absorber does not appear to change , the amount of gas within these tubes must be fairly constant , although this does not imply confinement but , rather , a continuous flow . although the source luminosity changes dramatically , the flow density appears to be independent of the short - term changes in the flux , which may imply that it is not radiatively driven off the disk ( see , again , bottorff et al . 2000 ) . interestingly , in our model the radial velocities of components 1 through 5 increase with distance from the central source . this would be expected if they each originated at the roughly the same distance , and have been continuously accelerated , e.g. , via resonance line driving or some other radiative mechanism . however , the velocities can also depend on the radial distance at which the different components originated , hence a range in velocities may not be an indication of acceleration , but of different `` launch - pads '' for the components of the flow . another interesting aspect of the uv absorbers is their apparent stability ; the core components vary in ionization state but have shown evidence for significant c iv columns for two decades . as discussed in krolik , mckee , & tarter ( 1981 ) and , more recently , in krolik & kriss ( 2001 ) , there are two regimes of ionization ( characterized by the `` pressure '' ionization parameter , or u / t ) and temperature wherein a cloud of photoionized gas is stable to thermal perturbations : at low ionization / temperature , when line cooling is efficient , and at high temperature / ionization , when thermal balance is achieved via compton processes . in the intermediate region , small changes in ionization can result in large changes in temperature . although the exact relationship between u / t and t for a model nebula depends on the sed of the continuum radiation , including the non - ionizing continuum which is critical in the compton regime , and the atomic parameters , such as collision strengths , instability typically occurs between 5 x 10@xmath56 k and 10@xmath67 k. both our low- and high - state models for the core components predict that these absorbers remain thermally stable , which may help explain their continuing presence . on the other hand , the blueshifted components may not be stable . in figure 7 , we show the instability curve for the screened sed used for the models of the blueshifted components . in the current low - state , component 5 is in the low - temperature stable regime , while the more highly ionized components lie along the vertical , quasi - stable , region ( unstable regions are places where @xmath68 ) . this implies that these components have experienced large temperature fluctuations in response to the changes in ionizing flux , which may explain part of the discrepant model predictions . perhaps most of this gas is in the compton - cooled state , out of which uv absorbers condense when the continuum flux drops sufficiently . the variable opacity of the intervening core components amplifies the changes in ionizing flux and , hence , thermal perturbations of the blueshifted components .

four additional absorption components have appeared in the stis spectra at radial velocities of , , , and km s ( components 5 through 8) ; these may also have been present in earlier low - flux states observed by the _ international ultraviolet explorer ( iue)_. based on photoionization models , we suggest that the components are arranged in increasing radial distance in the order , 3 , 2 , 1 , followed by components 5 8 .

we present observations of the uv absorption lines in the seyfert 1 galaxy ngc 3516 , obtained at a resolution of/ 40,000 with the space telescope imaging spectrograph ( stis ) on 2000 october 1 . the uv continuum was times lower than that observed during 1995 with the goddard high resolution spectrograph ( ghrs ) , and the x - ray flux from a contemporaneous _ chandra x - ray observatory ( cxo ) _ observation was a factor of below that observed with _ asca_. the stis spectra show kinematic components of absorption in ly , c iv , and n v at radial velocities of , , and km s ( components 1 , 2 , and 3 , respectively ) , which were detected in the earlier ghrs spectra ; the last of these is a blend of two ghrs components that have increased greatly in column density . four additional absorption components have appeared in the stis spectra at radial velocities of , , , and km s ( components 5 through 8) ; these may also have been present in earlier low - flux states observed by the _ international ultraviolet explorer ( iue)_. based on photoionization models , we suggest that the components are arranged in increasing radial distance in the order , 3 , 2 , 1 , followed by components 5 8 . we have achieved an acceptable fit to the x - ray data using the combined x - ray opacity of the uv components 1 , 2 and 3 . by increasing the uv and x - ray fluxes of these models to match the previous high states , we are able to match the ghrs c iv column densities , absence of detectable c iv absorption in components 5 through 8 , and the 1994 _ asca _ spectrum . we conclude that variability of the uv and x - ray absorption in ngc 3516 is primarily due to changes in the ionizing flux .

1505.05289

i

calculation of the @xmath0 decay amplitudes is very important to quantitatively understand the @xmath1 rule in the decay of the neutral @xmath16 meson system and to theoretically predict the direct @xmath17 violation parameter ( @xmath18 ) from the standard model . a direct lattice qcd calculation of the decay amplitudes for the @xmath19 process has been attempted for a long time . recently , the rbc - ukqcd collaboration presented the results at the physical quark mass in ref . @xcite , and those in the continuum limit in ref . @xcite in the physical kinematics , where the pions in the final state have finite momenta . they used the domain wall fermion action which preserves chiral symmetry on the lattice . a direct calculation of the decay amplitudes for the @xmath1 process has been unsuccessful for a long time , due to large statistical fluctuations from the disconnected diagrams . a first direct calculation was reported by the rbc - ukqcd collaboration in ref . @xcite at a lattice spacing @xmath20 and a pion mass @xmath21 on a @xmath22 lattice with the domain wall fermion action . they also presented a result at a smaller quark mass ( @xmath23 ) on a @xmath24 lattice with the same fermion action at lattice 2011 @xcite . in these two calculations , the kinematics was a @xmath16 meson at rest decaying to two zero momentum pions at an unphysical quark mass satisfying @xmath3 . the rbc - ukqcd collaboration has since been attempting a direct calculation in the physical kinematics at the physical quark mass by utilizing @xmath25-parity boundary conditions . their preliminary result was reported at lattice 2014 @xcite . an aim of the present article is to report on our calculation of the @xmath0 decay amplitudes with the improved wilson fermion action for both the @xmath1 and @xmath2 processes . that such a calculation is feasible stems from a realization , as shown in the present article , that cps symmetry @xcite and its extensions @xcite ensure that mixings with four - fermion operators with wrong chirality are absent even for the wilson fermion action for the parity odd process in both channels . a mixing to a lower dimension operator does occur , which gives unphysical contributions to the amplitudes on the lattice . however , it can be nonperturbatively subtracted by imposing a renormalization condition @xcite . after the subtraction we can obtain the physical decay amplitudes by the renormalization factor having the same structure as for the chiral symmetry preserved case . a potential advantage with the wilson fermion action over chirally symmetric lattice actions such as the domain wall action is that the computational cost is generally smaller . hence , with the same amount of computational resources , a statistical improvement may be expected with the lattice calculation of the decay amplitudes , albeit this point has to be verified by actual calculations . in the present work , we consider the decay of @xmath16 meson to two zero momentum pions at an unphysical quark mass @xmath3 , as in refs . @xcite , as the first step of a study with the wilson fermion action . our calculations are carried out on a subset of gauge configurations previously generated by the pacs - cs collaboration with the iwasaki gauge action and the nonperturbatively @xmath5-improved wilson fermion action for @xmath4 flavors at @xmath26 on a @xmath9 lattice @xcite . the subset corresponds to the hopping parameters @xmath27 for the up and the down quark and @xmath28 for the strange quark . we further generate gauge configurations at the same parameters to improve the statistics . the total number of gauge configurations used in the present work is @xmath29 . the parameters determined from the hadron spectrum analysis are @xmath30 for the lattice spacing , @xmath31 for the lattice size , @xmath32 and @xmath33 for the pion and the @xmath16 masses . the energy of the two - pion state is shifted from @xmath34 by the two - pion interaction on the lattice . the energy difference between the initial @xmath16 meson and the final two - pion state takes a nonzero value , @xmath35 for the @xmath36 channel , and @xmath37 for the @xmath11 channel on these configurations . in the present work we assume that these mismatches of the energy give only small effects to the decay amplitudes . this paper is organized as follows . the @xmath0 decay amplitudes can be calculated from the product of the @xmath0 matrix elements of the @xmath38 four - fermion weak interaction operators and the wilson coefficient functions for the operator product expansion . in sec . [ sec : delta s=1 operators ] these four - fermion operators are introduced and the operator mixing among them for the wilson fermion action is discussed . in sec . [ sec : method ] we describe the method of calculation used in the present work . the simulation parameters are also given . we present our results in sec . [ sec : results ] , and compare them with those by the rbc - ukqcd collaboration and the experimental values . conclusions of the present work are given in sec . [ sec : conclusions ] . our calculations have been carried out on the pacs - cs computer and t2k - tsukuba at university of tsukuba , the k computer at the riken advanced institute for computational science , sr16000 at university of tokyo , and sr16000 at high energy accelerator research organization ( kek ) . our preliminary results have been reported at lattice 2013 and 2014 @xcite .

we present our result for the decay amplitudes for both the and processes with the improved wilson fermion action . expanding on the earlier works by bernard _ et al . _ and by donini _ et al . _ our calculations are carried out with gauge configurations generated with the iwasaki gauge action and nonperturbatively-improved wilson fermion action at , , and on a ( ) lattice . we obtain , for the first time with a wilson - type fermion action , that and for a matching scale . the dependence on the matching scale for these values is weak .

we present our result for the decay amplitudes for both the and processes with the improved wilson fermion action . expanding on the earlier works by bernard _ et al . _ and by donini _ et al . _ , we show that mixings with four - fermion operators with wrong chirality are absent even for the wilson fermion action for the parity odd process in both channels due to cps symmetry . therefore , after subtraction of an effect from the lower dimensional operator , a calculation of the decay amplitudes is possible without complications from operators with wrong chirality , as for the case with chirally symmetric lattice actions . as a first step to verify the possibility of calculations with the wilson fermion action , we consider the decay amplitudes at an unphysical quark mass . our calculations are carried out with gauge configurations generated with the iwasaki gauge action and nonperturbatively-improved wilson fermion action at , , and on a ( ) lattice . for the quark loops in the penguin and disconnected contributions in the channel , the combined hopping parameter expansion and truncated solver method work very well for variance reduction . we obtain , for the first time with a wilson - type fermion action , that and for a matching scale . the dependence on the matching scale for these values is weak .

1505.05289

c

in the present work we have shown that mixings with four - fermion operators with wrong chirality are absent even for the wilson fermion action for the parity odd process due to cps symmetry . therefore , after subtraction of an effect from the lower dimensional operator , a calculation of the decay amplitudes is possible without additional calculations for the operator with wrong chirality . this is the same situation for chirally symmetric lattice actions such as the domain wall action . a potential advantage with the wilson fermion action over chirally symmetric lattice actions is that the computational cost is generally smaller . hence , with the same amount of computational resources , a statistical improvement may be expected . as the first step of a study to verify the possibility of calculations , we considered the @xmath16 meson decay amplitude for both the @xmath1 and @xmath2 channels with the wilson fermion action at an unphysical quark mass @xmath3 . we have found that the stochastic method with the hopping parameter expansion technique and the truncated solver method are very efficient for variance reduction , yielding a first result for the @xmath11 amplitude with the wilson fermion action . we have been able to show a large enhancement of the @xmath1 process over that for the @xmath19 at our quark mass ( @xmath32 and @xmath33 ) . however , our result for @xmath415 , particularly for the imaginary part , still has a large statistical error so that we have not obtained a nonzero result for @xmath416 over the error . for the @xmath11 two - pion system , the statistics in the present work are not sufficient to obtain the scattering phase shift . we therefore used the lellouch - lscher factor for the noninteracting case in the calculation of the @xmath1 process . improving statistics by devising a more efficient operator for the @xmath11 two - pion state is an important work reserved for the future . our calculation is carried out away from the physical quark masses , and the decay of the @xmath16 meson to two zero momentum pions at @xmath3 is considered . clearly , we need to work toward smaller quark masses and a more realistic kinematics in which the two pions carry finite momenta . this will be a major challenge that we now have to face .

, we show that mixings with four - fermion operators with wrong chirality are absent even for the wilson fermion action for the parity odd process in both channels due to cps symmetry . therefore , after subtraction of an effect from the lower dimensional operator , a calculation of the decay amplitudes is possible without complications from operators with wrong chirality , as for the case with chirally symmetric lattice actions . as a first step to verify the possibility of calculations with the wilson fermion action , we consider the decay amplitudes at an unphysical quark mass . for the quark loops in the penguin and disconnected contributions in the channel , the combined hopping parameter expansion and truncated solver method work very well for variance reduction .

we present our result for the decay amplitudes for both the and processes with the improved wilson fermion action . expanding on the earlier works by bernard _ et al . _ and by donini _ et al . _ , we show that mixings with four - fermion operators with wrong chirality are absent even for the wilson fermion action for the parity odd process in both channels due to cps symmetry . therefore , after subtraction of an effect from the lower dimensional operator , a calculation of the decay amplitudes is possible without complications from operators with wrong chirality , as for the case with chirally symmetric lattice actions . as a first step to verify the possibility of calculations with the wilson fermion action , we consider the decay amplitudes at an unphysical quark mass . our calculations are carried out with gauge configurations generated with the iwasaki gauge action and nonperturbatively-improved wilson fermion action at , , and on a ( ) lattice . for the quark loops in the penguin and disconnected contributions in the channel , the combined hopping parameter expansion and truncated solver method work very well for variance reduction . we obtain , for the first time with a wilson - type fermion action , that and for a matching scale . the dependence on the matching scale for these values is weak .

1504.06128

c

we have obtained precision velocities ( to @xmath33 km / s ) and stellar population parameters ( age , metallicity ) for a sample of 77 star clusters in m33 . our principal findings are : * the m33 disc clusters show a clear age - metallicity relation in the sense that younger clusters are more metal - rich than the older clusters . the youngest clusters in our sample have @xmath010 myr ages and near solar metallicities , very similar to the m33 ob star populations . * we find evidence for evolution in the disc metallicity gradient in m33 . the metallicity gradient becomes less negative with time . the evolution in the the metallicity gradient is strong with @xmath60 dex / kpc / gyr . the inner globular clusters ( @xmath6 kpc ) show a steep , negative radial metallicity gradient . * we find little evidence for radial age gradients in the disc clusters . clusters have continued to form throughout the star forming disc ( within 6 kpc ) throughout the disc lifetime . * clusters younger than @xmath4 gyr all exhibit rotation consistent with the disc of m33 . the rotation amplitude decreases and velocity dispersion increases with increasing cluster age . we find a smoothly increasing age - velocity dispersion relation very similar to that seen in the milky way open cluster system . we interpret this as a combination of secular heating processes and cooling of the ism with time . * we identify six new globular cluster candidates that have kinematics and stellar populations consistent with genuine globular clusters . follow - up high resolution imaging is required to unambiguously determine their nature . * we find no strong evidence for a significant age spread in the m33 globular clusters . the majority of globular clusters in our sample are old ( @xmath33 gyr ) . three clusters have spectroscopic ages of @xmath16 gyr . however , one of these is clearly older than this based on the presence of a well - developed blue hb in its @xmath31 cmd ( sarajedini et al . the remaining two clusters may be genuinely intermediate aged clusters in m33 . * the mean metallicity of the m33 globulars is relatively metal - rich ( @xmath38[m / h]@xmath39=@xmath191.12@xmath400.09 ) . this is significantly more metal - rich than the halo gcs in the milky way , and gcs in the lmc and the fornax dsph . based on their high metallicities , spatial distributions , kinematics and structural parameters we argue that the inner gcs are better associated with the m33 disc than halo . we believe that this contribution reinforces the utility of star clusters in studying the disc components of galaxies . since clusters typically span a large range of ages , they can be used to probe disc properties over the whole disc lifetime , while at the same time consistent analysis methods can be applied . this contrasts with complementary approaches that use stellar population tracers that are confined to narrow age ranges ( e.g. ob stars ; urbaneja et al . 2005 ) or age ranges that are not well constrained ( e.g. , pne ; magrini et al . 2004 ; ciardullo et al 2004 ) and require instrinsically different analysis methods . the stellar population analysis used here , consisting of full spectral fitting ( e.g. , koleva et al . 2009 ) to the latest generation of model seds ( vazdekis et al . 2010 ) , is a powerful technique for estimating ages and metallicities of star clusters . however , it does have its limitations . most apparent is its lack of age resolution at old ages . given the uncertainties in stellar population modelling , particularly in understanding non - canonical hot populations and the incorporation of non - solar abundance ratios , our ability to differentiate age amongst the oldest populations is limited . this is most apparent in our discussion of the putative age - spread amongst the m33 globular clusters ( section [ theglobularclusters ] ) . only deep cmds reaching to below the turnoff in these clusters will provide secure ages for these objects . future improvements to this work should include increasing the sample size and spectral range covered for the cluster populations . in particular , going to bluer wavelengths will give additional leverage in constraining the ages of the younger clusters . in addition , providing that the systematics are adequately characterised ( sakari et al . 2014 ) , new techniques that obtain heavy- and light - element abundances via integrated spectroscopy ( e.g. mcwilliam & bernstein 2008 ; colucci et al . 2012 , 2013 ; larsen et al . 2012 ; sakari et al 2013 ) could usefully be applied to m33 star clusters and other nearby disc cluster systems .

we present precision radial velocities and stellar population parameters for 77 star clusters in the local group galaxy m33 . the cluster system exhibits an age - metallicity relation ; the youngest clusters are the most metal - rich . when compared to hi data , clusters with [ m / h] and younger than gyr the clusters show evidence for strong time evolution in the disc radial metallicity gradient ( d[m / h]dt / dr = dex / kpc / gyr ) . the clusters also show a clear age - velocity dispersion relation . the line of sight velocity dispersions of the clusters increases with age similar to milky way open clusters and stars .

we present precision radial velocities and stellar population parameters for 77 star clusters in the local group galaxy m33 . our gtc and wht observations sample both young , massive clusters and known / candidate globular clusters , spanning ages yr , and metallicities , [ m / h ] to solar . the cluster system exhibits an age - metallicity relation ; the youngest clusters are the most metal - rich . when compared to hi data , clusters with [ m / h] and younger than gyr are clearly identified as a disc population . the clusters show evidence for strong time evolution in the disc radial metallicity gradient ( d[m / h]dt / dr = dex / kpc / gyr ) . the oldest clusters have stronger , more negative gradients than the youngest clusters in m33 . the clusters also show a clear age - velocity dispersion relation . the line of sight velocity dispersions of the clusters increases with age similar to milky way open clusters and stars . the general shape of the relation is reproduced by disc heating simulations , and the similarity between the relations in m33 and the milky way suggests that heating by substructure , and cooling of the ism both play a role in shaping this relation . we identify 12 `` classical '' gcs , six of which are newly identified gc candidates . the gcs are more metal - rich than milky way halo clusters , and show weak rotation . the inner ( kpc ) gcs exhibit a steep radial metallicity gradient ( d[m / h]/dr = dex / kpc ) and an exponential - like surface density profile . we argue that these inner gcs are thick disc rather than halo objects . galaxies : local group galaxies : star clusters

astro-ph9906259

c

we have shown the general consequences of a phenomenological two - component @xmath0-process model based on the @xmath1i and @xmath2hf abundances in the early solar system . this model assumes a standard mass of the ism for dilution of the debris from an individual supernova . two scenarios have been investigated to provide bounds on the model . the frequencies of the h ( @xmath67 ) and l ( @xmath66 ) events proposed in the model are constrained by the meteoritic data on @xmath1i and @xmath2hf . the yields in a single h or l event are determined from these meteoritic data and the solar @xmath0-process abundances under the assumption that the yield template in the low ( @xmath4 ) or high ( @xmath3 ) mass region is the same for both the h and l events and follows the corresponding solar @xmath0-pattern in each mass region . these yields are represented by the @xmath189 values for a star formed from an ism contaminated by a single h or l event ( cf . figs . 6 and 7 ) . in this approach , the eu abundance in a single h event is well defined ( cf . fig . 5 ) . with the addition of subsequent supernova @xmath0-process debris to the ism , the abundances from further mixtures of multiple h and l events can be obtained in a straightforward manner . this leads to rather explicit quantitative predictions for stellar abundances in the early galaxy and for the contrast between the stellar abundance pattern at early times and the solar @xmath0-pattern . these predictions may be directly tested by comparison with the observed abundances in the low and high mass regions in very metal - poor stars . it is well known that [ fe / h ] is not a reliable estimator of the galactic age . considering the observed eu abundances , we find that even at very low metallicities of [ fe / h ] @xmath262 , the ism may have already been contaminated by many @xmath0-process events . therefore , we propose that the abundance of eu be the criterion for identifying the earliest stars formed in the galaxy . we predict that those stars with @xmath6 to @xmath7 were formed from an ism contaminated most likely by a single h event within the first @xmath8 yr of the galactic history and should have an ag / eu abundance ratio less than the corresponding solar @xmath0-process value by a factor of at least 10 . the crucial test for these predictions will again be the measurement of abundances in very metal - poor stars . we recognize that measurements at the low eu abundances indicated here may pose very difficult observational problems . in this paper , the fundamental problems of the evolution of supernovae and the sites of the @xmath0-process have not been addressed . our approach has been purely phenomenological . if we assume that the production of all the @xmath0-process nuclei is associated with a proto - typical general supernova event , then a scenario may be suggested that might unify the h and l events ( cf . we consider that a supernova in its earlier stages ejects matter from the proto - neutron star for the @xmath0-process with a relatively high number of neutrons per seed nucleus ( i.e. , a relatively high neutron - to - seed ratio ) . the @xmath0-process then dominantly produces nuclei in the high mass region with relatively few residual nuclei in the low mass region . these events are usually ( i.e. , at a high frequency ) terminated by collapse of the proto - neutron star into a black hole , as may be described by the scenario of brown & bethe ( 1994 ) . on occasion ( i.e. , at a low frequency ) , collapse into a black hole does not occur and the ejection of matter for the @xmath0-process continues but with a lower neutron - to - seed ratio . the @xmath0-process then dominantly produces nuclei in the low mass region with significant yields also for nuclei in the high mass region . the total mass yield of @xmath0-process nuclei in the rare events is much higher due to the longer duration of mass ejection from the stable neutron star . the relative production of black holes to neutron stars in supernovae is @xmath297 to account for the ratio of frequencies for the h and l events . however , the physics that might be responsible for the scenario sketched above remains to be explored . this work is dedicated to david norman schramm and is in the spirit of excitement , hypotheses , and observation that typified his approach . one of us remembers participating in the early wonders of nuclear cosmochronology and the search for extinct nuclei during his thesis . the other remembers the dense presentations and mysteries of earlier nuclear cosmochronologic reports and the interest and excitement of the new studies . the approach used here seeks to follow that of previous scholars . `` the true method of experience first lights the candle ( by hypothesis ) , and then by means of the candle shows the way , commencing as it does with experience duly ordered ... and from it educing axioms ( ` first fruits , ' provisional conclusions ) , and from established axioms again new experiments ... experiment itself shall judge . '' francis bacon , _ novum organum _ ( 1620 ) we greatly appreciate the support by john cowan and christopher sneden in freely providing us information on their work and in maintaining a continued level of interest in testing alternative models , however speculative . discussions with andrew mcwilliam on abundances in very metal - poor stars were of considerable aid . we thank petr vogel for comments on an earlier draft of the paper . this work was supported in part by the us department of energy under contract w-7405-eng-36 and grant de - fg03 - 88er-13851 , and by nasa under grant nag 5 - 4076 , caltech division contribution no . 8641(1032 ) . y .- q. was supported by the j. robert oppenheimer fellowship at los alamos national laboratory .

we present quantitative predictions for the abundances of-process elements in stars formed very early in the galactic history using a phenomenological two - component-process model based on thei andhf inventory in the early solar system . this model assumes that a standard mass of the ism dilutes the debris from an individual supernova . high frequency supernova h events and low frequency supernova l events are proposed in the model with characteristics determined by the meteoritic data oni andhf . the yields in an h or l event are obtained from these characteristics and the solar-process abundances under the assumption that the yield template for the high mass ( ) nuclei associated withw or the low mass ( ) nuclei associated withi is the same for both the h and l events and follows the corresponding solar-pattern in each mass region . we predict that stars with to were formed from an ism contaminated most likely by a single h event within the first yr of the galactic history and should have an ag / eu abundance ratio less than the corresponding solar-process value by a factor of at least 10 . stars formed from an ism contaminated only by a pure l event would have an ag / eu ratio higher than the corresponding solar-process value but would be difficult to find due to the low frequency of the l events .

we present quantitative predictions for the abundances of-process elements in stars formed very early in the galactic history using a phenomenological two - component-process model based on thei andhf inventory in the early solar system . this model assumes that a standard mass of the ism dilutes the debris from an individual supernova . high frequency supernova h events and low frequency supernova l events are proposed in the model with characteristics determined by the meteoritic data oni andhf . the yields in an h or l event are obtained from these characteristics and the solar-process abundances under the assumption that the yield template for the high mass ( ) nuclei associated withw or the low mass ( ) nuclei associated withi is the same for both the h and l events and follows the corresponding solar-pattern in each mass region . this choice of the yield templates is justified by the regular solar - like-process abundance pattern for ba and higher atomic numbers observed in very metal - poor stars . the abundance of eu , not fe , is proposed as a key guide to the age of very metal - poor stars . we predict that stars with to were formed from an ism contaminated most likely by a single h event within the first yr of the galactic history and should have an ag / eu abundance ratio less than the corresponding solar-process value by a factor of at least 10 . many of the very metal - poor stars observed so far are considered here to have been formed from an ism contaminated by many ( )-process events . stars formed from an ism contaminated only by a pure l event would have an ag / eu ratio higher than the corresponding solar-process value but would be difficult to find due to the low frequency of the l events . however , variations in the relative abundances of the low and high mass regions should be detectable in very metal - poor stars .

astro-ph9906335

i

rich clusters of galaxies generally contain a diffuse intracluster medium ( icm ) having temperatures @xmath0 k and densities @xmath1 @xmath2 , as inferred from observations at x - ray and other wavebands ( e.g. , ; ) . an important question related to the overall physics of the icm concerns the central regions of clusters ( @xmath3 kpc ) , where the inferred icm densities and pressures in some cases are sufficiently high that cooling to @xmath4 k can occur on timescales shorter than the cluster lifetime ( e.g. , ; ) . these `` cooling flow '' clusters often exhibit intense optical emission - line nebulae associated with the centrally dominant ( cd ) galaxies at their centers , together with blue continuum excess emission , and the strength of these effects appears to correlate with the cooling rate or central pressure of the x - ray emitting gas (; ; ; ; ; ; , , ; , ; ; ) . the majority of cooling flow cluster cd galaxies are also radio - loud , hosting moderately powerful but relatively compact radio sources @xcite . several intriguing questions have been posed concerning cds in cooling flows . for example , one question concerns the energy source for the line emission : the optical line luminosities are generally one to three orders of magnitude higher than would be expected from the x - ray - derived cooling rates , if each proton in the cooling gas experienced only a single recombination ( e.g. , ; ) . this has led to the consideration of numerous other potential sources of heating , including photoionization by young stars or the agn , auto - ionizing shocks , photoionization by x - rays from the icm , or cosmic - ray heating ( e.g. , and references therein ) . likewise the blue continuum emission is of considerable interest , and suggested possibilities for its origin have included scattered nuclear light , recent star formation , or inverse compton emission . finally , a crucial point to investigate concerns the inter - relationships between these various components : the cd elliptical , the emission - line gas , the blue continuum , the radio source , and the surrounding dense high - pressure icm : how are these related to one another , and do they have underlying common physical relationships ? we present results from a detailed study of a comparatively nearby strong cooling flow cluster , abell 2597 , using images obtained with the wide field and planetary camera 2 ( wfpc2 ) on board the _ hubble space telescope ( hst)_. previous radio and x - ray images have revealed that the cluster contains a moderately luminous radio source ( @xmath5 w hz@xmath6 , ; @xmath7 , ; @xmath8 , ) embedded in a luminous x - ray halo with @xmath9 ergs s@xmath6 (; ; ; ) . the host galaxy of the radio source is a cd elliptical containing an extended , luminous emission - line nebula (; ; ; ) . the galaxy is remarkable for its `` blue lobes '' of continuum excess emission that are approximately co - incident with the radio lobes ( , ) . spatially extended 21-cm absorption has also been detected against the radio lobes . although the radio source is comparatively compact ( with a size @xmath10 kpc ) , its power is comparable to that of much larger fr ii ( `` classical double '' ) sources , suggesting that the dense intracluster medium may play a role in its confinement . the source may be the nearest example of a compact steep - spectrum source . here we present data that fully resolve the blue emission in the lobes and reveal a complex network of emission - line and continuum filaments surrounding the central source . all distance - dependent quantities in this paper have been calculated assuming @xmath11 km s@xmath6 mpc@xmath6 and @xmath12 .

we present results from detailed imaging of the centrally dominant radio elliptical galaxy in the cooling flow cluster abell 2597 , using data obtained with the wide field and planetary camera 2 ( wfpc2 ) on the _ hubble space telescope ( hst)_. this object is one of the archetypal `` blue - lobed '' cooling flow radio elliptical galaxies , also displaying a luminous emission - line nebula , a compact radio source , and a significant dust lane and evidence of molecular gas in its center .

we present results from detailed imaging of the centrally dominant radio elliptical galaxy in the cooling flow cluster abell 2597 , using data obtained with the wide field and planetary camera 2 ( wfpc2 ) on the _ hubble space telescope ( hst)_. this object is one of the archetypal `` blue - lobed '' cooling flow radio elliptical galaxies , also displaying a luminous emission - line nebula , a compact radio source , and a significant dust lane and evidence of molecular gas in its center . we show that the radio source is surrounded by a complex network of emission - line filaments , some of which display a close spatial association with the outer boundary of the radio lobes . we present a detailed analysis of the physical properties of ionized and neutral gas associated with the radio lobes , and show that their properties are strongly suggestive of direct interactions between the radio plasma and ambient gas . we resolve the blue continuum emission into a series of knots and clumps , and present evidence that these are most likely due to regions of recent star formation . we investigate several possible triggering mechanisms for the star formation , including direct interactions with the radio source , filaments condensing from the cooling flow , or the result of an interaction with a gas - rich galaxy , which may also have been responsible for fueling the active nucleus . we propose that the properties of the source are plausibly explained in terms of accretion of gas by the cd during an interaction with a gas - rich galaxy , which combined with the fact that this object is located at the center of a dense , high - pressure icm can account for the high rates of star formation and the strong confinement of the radio source . submitted to _ the astrophysical journal _

astro-ph0102021

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` normal ' galaxies of all morphological types are known to be x - ray emitters , with luminosities in the soft ( @xmath93.5 kev ) x - ray band ranging from @xmath10 to some @xmath11 ergs s@xmath1 ( fabbiano 1989 ) . despite this band being a relatively small part of the electromagnetic spectrum and the x - ray output representing only a small fraction of the bolometric luminosity of a galaxy , x - ray observations are uniquely suited to studying various astrophysical phenomena elusive in other wavelength regimes . whereas the overall emission of a galaxy is dominated by stars in the optical and reprocessed stellar emission in the infrared , x - ray emission is primarily related to the high - energy phenomena associated with end - products of stars : accreting compact objects , supernova remnants , and the shock - heated hot interstellar medium . m81 ( table [ parameters ] ) is an ideal test - bed for our understanding of the x - ray emission components in early - type spirals since it is the nearest such galaxy outside of the local group . it is located in a direction with relatively low galactic absorption ( @xmath12 ; dickey & lockman 1990 ) , considerably lower than that along the line - of - sight to m31 ( @xmath13 ) . compared to the high disk inclination of m31 ( @xmath14 ) , the moderate inclination of m81 ( @xmath15 ) makes its emission components less obscured internally and easier to disentangle spatially . m81 hosts a low - luminosity seyfert nucleus with some characteristics of a low - ionization nuclear emission - line region ( liner ) . the nucleus itself has been studied intensively in many wavelength regimes ( e.g. , ishisaki et al . 1996 ; kaufman et al . 1996 ; ho et al . 1999 and references therein ) . more recently , the outburst of sn 1993j in m81 led to a large number of additional observations , especially in the x - ray band ( e.g. zimmermann et al . 1994a ) . previous observations of m81 resulted in the detection of nine individual x - ray sources including the nucleus , with luminosities in excess of @xmath16 ergs s@xmath1 in the 0.24.0 kev band ( fabbiano 1988 ) . only marginal evidence for variability was found for the nucleus and two other sources . about two - thirds of the non - nuclear emission was not resolved spatially . spectral and temporal properties of the m81 nucleus have been studied , based on both and data ( ishisaki et al . 1996 ; iyomoto & makishima 2000 ; pellegrini et al . 2000 ) . the spectrum of the nuclear source is well described by a power - law with a photon index @xmath17 . in addition , a softer component with a temperature of 0.60.8 kev was also detected . long - term x - ray variability of the m81 nucleus was found , with variations up to a factor of three over a period of 5.5 years , together with intra - day variability of 30% ( iyomoto & makishima 2000 ) . the spectral properties , together with the observed high variability , were regarded as being typical for a low - luminosity agn . the nature of the softer component , however , could not be specified . this paper reports on the results of deep x - ray observations of m81 obtained with the position sensitive proportional counter ( pspc ) and the high resolution imager ( hri ) onboard ( trmper 1983 ) . we focus mainly on the discrete x - ray source population inside the galaxy and the diffuse emission from the disk and the extended bulge of m81 . after a description of the x - ray observations and the data calibration ( [ obs ] ) , we explain the data analysis strategies for the detection of discrete x - ray sources , their variability and the diffuse emission ( [ analysis ] ) . x - ray properties of discrete sources are examined in detail in [ point_sources ] , followed by a discussion of the most interesting sources in a multi - wavelength context in [ multiwavelength ] . results on the diffuse x - ray emission are presented in [ results_diffuse ] . in [ m101 ] , we compare global x - ray properties of m81 and the late - type spiral m101 , for which a similar study has been performed . the results and conclusions are summarized in [ summary ] .

the rest is due to 26 other x - ray sources ( contributing ) and to apparently diffuse emission , which is seen across much of the galactic disk and is particularly bright in the bulge region around the nucleus . the other one is far off the main body of m81 , but is apparently associated with a dense hi concentration produced most likely by the tidal interactions of the galaxy with its companions .

we present results from the analysis of deep hri and pspc observations of the spiral galaxy m81 . the inferred total ( 0.52 kev band ) luminosity of m81 is ergs s , excluding the contribution from identified interlopers found within the ellipse . the nucleus of the galaxy alone accounts for about of this luminosity . the rest is due to 26 other x - ray sources ( contributing ) and to apparently diffuse emission , which is seen across much of the galactic disk and is particularly bright in the bulge region around the nucleus . spectral analysis further gives evidence for a soft component , which can be characterized by a two - temperature optically thin plasma with temperature at kev and 0.60 kev and an absorption of the galactic foreground only . these components , accounting for of the x - ray emission from the region , apparently arise in a combination of hot gas and faint discrete sources . we find interesting spatial coincidences of luminous ( ) and variable x - ray sources with shock - heated optical nebulae . three of them are previously classified as supernova remnant candidates . the other one is far off the main body of m81 , but is apparently associated with a dense hi concentration produced most likely by the tidal interactions of the galaxy with its companions . these associations suggest that such optical nebulae may be powered by outflows from luminous x - ray binaries , which are comparable to , or more luminous than , galactic ` micro - quasars ' .

astro-ph0102021

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we have systematically analyzed pspc and hri observations of the early - type spiral m81 to disentangle different emission components and to derive spatial , spectral and timing characteristics of x - ray sources in the field . the main results and conclusions are as follows : @xmath83 within a region of @xmath36 radius around the m81 nucleus , 69 pspc and 47 hri sources are detected . ten of them are found to be variable . eleven hri and nine additional pspc sources are likely foreground or background objects ( i.e. agn , quasars , galactic stars , etc . ) . excluding these interlopers and the nucleus , 26 x - ray sources are within the @xmath2 ellipse of the galaxy and have luminosities in the range of @xmath126 @xmath127 ergs s@xmath1 in the 0.52 kev band . these sources account for @xmath4 of the total luminosity ( @xmath128 ergs s@xmath1 ) of the galaxy . @xmath83 we find an apparent association of luminous and variable x - ray sources with shock - heated optical nebulae . these sources are in the luminosity range of @xmath7@xmath8 . three position coincidences are with nebulae that are previously classified as snr candidates , and one with a nebula as a superbubble . these associations suggest that such ism structures may be powered by energetic outflows from x - ray binaries . @xmath83 x - ray emission is also detected from holmberg ix , the dwarf companion of m81 . assuming a distance ( 3.6 mpc ) similar to that of m81 , the inferred x - ray luminosity of ho ix is @xmath114 ergs s@xmath1 , which can be easily account for by a number of relatively young snrs and x - ray binaries . @xmath83 we present strong spatial and spectral evidence for the presence of an apparently diffuse x - ray component in m81 . the diffuse x - ray emission is most prominent in the bulge region of the galaxy , although a fraction must arise in faint discrete stellar sources . diffuse x - ray emission fills much of the @xmath2 ellipse of m81 , accounting for @xmath129 ( @xmath130 ergs s@xmath1 ) of the total x - ray luminosity of the galaxy . a significant amount of x - ray emission may be absorbed by cool gas in the spiral arms . nevertheless , the similarity between the radial x - ray and uv intensity profiles and a comparison with m101 suggest that the diffuse x - ray emission is associated with recent massive star activities in m81 . we wish to thank m. yun for providing the hi map used in fig . this research made use of various online services and databases , e.g. ads , heasarc , ned , and ncsa adil as well as the eso science archive facility and the data archive at mpe . the project is supported by nasa under the grants nag 5 - 8999 and nag5 - 9429 . bash , f. n , & kaufman , m. 1996 , , 310 , 621 cruddace , r. g. , hasinger , g. r. , & schmitt , j. h. m. m. 1988 , in eso conf . and workshop proc . 28 , 177 , astronomy from large databases , eds : murtagh , f. , & heck , a. dickey , j. m. , & lockman , f. j. 1990 , , 28 , 215 van dyk , s. d. , weiler , k. w. , sramek , r. a. , et al . 1994 , , 432 , l115 fabbiano , g. 1988 , , 325 , 544 fabbiano , g. 1989 , , 27 , 87 freedman , w. l. , hughes , s. m. , madore , b. f. , et al . 1994 , , 427 , 628 garcia - gomez , c. , & athanassoula , e. 1991 , , 89 , 159 georgiev , t. b. , bilkina , b.i . , tikhonov , n. a. , & karachentsev , i. d. 1991 , , 89 , 529 hasinger , g. , schmidt , m. , & trmper , j. 1991 , , 246 , l2 ho , l. c. , van dyk , s. , pooley , g. g. , sramek , r. a. , & weiler , k. 1999 , , 118 , 843 hopp , u. , et al . 1996 , in iau symposium 171 , 392 , new light on galaxy evolution eds : bender , r. , & davies , r. l. immler , s. , vogler , a. , ehle , m. , & pietsch , w. 1999 , , 352 , 415 irwin , m. , maddox , s. , & mcmahon , r. 1994 , spectrum , 2 , 14 ishisaki , y. , makishima , k. , iyomoto , n. , et al . 1996 , pasj , 48 , 237 iyomoto , n. , & makishima , k. 2000 , , in press ( astro - ph/0010018 ) kaufman , m. , bash , f. n , crane , p. c. , & jacoby , g. 1996 , aj , 112 , 1021 matonick , d. m. , & fesen , r. a. 1997 , , 112 , 49 miller , b. w. , 1995 , 446 , l75 mirabel , i. f. , & rodrguez , l. f. 1994 , , 371 , 46 pellegrini , s. , cappi , m. , bassani , l. , et al . 2000 , , 353 , 447 pietsch , w. , vogler , a. , klein , u. , & zinnecker , h. 2000 , , 360 , 24 snowden , s. l. , & kuntz , k. d. 1998 , cookbook for analysis procedures for xrt observations of extended objects and the diffuse background , part i : individual observations , technical report , nasa / gsfc tennant , a. f. , wu , k. , ghosh , k. k. , et al . 2000 , , submitted ( astro - ph/0012392 ) trmper , j. 1983 , adv . space res . , 2 , 241 de vaucouleurs , g. , de vaucouleurs , a. , corwin , h. g. , et al . 1991 , third reference catalogue of bright galaxies ( springer new york ) voges , w. , gruber , r. , paul , j. , et al . 1992 , in proc . european isy conference , esa isy-3 , 223 , eds : guyenne , t. d. , & hunt , j. j. wang , q. d. 1999 , , 517 , l30 wang , q. d. , immler , s. , & pietsch , w. 1999 , , 523 , 121 yun , m. s. , ho , p. t. p. , & lo , k. y. 1994 , , 372 , 530 zimmermann , h .- u . , lewin , w. , predehl , p. , et al . 1994a , , 367 , 621 zimmermann , h .- u . , becker , w. , belloni , t. , et al . 1994b , exsas user s guide , 4@xmath131 edition , mpe report 257 lrrrrrrrrrr type & sa(s)ab & 1 + & sy1.8/liner & 2 + position of center ( j2000 ) & r.a . @xmath132 & 2 + & dec . @xmath133 & 2 + distance & 3.6 mpc & 3 + & ( @xmath134 kpc ) & + galactic foreground @xmath135 & @xmath136 @xmath45 & 4 + inclination & @xmath137 & 5 + position angle of major axis & @xmath138 & 5 + diameter & @xmath139 & 2 + blue magnitude & 8 mag & 1 lllc hri & 600247h & 1992 oct 23 27 & 26.6 + & 600247h-1 & 1993 apr 17 may 14 & 21.3 + & 600739h & 1994 oct 19 21 & 20.0 + & 600740h & 1995 apr 13 may 4 & 19.2 + & 600881h & 1995 oct 12 25 & 14.9 + & 600882h & 1996 apr 15 may 7 & 18.5 + & 600882h-1 & 1996 oct 27 nov 10 & 5.1 + & 601001h & 1997 mar 29 apr 1 & 19.4 + & 601002h & 1997 sep 30 oct 16 & 19.8 + & 601095h & 1998 mar 25 26 & 12.6 + pspc & 600101p & 1991 mar 25 27 & 9.6 + & 600101p-1 & 1991 oct 16 17 & 11.5 + & 600382p & 1992 sep 29 oct 3 & 28.1 + & 180015p & 1993 apr 3 24 & 18.6 + & 180015p-1 & 1993 may 4 6 & 9.0 + & 180035p & 1993 nov 1 2 & 18.4 + & 180035p-1 & 1993 nov 7 8 & 4.4 + & 180050p & 1994 mar 31 apr 2 & 1.9 lrrrrrrrr h1 & 09 52 41.15 & + 69 02 44.0 & @xmath140 & @xmath141 @xmath142@xmath143 + h2 & 09 53 10.04 & + 69 00 07.6 & @xmath144 & @xmath145 @xmath142@xmath146 + h3 & 09 53 17.01 & + 69 06 46.0 & @xmath147 & @xmath148 @xmath142@xmath149 + h4 & 09 53 49.15 & + 68 52 42.2 & @xmath150 & @xmath151 @xmath142 @xmath152 + h5 & 09 53 51.32 & + 69 02 47.6 & @xmath153 & @xmath154 @xmath142 @xmath155 + h6 & 09 53 57.04 & + 69 03 57.0 & @xmath156 & @xmath157 @xmath142 @xmath155 + h7 & 09 54 16.49 & + 69 16 27.8 & @xmath158 & @xmath159 @xmath142 @xmath160 + h8 & 09 54 45.27 & + 68 57 00.1 & @xmath157 & @xmath158 @xmath142 @xmath161 + h9 & 09 54 50.96 & + 69 02 53.5 & @xmath162 & @xmath163 @xmath142 @xmath164 & var + h10 & 09 55 00.06 & + 69 07 48.4 & @xmath165 & @xmath166 @xmath142 @xmath167 + h11 & 09 55 01.87 & + 68 56 22.1 & @xmath168 & @xmath169 @xmath142 @xmath161 + h12 & 09 55 02.43 & + 68 50 50.9 & @xmath170 & @xmath156 @xmath142 @xmath160 + h13 & 09 55 09.74 & + 69 04 10.1 & @xmath165 & @xmath171 @xmath142 @xmath155 & var + h14 & 09 55 10.27 & + 69 05 04.7 & @xmath172 & @xmath173 @xmath142 @xmath174 + h15 & 09 55 22.04 & + 69 05 14.0 & @xmath175 & @xmath176 @xmath142 @xmath167 + h16 & 09 55 22.03 & + 69 06 41.2 & @xmath162 & @xmath177 @xmath142 @xmath178 + h17 & 09 55 24.37 & + 69 10 02.0 & @xmath148 & @xmath179 @xmath142 @xmath180 & var + h18 & 09 55 24.72 & + 69 01 15.0 & @xmath148 & @xmath181 @xmath142 @xmath182 & var + h19 & 09 55 25.78 & + 69 15 49.8 & @xmath183 & @xmath184 @xmath142 @xmath174 + h20 & 09 55 28.86 & + 69 06 16.1 & @xmath159 & @xmath185 @xmath142 @xmath178 + h21 & 09 55 33.05 & + 69 00 34.9 & @xmath148 & @xmath186 @xmath142 @xmath187 & var + h22 & 09 55 33.32 & + 69 03 57.5 & @xmath148 & @xmath188 @xmath142 @xmath189 & var + h23 & 09 55 35.06 & + 69 03 20.6 & @xmath175 & @xmath190 @xmath142 @xmath160 & + h24 & 09 55 35.08 & + 68 55 15.7 & @xmath153 & @xmath191 @xmath142 @xmath192 + h25 & 09 55 42.13 & + 69 03 39.4 & @xmath165 & @xmath193 @xmath142 @xmath160 & var + h26 & 09 55 43.60 & + 69 17 01.8 & @xmath194 & @xmath195 @xmath142 @xmath160 + h27 & 09 55 43.95 & + 68 59 07.3 & @xmath168 & @xmath163 @xmath142 @xmath164 + h28 & 09 55 47.44 & + 69 05 54.5 & @xmath196 & @xmath165 @xmath142 @xmath192 + h29 & 09 55 49.42 & + 68 58 38.0 & @xmath157 & @xmath145 @xmath142 @xmath155 + h30 & 09 55 49.54 & + 69 08 16.0 & @xmath168 & @xmath197 @xmath142 @xmath164 + h31 & 09 55 50.10 & + 69 05 34.8 & @xmath172 & @xmath198 @xmath142 @xmath199 + h32 & 09 55 58.79 & + 69 05 29.7 & @xmath196 & @xmath200 @xmath142 @xmath164 + h33 & 09 56 02.23 & + 68 59 01.0 & @xmath201 & @xmath184 @xmath142 @xmath192 + h34 & 09 56 02.90 & + 68 59 36.7 & @xmath202 & @xmath203 @xmath142 @xmath164 + h35 & 09 56 09.59 & + 69 12 53.4 & @xmath204 & @xmath205 @xmath142 @xmath167 + h36 & 09 56 09.22 & + 69 01 09.6 & @xmath165 & @xmath176 @xmath142 @xmath167 + h37 & 09 56 13.85 & + 69 06 34.0 & @xmath206 & @xmath207 @xmath142 @xmath164 + h38 & 09 56 14.19 & + 68 57 24.8 & @xmath165 & @xmath208 @xmath142 @xmath174 & var + h39 & 09 56 36.87 & + 69 00 30.1 & @xmath175 & @xmath209 @xmath142 @xmath167 + h40 & 09 57 01.58 & + 68 55 01.3 & @xmath201 & @xmath210 @xmath142 @xmath211 + h41 & 09 57 11.37 & + 69 05 04.1 & @xmath212 & @xmath154 @xmath142 @xmath192 + h42 & 09 57 31.26 & + 69 02 31.9 & @xmath213 & @xmath196 @xmath142 @xmath161 + h43 & 09 57 35.80 & + 69 00 09.1 & @xmath214 & @xmath171 @xmath142 @xmath199 + h44 & 09 57 53.76 & + 69 03 50.3 & @xmath148 & @xmath215 @xmath142 @xmath216 & var + h45 & 09 57 56.44 & + 69 11 39.2 & @xmath217 & @xmath218 @xmath142 @xmath152 + h46 & 09 58 02.94 & + 68 57 10.1 & @xmath219 & @xmath220 @xmath142 @xmath221 + lrrrrrrrrr p1 & 09 52 40.9 & + 69 03 50 & 0.8 @xmath142 0.1 & 0.89 @xmath142 0.28 & 0.73 @xmath142 0.19 & + p2 & 09 52 44.0 & + 69 02 52 & 0.7 @xmath142 0.1 & 1.00 @xmath142 0.36 & 0.62 @xmath142 0.21 & h1 + p3 & 09 52 47.4 & + 69 09 01 & 0.7 @xmath142 0.1 & 1.00 @xmath142 0.36 & 0.39 @xmath142 0.22 & + p4 & 09 52 50.7 & + 68 59 21 & 0.5 @xmath142 0.1 & 0.79 @xmath142 0.41 & 0.06 @xmath142 0.28 & + p5 & 09 53 00.1 & + 69 07 27 & 0.5 @xmath142 0.1 & 0.80 @xmath142 0.36 & 0.56 @xmath142 0.24 & + p6 & 09 53 11.7 & + 68 59 59 & 1.0 @xmath142 0.1 & 1.00 @xmath142 0.21 & 0.18 @xmath142 0.14 & h2 + p7 & 09 53 18.1 & + 69 06 37 & 0.9 @xmath142 0.1 & 0.56 @xmath142 0.14 & 0.42 @xmath142 0.12 & h3 + p8 & 09 53 27.4 & + 69 04 13 & 0.9 @xmath142 0.1 & 1.00 @xmath142 0.18 & 0.55 @xmath142 0.12 & + p9 & 09 53 29.8 & + 68 58 35 & 1.8 @xmath142 0.2 & 0.33 @xmath142 0.08 & 0.23 @xmath142 0.10 & + p10 & 09 53 37.0 & + 69 05 36 & 0.5 @xmath142 0.1 & 0.96 @xmath142 0.35 & 0.27 @xmath142 0.22 & + p11 & 09 53 40.8 & + 68 59 16 & 1.4 @xmath142 0.2 & 0.87 @xmath142 0.12 & 0.59 @xmath142 0.10 & + p12 & 09 53 43.6 & + 69 16 00 & 0.5 @xmath142 0.1 & 1.00 @xmath142 0.53 & 0.51 @xmath142 0.32 & + p13 & 09 53 50.2 & + 68 52 39 & 3.3 @xmath142 0.2 & 0.84 @xmath142 0.06 & 0.42 @xmath142 0.07 & h4 + p14 & 09 53 52.2 & + 69 02 51 & 1.1 @xmath142 0.1 & 1.00 @xmath142 0.15 & 0.35 @xmath142 0.12 & h5 + p15 & 09 53 58.0 & + 69 03 56 & 1.3 @xmath142 0.1 & 0.62 @xmath142 0.12 & 0.28 @xmath142 0.12 & h6 + p16 & 09 54 21.0 & + 69 00 03 & 1.0 @xmath142 0.1 & 0.90 @xmath142 0.14 & 0.47 @xmath142 0.12 & + p17 & 09 54 21.7 & + 68 54 36 & 1.7 @xmath142 0.2 & 0.90 @xmath142 0.13 & 0.23 @xmath142 0.11 & + p18 & 09 54 31.8 & + 68 52 36 & 0.4 @xmath142 0.1 & 0.21 @xmath142 0.24 & 0.45 @xmath142 0.27 & + p19 & 09 54 39.3 & + 69 19 13 & 0.8 @xmath142 0.2 & 1.00 @xmath142 0.29 & 0.09 @xmath142 0.19 & + p20 & 09 54 41.3 & + 69 04 51 & 0.7 @xmath142 0.1 & 0.97 @xmath142 0.25 & 0.26 @xmath142 0.18 & + p21 & 09 54 42.6 & + 69 02 38 & 0.4 @xmath142 0.1 & 0.39 @xmath142 0.24 & 0.46 @xmath142 0.24 & h9 ; var + p22 & 09 54 45.3 & + 68 56 58 & 3.3 @xmath142 0.2 & 0.90 @xmath142 0.05 & 0.10 @xmath142 0.06 & h8 + p23 & 09 54 47.6 & + 69 11 22 & 0.4 @xmath142 0.1 & 1.00 @xmath142 0.43 & 0.19 @xmath142 0.25 & + p24 & 09 55 00.2 & + 69 19 14 & 0.7 @xmath142 0.1 & 0.78 @xmath142 0.30 & 0.11 @xmath142 0.22 & + p25 & 09 55 00.8 & + 69 07 40 & 4.4 @xmath142 0.2 & 0.95 @xmath142 0.04 & 0.51 @xmath142 0.05 & h10 + p26 & 09 55 02.4 & + 69 10 29 & 0.7 @xmath142 0.1 & 1.00 @xmath142 0.26 & 0.37 @xmath142 0.16 & + p27 & 09 55 02.4 & + 68 56 21 & 1.7 @xmath142 0.2 & @xmath222 @xmath142 0.06 & @xmath223 @xmath142 0.10 & h11 + p28 & 09 55 05.5 & + 68 58 53 & 0.3 @xmath142 0.1 & 1.00 @xmath142 0.44 & 0.06 @xmath142 0.28 & + p29 & 09 55 10.5 & + 69 04 04 & 5.1 @xmath142 0.3 & 0.92 @xmath142 0.03 & 0.35 @xmath142 0.05 & h13 ; var + p30 & 09 55 11.0 & + 69 08 29 & 0.6 @xmath142 0.1 & 1.00 @xmath142 0.27 & 0.25 @xmath142 0.19 & + p31 & 09 55 11.0 & + 69 04 60 & 5.6 @xmath142 0.3 & 0.99 @xmath142 0.03 & 0.48 @xmath142 0.04 & h14 + p32 & 09 55 13.6 & + 69 12 32 & 0.4 @xmath142 0.1 & 0.74 @xmath142 0.38 & 0.85 @xmath142 0.27 & + p33 & 09 55 22.7 & + 69 06 31 & 7.3 @xmath142 0.3 & 0.89 @xmath142 0.03 & 0.43 @xmath142 0.04 & + p34 & 09 55 23.7 & + 69 05 08 & 6.1 @xmath142 0.3 & 0.91 @xmath142 0.03 & 0.44 @xmath142 0.04 & h15 + p35 & 09 55 24.6 & + 69 09 54 & 12.3 @xmath142 0.4 & 0.90 @xmath142 0.02 & 0.28 @xmath142 0.03 & h17 ; var + p36 & 09 55 24.9 & + 69 01 13 & 27.0 @xmath142 0.6 & 0.96 @xmath142 0.01 & 0.43 @xmath142 0.02 & h18 ; var + p37 & 09 55 33.1 & + 69 00 34 & 70.1 @xmath142 0.9 & 0.98 @xmath142 0.00 & 0.54 @xmath142 0.01 & h21 ; var + p38 & 09 55 33.6 & + 69 03 54 & 666.5 @xmath142 2.8 & 0.86 @xmath142 0.00 & 0.26 @xmath142 0.00 & h22 ; var + p39 & 09 55 41.0 & + 69 17 21 & 1.1 @xmath142 0.2 & 0.60 @xmath142 0.15 & 0.52 @xmath142 0.13 & h26 + p40 & 09 55 49.2 & + 68 58 41 & 2.2 @xmath142 0.2 & 0.90 @xmath142 0.07 & 0.23 @xmath142 0.08 & + p41 & 09 55 49.4 & + 69 05 32 & 8.1 @xmath142 0.3 & 0.86 @xmath142 0.02 & 0.43 @xmath142 0.04 & h28+h31 + p42 & 09 55 50.0 & + 69 08 09 & 1.5 @xmath142 0.2 & 0.91 @xmath142 0.09 & 0.20 @xmath142 0.09 & h30 + p43 & 09 56 01.5 & + 68 59 09 & 1.8 @xmath142 0.2 & 0.86 @xmath142 0.10 & 0.20 @xmath142 0.10 & h33+h34 + p44 & 09 56 08.9 & + 69 01 07 & 1.5 @xmath142 0.1 & 0.81 @xmath142 0.10 & @xmath224 @xmath142 0.10 & h36 + p45 & 09 56 09.2 & + 69 12 45 & 1.0 @xmath142 0.1 & 1.00 @xmath142 0.17 & 0.18 @xmath142 0.14 & h35 + p46 & 09 56 12.7 & + 69 06 29 & 0.4 @xmath142 0.1 & 1.00 @xmath142 0.37 & 0.35 @xmath142 0.22 & h37 + p47 & 09 56 14.2 & + 68 57 27 & 2.2 @xmath142 0.2 & 0.39 @xmath142 0.07 & 0.07 @xmath142 0.08 & h38 ; var + p48 & 09 56 36.3 & + 69 00 28 & 2.8 @xmath142 0.2 & 0.86 @xmath142 0.06 & 0.31 @xmath142 0.07 & h39 + p49 & 09 56 43.7 & + 68 53 51 & 1.8 @xmath142 0.1 & 0.87 @xmath142 0.12 & 0.54 @xmath142 0.10 & + p50 & 09 56 46.0 & + 68 54 40 & 1.9 @xmath142 0.2 & 1.00 @xmath142 0.10 & 0.58 @xmath142 0.09 & + p51 & 09 56 52.0 & + 69 07 41 & 0.5 @xmath142 0.1 & 0.78 @xmath142 0.26 & 0.36 @xmath142 0.20 & + p52 & 09 56 52.6 & + 69 10 42 & 0.9 @xmath142 0.1 & 0.76 @xmath142 0.16 & 0.09 @xmath142 0.15 & + p53 & 09 56 52.9 & + 69 11 59 & 0.8 @xmath142 0.1 & 1.00 @xmath142 0.20 & 0.49 @xmath142 0.15 & + p54 & 09 56 55.8 & + 69 08 60 & 0.4 @xmath142 0.1 & 0.78 @xmath142 0.33 & 0.47 @xmath142 0.23 & + p55 & 09 57 01.4 & + 68 54 60 & 4.4 @xmath142 0.3 & 0.88 @xmath142 0.04 & 0.12 @xmath142 0.06 & h40 + p56 & 09 57 01.6 & + 68 56 49 & 0.6 @xmath142 0.1 & 0.93 @xmath142 0.32 & 0.14 @xmath142 0.23 & + p57 & 09 57 10.9 & + 69 05 01 & 0.6 @xmath142 0.1 & 1.00 @xmath142 0.27 & 0.13 @xmath142 0.20 & h41 + p58 & 09 57 14.4 & + 69 11 35 & 0.5 @xmath142 0.1 & 0.94 @xmath142 0.29 & 0.21 @xmath142 0.21 & + p59 & 09 57 17.2 & + 69 10 12 & 0.5 @xmath142 0.1 & 0.94 @xmath142 0.30 & 0.48 @xmath142 0.21 & + p60 & 09 57 17.5 & + 68 58 27 & 1.4 @xmath142 0.2 & 0.95 @xmath142 0.12 & 0.33 @xmath142 0.11 & + p61 & 09 57 26.9 & + 68 53 16 & 0.6 @xmath142 0.1 & 1.00 @xmath142 0.41 & 0.08 @xmath142 0.25 & + p62 & 09 57 28.4 & + 69 13 30 & 1.8 @xmath142 0.2 & 0.99 @xmath142 0.11 & 0.25 @xmath142 0.10 & + p63 & 09 57 29.8 & + 69 02 32 & 0.8 @xmath142 0.1 & 0.80 @xmath142 0.18 & 0.02 @xmath142 0.16 & h42 + p64 & 09 57 35.6 & + 69 00 09 & 1.6 @xmath142 0.2 & 1.00 @xmath142 0.11 & 0.11 @xmath142 0.10 & h43 + p65 & 09 57 35.7 & + 69 16 07 & 0.7 @xmath142 0.2 & 0.98 @xmath142 0.27 & 0.37 @xmath142 0.18 & + p66 & 09 57 53.3 & + 69 03 48 & 198.0 @xmath142 1.6 & 0.97 @xmath142 0.00 & 0.39 @xmath142 0.01 & h44 ; var + p67 & 09 57 55.7 & + 69 11 33 & 3.1 @xmath142 0.2 & 0.84 @xmath142 0.07 & 0.22 @xmath142 0.07 & h45 + p68 & 09 57 57.3 & + 69 06 11 & 0.9 @xmath142 0.2 & 0.70 @xmath142 0.21 & 0.24 @xmath142 0.20 & + p69 & 09 58 02.2 & + 68 57 10 & 3.7 @xmath142 0.3 & 0.16 @xmath142 0.05 & 0.03 @xmath142 0.07 & h46 + lrrrrrrr h2 = p6 & 6.0 & 11.82 & 14.13 & 2.31 & gs 0438301079 ; u1575 03021793 + h3 = p7 & 5.4 & 18.0 & 19.40 & @xmath225 & u1575 03022008 + p9 & 12.0 & 11.02 & 12.47 & 1.72 & gs 0438300727 ; u1575 03022347 + p11 & 6.9 & 19.27 & & @xmath226 & non - stellar + h4 = p13 & 3.6 & 19.06 & 20.69 & 1.63 & u1575 03022935 + p14 & 12.6 & 18.17 & 21.18 & 3.01 & non - stellar + h6 = p15 & 4.2 & 19.77 & & @xmath227 & stellar + p19 & 3.1 & 19.81 & & @xmath228 & u1575 03024392 + h8 = p22 & 1.8 & 12.45 & 13.55 & 1.10 & gs 0438300613 ; u1575 03024587 + h9 & 5.0 & & & & snr mf4 + p23 & 7.4 & 18.90 & 19.50 & 0.60 & u1575 03024612 + h11 = p27 & 5.9 & 10.31 & 11.62 & 1.31 & gs 0438301127 ; u1575 03025086 + h13 = p29 & 4.5 & & & & x2 ; snr mf11 + h14 = p31 & 2.9 & & & & x3 + h17 = p35 & 6.3 & & & & x4 + h18 = p36 & 1.3 & & & & sn 1993j + h21 = p37 & 2.7 & & & & x6 ; snr mf22 + h22 = p38 & 3.3 & & & & x5 ; m81 nucleus + h31 & 5.2 & & & & x7 + h38 = p47 & 0.5 & 16.85 & 19.37 & 2.52 & x8 ; u1575 03027313 + h39 = p48 & 2.3 & 17.07 & 17.24 & 0.17 & u1575 03027973 + p49 & 15.3 & 14.72 & 15.93 & 1.21 & gs 0438300776 ; u1575 03028257 + h40 = p55 & 0.7 & 16.91 & 17.37 & 0.46 & u1575 03028660 + p56 & 5.0 & 18.71 & 20.48 & 1.87 & u1575 03028666 + p58 & 8.0 & 14.84 & 16.09 & 1.25 & gs 0438300612 + p62 & 10.6 & 18.51 & & @xmath229 & non - stellar + h42 = p63 & 3.1 & & 19.92 & @xmath230 & ho ix + h44 = p66 & 4.3 & 17.80 & & @xmath231 & x9 ; u1575 03030069 ; nebula + h45 = p67 & 8.5 & 19.44 & 21.17 & 1.73 & non - stellar + h46 = p69 & 2.4 & 9.95 & 11.51 & 1.56 & gs 0438301132 + lrrcrccccr mf4 & @xmath232 & @xmath233 & 6.2 & @xmath234 & 0.58 & 40 & stellar & h9 & @xmath235 + mf11 & @xmath236 & @xmath237 & 4.5 & @xmath238 & 1.58 & 40 & stellar & h13/p29 & @xmath239 + mf22 & @xmath240 & @xmath241 & 2.7 & @xmath242 & 0.85 & 90 & filled & h21/p37 & @xmath127 + lccc total galaxy & 0.457 & 2.83 & 100 + point - like nuclear source ( h22 ) & 0.295 & 1.83 & 65 + interlopers ( h11 , h39 , h40 , h41 ) & 0.005 & 0.03 & 1 + point sources & 0.044 & 0.27 & 10 + diffuse emission within the @xmath2 ellipse & 0.113 & 0.70 & 24 + total bulge emission ( @xmath122 radius ) & 0.354 & 2.19 & 100 + point - like nuclear source ( @xmath122 radius ) & 0.292 & 1.81 & 83 + extended bulge emission ( @xmath122 radius ) & 0.062 & 0.38 & 17 + lccc + @xmath83 thermal plasma 1 & 0.15 ( 0.130.17 ) & 4.8 ( 4.74.9 ) & @xmath243 + @xmath83 thermal plasma 2 & 0.63 ( 0.520.74 ) & 6.0 ( 5.76.3 ) & @xmath244 + @xmath83 power law & 1.85 ( 1.831.87 ) & 23 ( 2225 ) & @xmath245 +

the nucleus of the galaxy alone accounts for about of this luminosity . we find interesting spatial coincidences of luminous ( ) and variable x - ray sources with shock - heated optical nebulae . three of them are previously classified as supernova remnant candidates . these associations suggest that such optical nebulae may be powered by outflows from luminous x - ray binaries , which are comparable to , or more luminous than , galactic ` micro - quasars ' .

we present results from the analysis of deep hri and pspc observations of the spiral galaxy m81 . the inferred total ( 0.52 kev band ) luminosity of m81 is ergs s , excluding the contribution from identified interlopers found within the ellipse . the nucleus of the galaxy alone accounts for about of this luminosity . the rest is due to 26 other x - ray sources ( contributing ) and to apparently diffuse emission , which is seen across much of the galactic disk and is particularly bright in the bulge region around the nucleus . spectral analysis further gives evidence for a soft component , which can be characterized by a two - temperature optically thin plasma with temperature at kev and 0.60 kev and an absorption of the galactic foreground only . these components , accounting for of the x - ray emission from the region , apparently arise in a combination of hot gas and faint discrete sources . we find interesting spatial coincidences of luminous ( ) and variable x - ray sources with shock - heated optical nebulae . three of them are previously classified as supernova remnant candidates . the other one is far off the main body of m81 , but is apparently associated with a dense hi concentration produced most likely by the tidal interactions of the galaxy with its companions . these associations suggest that such optical nebulae may be powered by outflows from luminous x - ray binaries , which are comparable to , or more luminous than , galactic ` micro - quasars ' .

astro-ph0609356

r

in our search for planetary companions we come to the same result as @xcite of no faint companion candidates around g172 - 1 . however , we were easily able to resolve this @xmath388 binary for the first time into two almost equal - magnitude components . this binary was first observed by @xcite in 1999 as part of a triple system with a very wide b component with @xmath389 separation to the primary . this corresponds to a separation of @xmath390 when using our distance estimate of @xmath391 . we were not able to image the wide component due to our limited field of view of @xmath121 . g39 - 29 was discovered to be a binary by @xcite . interestingly , there seems to be significant observable dynamics to the system since their measurement of @xmath392 in september 2002 differs strongly from our @xmath393 in october 2005 , which corresponds to a tangential motion in the plane of the sky of @xmath394 relative to the primary . at the same time the position angle stayed approximately the same ( @xmath395 in 2002 , @xmath396 in 2005 ) . we therefore conclude that the system is probably highly inclined . further observations will be needed to set constraints on orbital elements . we are the first to resolve this 0.53 arcsecond binary . a recent distance estimate by @xcite using low resolution spectroscopy resulted in a value of @xmath397 for the unresolved object . our value of @xmath398 agrees with that value on the @xmath399-level , taking the newly discovered binarity into account by multiplying the @xcite - result by a factor of @xmath317 . the binarity of this highly interesting variable object with the alternative identifier v372pup was discovered by @xcite . unfortunately , separation and position angle are not published , which would have allowed further analysis of this close @xmath400 projected separation ( this paper ) binary . a trigonometric parallax was measured by the _ hipparcos _ satellite @xcite . its value of @xmath401 corresponding to a distance of @xmath402 is in excellent agreement with our value of @xmath403 . this object ( subsequently 2m1036 ) is found to be a triple system . it shows a @xmath404 , k@xmath405 primary component accompanied by a pair of equal magnitude ( @xmath406 , k@xmath407 ) objects at @xmath408 , which themselves are separated by @xmath409 ( see figure [ fig5 ] ) . with a distance of @xmath410 , this high proper motion system was calculated to have the second - largest distance of all objects in our sample . its binary nature is reported here for the first time . this binary ( hereafter 2m1334 ) was discovered with a separation of @xmath411 , just at the resolution limit of this survey of @xmath412 . after its binarity was first published by @xcite , the primary was discussed by @xcite as hosting either an 11,000k white dwarf or an m6 companion . from our observed @xmath413 and @xmath414 for the companion we can exclude the possibility of a white dwarf companion , since we would expect @xmath127 to be less than zero for a predicted 11,000k white dwarf according to models of @xcite . we therefore conclude the companion to be a late type main sequence star . our spectral type estimations yield a value of m@xmath415 for the secondary , which is therefore the latest type companion in this sample . the inferred mass of the secondary is possibly below the hydrogen burning limit ( @xmath416 ) , which makes this object a brown dwarf candidate . this is also the lowest mass companion found in this survey . @xcite found a photometric distance of @xmath417 for the unresolved binary . this is in good agreement with our value of @xmath418 when multiplying with a factor of @xmath419 to account for the binarity discovered by our survey . the binary nature of this @xmath420 separated slow - moving system was first found by @xcite . we were able to clearly resolve the components of this newly discovered tight @xmath421 binary . our observations are the first to identify this system as a binary , with separation 1.9 arcseconds . the optical spectrum @xcite shows strong balmer emission , consistent with the young age inferred from the strong x - ray flux . our observations reveal a number of faint sources near the targeted stars that we have rejected as potential companions . here , we outline the rational behind those decisions for a selection of objects . a very faint @xmath422 and @xmath423 point - like object was found at a position angle of @xmath424 at a distance of @xmath425 to the primary ( see figure [ fig10 ] ) . follow - up observations with the gemini north telescope were conducted 2 months after first detection to test for proper motion correlation of the primary and companion candidate . from the two epoch data a relative motion of the central object and companion was derived and compared with the known proper motion of @xmath426 of the primary . we find that the data are consistent with a distant background object . and @xmath427 companion to g173 - 39 was detected with a separation of @xmath428 to the central star . assuming that this object resides in the same distance as g173 - 39 ( 14.3au ; gliese & jahrei 1991 ) , this corresponds to a @xmath429 companion in 53.3au separation to the central object at an age of 500myr . follow - up observations revealed its background nature through proper motion arguments . [ fig10 ] ] we detected a companion to lp390 - 16 at only @xmath430 separation with a delta magnitude of more than 7mag in h and k band . combining proper motion with point source locations in old exposures from possi , however , we find the object to be consistent with a non - moving object , and therefore conclude it to be a background star . follow - up observations helped to reject 7 companion candidates at separations between @xmath431 and @xmath432 to g125 - 15 . after a first observation in june 2005 the central object moved @xmath433 due to proper motion until a second observation in april 2006 . this corresponds to @xmath434 on the detector , which exposes the fixed companion candidates to be distant background stars . in @xmath435 separation to the central object we detected two faint objects with a separation of @xmath436 . the proper motion of lp756 - 3 ( 0.353 arcsec / yr ) and second epoch data 10 months after our first observation were used to reveal their background nature . four of the 13 observed multiples already have published separations and position angles ; proper motions are known for all . comparing our data taken in 2005 with the earlier epoch data of the other groups we find that all four binaries are consistent with physically related companions . evidence for the physical nature of the other multiples is given by proper motion arguments . our sample consists of relatively nearby m stars that show significant proper motions . looking at multiple epoch data , a background star mimicking a bound companion would remain fixed while the foreground object would move by . as the @xmath123 of all observed binaries range from @xmath437 to @xmath438 only ( implying apparent magnitudes of @xmath439 ) , these bright companions would show up in possi data taken at much earlier epoch . no bright background objects were found in the vicinity of any of the estimated secondary locations leading to the conclusion that these cool companions are physically bound to their primaries .

we find that the separation distribution of the binaries in this sample peaks at , which is consistent with previous measurements of early - m binaries . hence , early - m binaries seem to occur in on average tighter systems than g binaries . at the same time

we present results of a high - resolution , near - infrared survey of 41 nearby , young ( ) m0m5.0 dwarfs using the altair natural guide star adaptive optics system at the gemini north telescope . twelve of the objects appear to be binaries , 7 of which are reported here for the first time . one triple system was discovered . statistical properties are studied and compared with earlier ( f to k ) and later ( m6 very low - mass , vlm ) populations . we find that the separation distribution of the binaries in this sample peaks at , which is consistent with previous measurements of early - m binaries . hence , early - m binaries seem to occur in on average tighter systems than g binaries . at the same time they are significantly wider than field vlm binary stars . the distribution of mass ratios of primary and secondary stars was found to show an intermediate distribution between the strongly peaked distribution of field vlm systems and the almost flat distribution of earlier - type stars . consequently , we show evidence for relatively young , early - m binaries representing a transition between the well known earlier star distributions and the recently examined field vlm population characteristics . despite the fact that this survey was dedicated to the search for faint brown dwarf and planetary mass companions , all planetary mass candidates were background objects . we exclude the existence of physical companions with masses greater than 10 jupiter masses ( ) at separations of and masses greater than for separations around 37 of the 41 observed objects .

astro-ph0609356

c

observations of binaries and their inherent parameters are important for setting constraints on the formation mechanism of stars in general . this sample of young , early - m dwarfs allows insight into a population of stars in between the well - known g and k star population and the distinctly different vlm population @xcite , which became analyzable only a few years ago with the development and employment of highly sensitive ao and the _ hst _ ( close et al . 2003 ; gizis et al . 2003 ; bouy et al . 2003 ) . we found 12 binaries and 1 triple system in our sample of 41 objects . in order to derive a multiple star fraction free of malmquist bias , we consider only the systems in our sample whose distances are within 20pc . eight of the observed multiples are likely within 20pc of the sun , as are estimatedly all of the observed single stars . however , the distances of two of the 8 objects ( g172 - 1 , 2m1036 ) are within @xmath440 of the 20pc limit , leaving a rather large probability that they are not part of the defined volume . likewise , two binaries have estimated distances @xmath441 greater than 20pc ( lp717 - 36 and lp642 - 48 ) , so they may be part of the limited sample . this therefore leaves @xmath442 confirmed binaries within 20pc . to eliminate uncertainties caused by the distance dependence of the sensitivity , we conservatively cut the sample at a mass ratio of @xmath443 . there are 28 objects in this sub - sample other than the confirmed binaries . four of these have candidate companions with @xmath444 . hence , we include them in this binary fraction as single stars . in addition , we include one possible binary system in the upper limit estimate . this results in a total of @xmath445 multiples in a sample of @xmath446 objects ( upper and lower limits correspond to each other , respectively ) , resulting in a nominal binary fraction of @xmath447 for @xmath448 and @xmath449au ( we use binomial statistics to estimate the uncertainty as described in @xcite ) . the cut in separation is determined by the minimum resolution of @xmath450 at the distance limit of 20pc . we note , however , that this above examination of the binary fraction does not account for selection effects in the sample selection . figure [ fig11 ] shows the mass ratio @xmath451 distribution derived from the 13 observed multiples using the masses listed in table [ tab3 ] . the triple system 2m1036 is accounted for as two binaries , the binary bc and the a(bc ) system . mass ratios for these two objects are therefore @xmath452 and @xmath453 . in the following paragraphs we sometimes refer to 14 `` binaries '' , but one should keep in mind that this means 12 binaries and 1 triple system . twelve out of the 14 have mass ratios of @xmath454 ; we regard this as evidence that equal - mass systems are preferred for young , early - m dwarf primaries . our observations are sensitive to binaries with mass ratios @xmath444 for separations greater than @xmath455 ( see figure [ fig12 ] ) . observations have shown that there is a significant lack of very low - mass objects around main sequence stars for separations smaller than 5 au ( the `` brown dwarf desert '' ; marcy & butler 2000 ) . we therefore do not expect to have missed a large quantity of objects . however , we have to assume that for @xmath444 the sample is likely incomplete . the continuous line shows the distribution derived from the 14 early - m binaries in this paper ( triple 2m1036 included as two binaries , see [ massratio ] ) . the dashed line shows the distribution of binaries included in an early f to k star sample by @xcite that have separations @xmath456 . the dotted line shows the @xmath3 distribution for vlm stars from @xcite . while the f to k binary distribution is described by a rather flat distribution , slightly more populated at higher @xmath3 , the vlm distribution shows a significant peak for equal mass binaries . the early - m binary distribution with its broad peak at @xmath457 might represent an intermediate distribution between the earlier and later types . due to the high sensitivity of our measurements , only the last , @xmath444 bin is significantly affected by incompleteness . [ fig11 ] ] as a function of projected binary separation in astronomical units for the 12 discovered binaries ( filled circles ) . the triple 2m1036 is included as the two binaries a(bc ) and bc ( squares ; for further explanation see [ massratio ] ) . the dashed line represents the sensitivity limit of our survey , derived from the sensitivity relation shown in figure [ fig3 ] and 500myr models from @xcite . as a demonstration of detection capabilities , the open circle at @xmath458 and @xmath459 is the companion seen in figure [ fig10 ] if it were a physical companion to g173 - 39 . [ fig12 ] ] this emphasis on @xmath460 is not seen in the distributions of earlier type stars . @xcite show that for late f to k binaries with separations of less than 100au the distribution of mass ratios is rather flat with only marginal tendency towards equal mass binaries . for field vlm binaries , however , the opposite effect is observed ; recent statistical evaluations of all currently known vlm binaries @xcite show a significant peak at @xmath461 . it is therefore possible that the mass ratio distribution of our early - m binaries sample has an intermediate distribution between the flat f - k distribution and the strongly peaked field vlm distribution . however , our sample of binaries is rather small . further observations of a larger number of young m stars will be needed to show if this relation holds . mass ratios @xmath462 as a function of binary separation are shown in figure [ fig12 ] . while at separations @xmath463au systems are distributed over a broad range of mass ratios , all three binaries with separations @xmath464au show mass ratios of @xmath465 . the sensitivity of the observations would have allowed for the detection of much lower mass ratios at these separations ( see figure [ fig10 ] for example ) , indicating a real lack of objects with low mass ratios and high separations . however , a sample of 14 binaries can not fill the accessible space in the @xmath466 plane uniformly , limiting the significance of this result due to low number statistics . figure [ fig13 ] shows the separation distribution of our set of 14 binaries . the physical projected separations range from 2.2 to 49.7au and possess a distribution that shows no significant peak . however , since the observations cover separations up to 15 arcseconds , which corresponds to 300au at a distance of 20pc , we conclude that the decreasing number of detected objects for separations higher than @xmath467au is a real effect . the underlying distribution therefore probably peaks within 0 to 50au . a least-@xmath468 fit of a poisson distribution to the data suggests a peak at @xmath2 . this is consistent with earlier results , for instance by @xcite , who report a broad peak at @xmath469@xmath470 for m2m4.5 binaries . bin is probably incomplete due to the finite resolution of @xmath48 corresponding to 1.6au in 20pc . [ fig13 ] ] the separation distribution , again , shows evidence that young , early - m binaries possess transitional characteristics between earlier and later type populations . with a distribution peaking at @xmath471 @xcite , g stars seem to have on average greater separations than early - m stars . field vlm binaries , however , are preferably found in significantly tighter systems . the distribution of 70 binaries with spectral types later than m5.5 shows a significant peak at @xmath472@xmath473 @xcite with a steep quantitative decrease of systems with higher separations . g k binaries are described by a mass ratio distribution and a separation distribution that are very different from the vlm binaries characteristics ; young , early - m binaries appear to show an intermediate behavior . the higher and the lower mass distributions are apparently connected through a smooth transition embodied by early - m binaries .

the distribution of mass ratios of primary and secondary stars was found to show an intermediate distribution between the strongly peaked distribution of field vlm systems and the almost flat distribution of earlier - type stars . consequently , we show evidence for relatively young , early - m binaries representing a transition between the well known earlier star distributions and the recently examined field vlm population characteristics . despite the fact that this survey was dedicated to the search for faint brown dwarf and planetary mass companions , all planetary mass candidates were background objects .

we present results of a high - resolution , near - infrared survey of 41 nearby , young ( ) m0m5.0 dwarfs using the altair natural guide star adaptive optics system at the gemini north telescope . twelve of the objects appear to be binaries , 7 of which are reported here for the first time . one triple system was discovered . statistical properties are studied and compared with earlier ( f to k ) and later ( m6 very low - mass , vlm ) populations . we find that the separation distribution of the binaries in this sample peaks at , which is consistent with previous measurements of early - m binaries . hence , early - m binaries seem to occur in on average tighter systems than g binaries . at the same time they are significantly wider than field vlm binary stars . the distribution of mass ratios of primary and secondary stars was found to show an intermediate distribution between the strongly peaked distribution of field vlm systems and the almost flat distribution of earlier - type stars . consequently , we show evidence for relatively young , early - m binaries representing a transition between the well known earlier star distributions and the recently examined field vlm population characteristics . despite the fact that this survey was dedicated to the search for faint brown dwarf and planetary mass companions , all planetary mass candidates were background objects . we exclude the existence of physical companions with masses greater than 10 jupiter masses ( ) at separations of and masses greater than for separations around 37 of the 41 observed objects .

astro-ph0609356

i

we have conducted a survey of 41 nearby , early - m stars of ages comparable to the pleiades cluster , searching for companions down to planetary masses using the gemini north telescope with its ao system altair . thirteen stars were observed to host fairly bright companions , 8 of these multiples ( 7 binaries , 1 triple ) are new discoveries . we derived physical parameters for each of the multiple components allowing for further analysis of the early - m star population confirming existing statistical results and contributing additional empirical constraints on star and binary formation . the binary fraction of this sample of young , early - m stars was found to be @xmath447 for mass ratios @xmath448 and @xmath449au . however , a full analysis of systematic errors and biases could not be made , this value might therefore differ significantly from the actual value for this group of stars . the mass ratio distribution was analyzed and compared with distributions drawn from f k stars and from vlm stars . the young , early - m binary data was shown to be best described as an intermediate distribution between the almost flat early type star distribution and the strongly @xmath474 peaked field vlm distribution , however , our sample size is relatively small . the most likely separation was found to be @xmath2 , which is less than the median value of the g binary distribution . field vlm binaries , however , tend to be bound in significantly tighter systems . we conclude that early - m binaries possess characteristics filling the gap between the very distinct field vlm population and stars earlier than m. a sensitivity estimate to the detection of planetary mass companions was made using planetary evolution models . since we found no faint physical companions around 37 of the observed sources we can exclude conservatively assuming an age of 500myr companions more massive than 10m@xmath475 at separations of @xmath383 and heavier than @xmath476 at separations of @xmath382 around all these objects . we thank the anonymous referee for many valuable comments leading to an improved paper . the authors are grateful to jean - ren roy , deputy director & head of science at gemini north , for kindly allocating special ddt time for follow - up observations . this work is based on observations obtained at the gemini observatory , which is operated by the association of universities for research in astronomy , inc . , under a cooperative agreement with the nsf on behalf of the gemini partnership : the national science foundation ( united states ) , the particle physics and astronomy research council ( united kingdom ) , the national research council ( canada ) , conicyt ( chile ) , the australian research council ( australia ) , cnpq ( brazil ) and conicet ( argentina ) . program ids of the gemini observations are gn-2005a - q-28 , gn-2005b - q-14 , and gn-2006a - q-83 . this publication makes use of data products from the two micron all sky survey , which is a joint project of the university of massachusetts and the infrared processing and analysis center / california institute of technology , funded by the national aeronautics and space administration and the national science foundation . this research has made use of the simbad database , operated at cds , strasbourg , france . the national geographic society - palomar observatory sky atlas ( poss - i ) was made by the california institute of technology with grants from the national geographic society . lmc is supported by an nsf career award and the nasa origins of solar systems program . allen , p. r. , koerner , d. w. , reid , i. n. , & trilling , d. e. 2005 , , 625 , 385 baraffe , i. , chabrier , g. , allard , f. , & hauschildt , p. h. 1998 , , 337 , 403 baraffe , i. , chabrier , g. , barman , t. s. , allard , f. , & hauschildt , p. h. 2003 , , 402 , 701 becklin , e. e. , & zuckerman , b. 1988 , , 336 , 656 beers , t. c. , rossi , s. , ulrich , d. , & wilhelm , r. 1996 , , 112 , 1188 bergeron , p. , wesemael , f. , & beauchamp , a. 1995 , , 107 , 1047 beuzit , j .- l . , et al . 2004 , , 425 , 997 bouy , h. , brandner , w. , martn , e. l. , delfosse , x. , allard , f. , & basri , g. 2003 , , 126 , 1526 burgasser , a. j. , kirkpatrick , j. d. , reid , i. n. , brown , m. e. , miskey , c. l. , gizis , j. e. 2003 , , 586 , 512 burgasser , a. j. , reid , i. n. , siegler , n. , close , l. , allen , p. a. , lowrance , p. , gizis , j. e. 2006 , in _ protostars & planets v _ b. reipurth , u. arizona press burrows , a. , hubbard , w.b . , lunine , j.i . , liebert , j. 2001 , rev . phys . , 73 , 719 close , l. m. , potter , d. , brandner , w. , lloyd - hart , m. , liebert , j. , burrows , a. , & siegler , n. 2002 , , 566 , 1095 close , l. m. , siegler , n. , freed , m. , & biller , b. 2003 , , 587 , 407 close , l. m. et al . 2006 , , submitted cruz , k. l. , & reid , i. n. 2002 , , 123 , 2828 cruz , k. l. , reid , i. n. , liebert , j. , kirkpatrick , j. d. , & lowrance , p. j. 2003 , , 126 , 2421 delfosse , x. , forveille , t. , sgransan , d. , beuzit , j .- l . , udry , s. , perrier , c. , & mayor , m. 2000 , , 364 , 217 duquennoy , a. , & mayor , m. 1991 , , 248 , 485 fischer , d.a . & marcy , g. w. 1992 , , 396 , 178 gizis , j. e. , reid , i. n. , knapp , g. r. , liebert , j. , kirkpatrick , j. d. , koerner , d. w. , & burgasser , a. j. 2003 , , 125 , 3302 gliese , w. , & jahrei , h. 1991 , on : the astronomical data center cd - rom : selected astronomical catalogs , vol . i ; l.e . brotzmann , s.e . gesser ( eds . ) , nasa / astronomical data center , goddard space flight center , greenbelt , md golimowski , d. a. , et al . 2004 , , 128 , 1733 gould , a. , & chanam , j. 2004 , , 150 , 455 hawley , s. l. , gizis , j. e. , & reid , i. n. 1996 , , 112 , 2799 hodapp , k. w. , et al . 2003 , , 115 , 1388 hnsch , m. , schmitt , j. h. m. m. , sterzik , m. f. , & voges , w. 1999 , , 135 , 319 jao , w .- c . , henry , t. j. , subasavage , j. p. , bean , j. l. , costa , e. , ianna , p. a. , & mndez , r. a. 2003 , , 125 , 332 jones , b. f. , fischer , d. a. , & stauffer , j. r. 1996 , , 112 , 1562 kirkpatrick , j. 1996 , hst proposal , 2795 kirkpatrick , j. d. , dahn , c. c. , monet , d. g. , reid , i. n. , gizis , j. e. , liebert , j. , & burgasser , a. j. 2001 , , 121 , 3235 luyten , w. 1980 , nltt catalogue ( minneapolis , university of minnesota ) marcy , g. w. , & butler , r. p. 2000 , , 112 , 137 mccarthy , c. , zuckerman , b. , & becklin , e. e. 2001 , , 121 , 3259 martn , e. l. , barrado y navascus , d. , baraffe , i. , bouy , h. , & dahm , s. 2003 , , 594 , 525 micela , g. , sciortino , s. , harnden , f. r. , kashyap , v. , prosser , c. f. , damiani , f. , stauffer , j. , caillault , j .- p . 1999 , , 341 , 751 nakajima , t. , oppenheimer , b. r. , kulkarni , s. r. , golimowski , d. a. , matthews , k. , & durrance , s. t. 1995 , , 378 , 463 oppenheimer , b. r. , golimowski , d. a. , kulkarni , s. r. , matthews , k. , nakajima , t. , creech - eakman , m. , & durrance , s. t. 2001 , , 121 , 2189 perryman , m. a. c. , & esa 1997 , the hipparcos and tycho catalogues . astrometric and photometric star catalogues derived from the esa hipparcos space astrometry mission , publisher : noordwijk , netherlands : esa publications division , 1997 , series : esa sp series vol no : 1200 , isbn : 9290923997 ( set ) reid , n. 2003 , , 342 , 837 reid , i. n. , gizis , j. e. , & hawley , s. l. 2002 , , 124 , 2721 reid , i. n. , gizis , j. e. , kirkpatrick , j. d. , & koerner , d. w. 2001 , , 121 , 489 reid , i. n. , hawley , s. l. , & gizis , j. e. 1995a , , 110 , 1838 reid , i. n. , hawley , s. l. , mateo , m. 1995b , , 272 , 828 reid , i. n. , et al . 2003 , , 126 , 3007 reid , i. n. , et al . 2004 , , 128 , 463 riaz , b. , gizis , j. e. , & harvin , j. 2006 , , 132 , 866 siegler , n. , close , l. m. , cruz , k. l. , martn , e. l. , & reid , i. n. 2005 , , 621 , 1023 scholz , r .- d . , meusinger , h. , & jahreiss , h. 2005 , vizier online data catalog , 344 , 20211 simons , d. a. , henry , t. j. , & kirkpatrick , j. d. 1996 , , 112 , 2238 van biesbroeck , g. 1944 , , 51 , 61 voges , w. , et al . 1999 , , 349 , 389 voges , w. , et al . 2000 , , 7432 , 1 zuckerman , b. , & song , i. 2004 , , 42 , 685 zuckerman , b. , song , i. , & bessell , m. s. 2004 , , 613 , l65

we present results of a high - resolution , near - infrared survey of 41 nearby , young ( ) m0m5.0 dwarfs using the altair natural guide star adaptive optics system at the gemini north telescope . statistical properties are studied and compared with earlier ( f to k ) and later ( m6 very low - mass , vlm ) populations . we exclude the existence of physical companions with masses greater than 10 jupiter masses ( ) at separations of and masses greater than for separations around 37 of the 41 observed objects .

we present results of a high - resolution , near - infrared survey of 41 nearby , young ( ) m0m5.0 dwarfs using the altair natural guide star adaptive optics system at the gemini north telescope . twelve of the objects appear to be binaries , 7 of which are reported here for the first time . one triple system was discovered . statistical properties are studied and compared with earlier ( f to k ) and later ( m6 very low - mass , vlm ) populations . we find that the separation distribution of the binaries in this sample peaks at , which is consistent with previous measurements of early - m binaries . hence , early - m binaries seem to occur in on average tighter systems than g binaries . at the same time they are significantly wider than field vlm binary stars . the distribution of mass ratios of primary and secondary stars was found to show an intermediate distribution between the strongly peaked distribution of field vlm systems and the almost flat distribution of earlier - type stars . consequently , we show evidence for relatively young , early - m binaries representing a transition between the well known earlier star distributions and the recently examined field vlm population characteristics . despite the fact that this survey was dedicated to the search for faint brown dwarf and planetary mass companions , all planetary mass candidates were background objects . we exclude the existence of physical companions with masses greater than 10 jupiter masses ( ) at separations of and masses greater than for separations around 37 of the 41 observed objects .

astro-ph0211189

i

the large absorption line red shift measurements settled the issue that most @xmath0-ray bursts are at cosmological distances . the physical mechanism of the origin of the @xmath0-ray bursts , questions of whether there are more than one mechanism , and the issue of whether @xmath0-ray bursts interact only with the interstellar medium or with a circumstellar environment are still very open . correlations with star formation and observations of putative iron lines with the chandra observatory @xcite have put new focus on the connection to a supernova - like core collapse event . currently , most observations of @xmath0-ray burst afterglows are photometric , with the effort being to find the power law behavior of the afterglow brightness as a function of wavelength and time . most of the 25 known red shifts have been measured by deep spectroscopy on the host galaxy long after the afterglow has faded . prior to grb 021004 , only eight @xmath0-ray burst afterglows have had early - time spectra that reveal absorption lines from the host galaxy ( e.g. , vreeswijk et al . 2001 ) . of these , virtually all have been low excitation lines in one velocity system that are likely to arise in gas far from the burster . two exceptions to this are grb 011211 which shows and in addition to lower excitation lines @xcite , and grb 010222 which displayed two low - ionization systems separated by @xmath6 km s@xmath1 that could arise from clouds at different positions within the host galaxy @xcite . grb 020813 has a spectrum which displays absorption lines in both a z=1.223 and z=1.255 systems @xcite . with so little known , and many afterglows revealing new properties , more prompt spectroscopy is clearly needed . afterglow spectra could show absorption lines arising from the host galaxy ( especially the fe and mg ism lines ) that will give the red shift . the red shift is the key parameter for determining the burst energetics and hence further testing the conclusions of @xcite and @xcite that @xmath0-ray bursts have a nearly constant total energy . one can also improve the calibration ( currently based on 9 events , see also schaefer , deng , & band 2000 ) that the spectral lags and light curve variability are cepheid - like luminosity indicators that could turn @xmath0-ray burstsinto a premier tool for cosmology out to z@xmath410 @xcite . intrinsic afterglow spectral features of any kind would be a boon to interpretation . if there are underlying supernova - like explosions , corresponding spectral features could be superposed on the continuum and revealed by careful subtraction of the well - defined power - law continuum . detection of , for instance , features of red shifted ca h & k , which tend to be among the strongest lines in all types of supernovae , would yield both a red shift and clues to the nature of the explosion itself . other possibilities would be to discover fe emission lines , which would yield temperatures , red shifts , and abundances . perhaps the most important possibility is that of serendipitous discovery of some unexpected feature . grb 021004 provided an unprecedented opportunity to obtain prompt spectroscopy of the early afterglow of a @xmath0-ray burst . grb 021004 was discovered by instruments on the hete ii satellite at 12:06 ut on 2002 october 4 @xcite . prompt discovery of the optical transient by @xcite allowed rapid spectroscopic observations . @xcite obtained the first spectra and identified two intervening systems at z = 1.38 and 1.60 from and absorption . @xcite confirmed those features , noted several absorptions at these redshifts , and pointed out four absorption lines at @xmath4 4633 , 4664 , 5109 , and 5152 ( see also sahu et al . 2002 ; castander et al . these were identified by @xcite as and features at red shift of @xmath7 . chornock & filippenko also identified ly@xmath8 emission at z = 2.323 and absorption components and perhaps ly@xmath9 at similar red shifts . @xcite identified four absorption components of at z = 2.295 , 2.298 , 2.230 and 2.237 , noting that the total spread is about 3000 km s@xmath1 . they remarked that this velocity dispersion would be difficult to interpret as due to a single cluster of galaxies and noted that if associated with a supernova shell the supernova must have substantially preceeded the @xmath0-ray burst to be optically thin . @xcite suggested the identification of one absorption feature as low excition at z = 2.328 and identified that , and the ly@xmath8 emission , as the red shift of the host galaxy . they raised the issue of the velocity dispersion being due to a wind in a wolf - rayet like progenitor . @xcite noted that the ly@xmath8 flux may imply a strong star formation rate in the host galaxy . @xcite reported a very high resolution spectrum ( r = 50,000 ) that revealed the complex fine structure of many of the high ionization lines . they determined that the individual features show complex flow spanning about 1000 km s@xmath1 and conclude that the @xmath10 system is probably close to the @xmath0-ray burst . they note that of the four high red shift systems , the low ionization lines , and possibly , only occur in the highest red shift , @xmath10 , component . @xcite and mller et al . ( 2002 ) have provided an excellent compendium of line identifications along with detailed line profiles . @xcite give a spectral index in the optical of @xmath11 , and report a reddening of the continuum in the blue region of the spectrum over the first three days . here we report spectra obtained within the first day after outburst and five days later . we concentrate on constraining the circumburst medium in the context of the high ionization lines and the afterglow light curve .

we delineate six components in the medium surrounding the-ray burst along the line of sight : ( 1 ) the absorption lines arise from the innermost region closest to the burst , where the ionization will be highest and the 3000 km s velocity comes from the intrinsic velocity of a massive star wind boosted by acceleration from the burst flux . for a mass loss rate of

we present spectra of the optical transient of grb 021004 obtained with the hobby - eberly telescope starting 15.48 , 20.31 hours , and 4.84 days after the-ray burst and a spectrum obtained with the h. j. smith 2.7 m telescope starting 14.31 hours after the-ray burst . grb 021004 is the first burst afterglow for which the spectrum is dominated by absorption lines from high ionization species with multiple velocity components separated by up to 3000 km s . we argue that these absorption lines are likely to come from shells around a massive progenitor star . the high velocities and high ionizations arise from a combination of acceleration and flash - ionization by the burst photons and the wind velocity and steady ionization by the progenitor . we also analyze the broad - band spectrum and the light curve so as to distinguish the structure of gas within 0.3 pc of the burster . we delineate six components in the medium surrounding the-ray burst along the line of sight : ( 1 ) the absorption lines arise from the innermost region closest to the burst , where the ionization will be highest and the 3000 km s velocity comes from the intrinsic velocity of a massive star wind boosted by acceleration from the burst flux . for a mass loss rate of , this component also provides the external medium with which the jet collides over radial distances 0.0040.3 pc to create the afterglow light . ( 2 ) a second cloud or shell produces absorption lines with a relative velocity of 560 km s . this component could be associated with the shell created by the fast massive star wind blowing a bubble in the preceding slow wind at a radial distance of order 10 pc or by a clump at 0.5 pc accelerated by the burst . ( 3 ) more distant clouds within the host galaxy that lie between 30 - 2500 pc and have been ionized by the burst will create the absorption lines . ( 4 - 6 ) if the three bumps in the afterglow light curve at 0.14 , 1.1 , and 4.0 days are caused by clumps or shells in the massive star wind along the line of sight , then the radii and over - densities of these are 0.022 , 0.063 , and 0.12 parsecs and 50% , 10% , and 10% respectively . the immediate progenitor of the-ray burstcould either be a wc - type wolf - rayet star with a high velocity wind or a highly evolved massive star the original mass of which was too small for it to become a wn - type wolf - rayet star . in summary , the highly ionized lines with high relative velocities most likely come from shells or clumps of material close to the progenitor and these shells were plausibly produced by a massive star soon before its collapse .

astro-ph0211189

c

the grb 021004 spectrum displays high - ionization and high - velocity absorption lines . we argue that these lines are likely to have arisen from shells of gas around the progenitor star , and further , that these shells plausibly come from a progenitor that was descended from a massive star . the gas in these shells was partially ionized and accelerated by the photons from the burst . we have used the optical spectrum , the broad - band spectrum , and the light curve to identify six components in the medium external to the @xmath0-ray burst . the @xmath2 absorption lines arise from a shell at a radial distance of less than a parsec that is moving at a velocity of 3000 km s@xmath1after being ionized and accelerated by the burst radiation . we identify this component as being the wind from the progenitor star , perhaps a wolf - rayet star with a mass loss rate of @xmath151 or a lower mass star wind accelerated by the bust . this same component provides the external medium with which the jet is colliding to produce the afterglow light . this inner component is probably significantly clumped in order to prevent complete ionization and to facilitate recombination , thus allowing a significant column depth of . the second component is associated with the absorption lines moving 560 km s@xmath1 with respect to the host galaxy velocity . we identify this component as arising from a shell of material plowed up by the wolf - rayet - like wind at a radius of order 10 parsecs . alternatively , this feature could be a shell or clump at @xmath4 0.5 pc accelerated by the burst . the third component gives rise to the low - velocity high - excitation absorption lines which must come from a distance between tens and hundreds of parsecs from the burster . this component might be from the shell created by the o main sequence star wind or it might be from chance ism clouds along the line of sight , perhaps part of the same star forming region that gave birth to the @xmath0-ray burstprogenitor . the fourth , fifth , and sixth components are three density enhancements that occur in the wolf - rayet - like wind at radial distances of 0.022 , 0.063 , and 0.12 pc so as to produce the three bumps in the light curve . these clumps could be related to the clumping we deduce for component 1 , that is , all could be associated with knots in the progenitor wind . the results summarized in the previous paragraph offer a plausible description of the density structure near this burst . what we see is a variety of density enhancements along the line of sight , with the evidence coming from bumps in the light curve decline and absorption lines in the spectrum . this picture is apparently not universal for @xmath0-ray bursts , since only two out of nine bursts with well - observed afterglow spectra show both high - excitation and high - velocity lines . the other bursts must have some mechanism for suppressing similar absorption lines . a full analysis is needed for the @xmath12 lines of grb 021004 , with the possibility of determining the abundance of the progenitor s shell and hence to obtain information about the progenitor itself . as a start to this program , we have shown that the nitrogen in the shell is under - abundant with respect to the carbon , and this demonstrates that the progenitor was not a wn - type wolf - rayet star and further that the progenitor was either one of the more massive wolf - rayet stars or a massive star that is below that required to make a wn - type star . a further program for our community is to obtain high dispersion spectroscopy so as to be able to measure fine velocity structures and faint lines in the afterglow spectra of many bursts . the most important result from our data and analysis is that a plausible way to create the high - excitation and high - velocity absorption lines is to have shells of gas surrounding the progenitor , and that a realistic way to achieve this is for the progenitor to be a star descended from a massive o - type main sequence star . this strongly suggested connection to a massive star is much more direct than the moderate statistical association of @xmath0-ray bursts with parts of galaxies undergoing star formation and is much more convincing than attributing poorly observed bumps in afterglow light curves to some associated supernova event . as such , we believe that the absorption lines in the grb 021004 spectra provide the first strong and direct argument for associating a normal @xmath0-ray burst with a massive progenitor star surrounded by shells . we thank bruce draine , bev wills , greg shields , and d. j. hillier for their discussion on a wide range of topics . this work was supported in part by nasa grant nag59302 and nsf grant ast-0098644 . the marcario low resolution spectrograph is a joint project of the hobby - eberly telescope partnership and the instituto de astronomia de la universidad nacional autonoma de mexico . the hobby - eberly telescope is operated by mcdonald observatory on behalf of the university of texas at austin , the pennsylvania state university , stanford university , ludwig - maximilians - universitt mnchen , and georg - august - universitt gttingen . ccccc @xmath152 & si iv & 1393.8 & @xmath153 & 2.291 + @xmath154 & si iv & 1393.8 & @xmath155 & 2.321 + @xmath154 & si iv & 1402.8 & @xmath155 & 2.299 + @xmath156 & si iv & 1402.8 & @xmath157 & 2.326 + @xmath158 & c iv & 1548.2 & 1550.8 & @xmath159 & 2.296 + @xmath160 & c iv & 1548.2 & 1550.8 & @xmath161 & 2.325 + @xmath162 & al ii & 1670.8 & @xmath163 & 2.328 + @xmath164 & n v & 1238.8 & 1242.8 & @xmath165 & @xmath166

we argue that these absorption lines are likely to come from shells around a massive progenitor star . we also analyze the broad - band spectrum and the light curve so as to distinguish the structure of gas within 0.3 pc of the burster . , this component also provides the external medium with which the jet collides over radial distances 0.0040.3 pc to create the afterglow light . the highly ionized lines with high relative velocities most likely come from shells or clumps of material close to the progenitor and these shells were plausibly produced by a massive star soon before its collapse .

we present spectra of the optical transient of grb 021004 obtained with the hobby - eberly telescope starting 15.48 , 20.31 hours , and 4.84 days after the-ray burst and a spectrum obtained with the h. j. smith 2.7 m telescope starting 14.31 hours after the-ray burst . grb 021004 is the first burst afterglow for which the spectrum is dominated by absorption lines from high ionization species with multiple velocity components separated by up to 3000 km s . we argue that these absorption lines are likely to come from shells around a massive progenitor star . the high velocities and high ionizations arise from a combination of acceleration and flash - ionization by the burst photons and the wind velocity and steady ionization by the progenitor . we also analyze the broad - band spectrum and the light curve so as to distinguish the structure of gas within 0.3 pc of the burster . we delineate six components in the medium surrounding the-ray burst along the line of sight : ( 1 ) the absorption lines arise from the innermost region closest to the burst , where the ionization will be highest and the 3000 km s velocity comes from the intrinsic velocity of a massive star wind boosted by acceleration from the burst flux . for a mass loss rate of , this component also provides the external medium with which the jet collides over radial distances 0.0040.3 pc to create the afterglow light . ( 2 ) a second cloud or shell produces absorption lines with a relative velocity of 560 km s . this component could be associated with the shell created by the fast massive star wind blowing a bubble in the preceding slow wind at a radial distance of order 10 pc or by a clump at 0.5 pc accelerated by the burst . ( 3 ) more distant clouds within the host galaxy that lie between 30 - 2500 pc and have been ionized by the burst will create the absorption lines . ( 4 - 6 ) if the three bumps in the afterglow light curve at 0.14 , 1.1 , and 4.0 days are caused by clumps or shells in the massive star wind along the line of sight , then the radii and over - densities of these are 0.022 , 0.063 , and 0.12 parsecs and 50% , 10% , and 10% respectively . the immediate progenitor of the-ray burstcould either be a wc - type wolf - rayet star with a high velocity wind or a highly evolved massive star the original mass of which was too small for it to become a wn - type wolf - rayet star . in summary , the highly ionized lines with high relative velocities most likely come from shells or clumps of material close to the progenitor and these shells were plausibly produced by a massive star soon before its collapse .

astro-ph0610135

r

in [ sys ] we discuss possible sources of systematic error both in the measurements from the x - ray data and the theoretical predictions . possible systematic errors affecting the x - ray mass measurements of our sample of relaxed galaxies and clusters are expected to be small and do not change the conclusions of the analysis presented here ( see beginning of [ sys ] and [ he ] ) . when fitting the power - law relation ( eqn . [ eqn.cm ] ) to the entire sample we obtain @xmath124 and @xmath125 ( quoted errors @xmath126 ) . the estimated intrinsic scatter in @xmath127 is @xmath128 ( eqn . [ eqn.scat ] ) , with a total scatter of 0.12 . in figure we plot the best - fitting model with intrinsic scatter . inspection of figure [ fig.cm ] reveals that the power - law with intrinsic scatter is a good approximate representation of the x - ray results , especially for @xmath129 . for lower masses the x - ray measurements tend to lie above the best - fitting model , though most are consistent with lying within the @xmath126 range covered by the intrinsic scatter . using equation [ 3 ] of @xcite we compute a reduced @xmath130 value of 1.07 ( 37 dof ) for the fit , confirming the visual impression that the power law is a good , but not perfect , representation of the x - ray data . the slope @xmath63 is constrained to be negative at the @xmath4 level , demonstrating at high significance that @xmath0 decreases with increasing @xmath1 , as expected in cdm models . in figure [ fig.cm ] we also plot the theoretical @xmath3 relation for the model for both @xmath107 and @xmath110 as discussed in [ models ] . for @xmath131 the @xmath110 model recommended by d04 for clusters lies very close to , but just below , the empirical power - law fit . allowing for a systematic @xmath15 increase in concentration for relaxed , early forming halos @xcite lifts the @xmath110 model slightly over the power - law , with a marginal improvement in the agreement between the models . a recent theoretical study @xcite finds that the higher mass halos experience less of bias associated with relaxation and formation time . in fact , systematically increasing the concentrations of the @xmath110 model by @xmath132 would provide a closer match to the empirical power - law fit to the x - ray data . for @xmath133 the @xmath110 model must quickly transform into the @xmath107 model as @xmath1 decreases from the cluster to the galaxy / group regime as discussed in [ models ] . but in this mass range the @xmath107 model lies consistently below the power - law model and is similar to the @xmath126 lower limit on the power - law given by the intrinsic scatter . increasing the concentrations of the @xmath107 model by @xmath15 for relaxed halos improves the agreement with the power - law , and has the effect of essentially pushing the @xmath107 model into the @xmath110 model . with this accounting for the systematic bias arising from relaxed , early forming halos the model is an equally good representation of the x - ray data for masses @xmath134 . for the lowest masses , the model still lies below the power - law ( within the @xmath126 intrinsic scatter ) and may represent a real discrepancy . we summarize this qualitative discussion with a quantitative comparison of the model with the data as represented by the results of the empirical power - law fit . ( we do not fit the b01 model to the data for the following reasons . first , it is non - trivial to account for the error bars in both coordinates when fitting a general model ; the akritas & bershady method only applies to linear regression . second , the prediction of the b01 model possesses significant systematic uncertainty in the parameter @xmath94 ( at least for masses @xmath135 ) as discussed above . by showing the b01 model predictions separately for the range of interesting k values , without fitting , we provide a clear demonstration of the importance of reducing this systematic uncertainty with future theoretical studies . when that happens , formal fitting of the b01 model will be investigated . ) in figure [ fig.errors ] we show the error contours estimated for @xmath63 and @xmath62 from the bootstrap simulations ( [ method ] ) . we calculated the slope and concentration of the @xmath3 relation of the model at @xmath136 for both the @xmath107 and @xmath110 cases . ( the values for @xmath110 are listed in table [ tab.models.cm ] . ) these results are plotted in figure [ fig.errors ] as `` 1 '' for @xmath107 and @xmath137 for @xmath110 , the latter representing the `` cluster '' regime . the right panel of figure [ fig.errors ] increases the concentrations by 10% to represent relaxed , early forming systems , and shows the model lies near the @xmath138 confidence contour . this level of agreement applies for masses @xmath129 . as discussed above , the agreement is worse at the lowest masses . however , performing a similar comparison at @xmath139 we find the local slope and normalization lie just within the 95% confidence contour of the power - law model ( both with and without the 10% correction for relaxed systems ) ; i.e. , the disagreement is not very significant even at the low - mass end . if real , the discrepancy may signify very early forming fossil groups in the sample @xcite . the intrinsic scatter of 0.10 in @xmath127 obtained for the power - law fit is smaller than the value of 0.14 for all dark matter halos in cdm simulations but agrees extremely well with the value expected for the most relaxed , early forming systems @xcite . consideration of this result for the scatter and the average @xmath3 relation above , we conclude that the model is consistent with the x - ray data , provided the x - ray sample reflects the most relaxed , early forming systems in the population . ( this corroborates our selection criteria discussed in [ obs ] . ) now we perform the analogous comparison of the model with the x - ray data and associated power - law fit . the @xmath3 relation is displayed in the right panel of figure [ fig.cm ] . the model lies well - below the power - law at all masses , even when allowing for the expected 10% increase in concentration for relaxed halos . in figure [ fig.errors ] we compare the model at @xmath136 with the empirical power - law . even when considering the 10% increase in concentrations for relaxed halos , the model lies on the 99.99% contour . systematic errors associated with the x - ray measurements can not explain this level of disagreement ( see [ sys ] ) . the key parameter responsible for the poor performance of the model with respect to is the low value of ( 0.76 ) . in order to bring the model within the 99% contour in the right panel of figure [ fig.errors ] requires @xmath140 where we have kept the other cosmological parameters fixed to their values in table [ tab.models ] . this limit is conservative since ( 1 ) we use @xmath110 , ( 2 ) we assume a full 10% upward shift for the bias from relaxed , early forming systems , which may be less for massive clusters , and ( 3 ) we have approximated the b01 models as power - laws using their predictions only near @xmath136 . the sensitivity of the concentrations to results from the impact that has on the average halo formation times ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? other cosmological parameters , however , contribute to the large discrepancy of the model . if we remove the tilt of the power spectrum ( i.e. , set @xmath141 ) then we obtain @xmath142 at the 99% confidence level . finally , if we further set @xmath5 and @xmath143 ( so the model is the same as except with variable ) , then the 99% constraint falls to @xmath144 , the value associated with the model . ( we reiterate this limit is conservative as noted above . similarly , we obtain @xmath145 at 99% confidence , where the @xmath107 model is used here to be conservative . ) hence , although the lower value of is the primary cause of the poor performance of the model , the combined action of the power - spectrum tilt with the lower value of exacerbate the discrepancy with the x - ray @xmath3 relation . if the parameters are correct , particularly the low value of , then a fundamental modification of the model is required to increase the concentration values to match the x - ray results . both d04 and @xcite have shown that changing the dark energy equation of state parameter ( @xmath26 ) has the effect of systematically raising ( larger @xmath26 ) or lowering ( smaller @xmath26 ) halo concentrations . as we show below , a model with @xmath10 and @xmath146 can describe the x - ray data in the cluster regime . results of fitting eqn . [ eqn.cm ] in log space only for halos with @xmath29 . displayed are the best - fitting model ( solid blue line ) and the @xmath126 intrinsic scatter ( dotted blue lines ) . also shown is the predicted relation for the model from cosmological simulations . the ( solid red ) line is the power - law fit obtained by d04 while the ( dashed red ) line is the b01 model with @xmath105 and @xmath110 found by d04 to best match the simulated clusters . note the d04 model is converted to our definition of the virial radius ( [ models ] ) . ] as discussed in [ models ] , d04 provide results of fitting eqn.to a suite of cdm models for massive clusters , including an open model and multiple dark energy models . we may compare these theoretical predictions directly to the power - law fit to the x - ray data with the following considerations . firstly , we convert d04 s results to our definition of the virial radius ( see [ models ] ) . secondly , since d04 analyze only massive clusters ( @xmath147 , @xmath35 and converted to @xmath114 ) , we restrict our analysis to high - mass systems as well . in order to allow more precise constraints on the power - law fit we consider clusters down to a somewhat smaller mass limit , @xmath148 . ( as shown below , this choice is justified since there is no obvious trend in the @xmath3 relation over this mass range . ) finally , we need to consider the biases ( @xmath15 higher @xmath0 , smaller scatter in @xmath30 ) for relaxed , early forming systems as done for the whole sample in the previous section . however , the systematic increase in @xmath0 may be less since we are considering the most massive systems @xcite . in figure [ fig.cm.clusters ] we show the result of fitting eqn.to the high - mass sample , for which we obtain the following parameter constraints , @xmath149 and @xmath150 . these parameters are consistent with a constant @xmath3 relation , as well as profiles that both decrease and increase with increasing @xmath1 , and agree well with similar fits obtained in this mass range from previous x - ray studies with either _ xmm _ @xcite or _ chandra _ @xcite . since the power - law fit is quite consistent with @xmath151 , it follows that it is the lower mass systems ( @xmath135 ) which require @xmath152 found when fitting the whole sample in the previous section ( see * ? ? ? ( note that the power - law parameters inferred in the previous section for the full sample lies on the 99% confidence contour obtained for the fit to the high - mass subsample see figure [ fig.errors.clusters ] . ) we measure an intrinsic scatter in @xmath127 of @xmath153 which is somewhat less than the value of 0.10 obtained for the entire sample . d04 also obtain 0.10 for the intrinsic scatter ( after accounting for a factor of 2.3 converting @xmath122 to ) for all of their cdm clusters . the smaller scatter we measure presumably can be explained because the x - ray sample preferentially contains relaxed , early forming systems . for comparison we plot two versions of the model in figure [ fig.cm.clusters ] . the first version we show is the power - law fit obtained by d04 converted to our definition of the virial radius ( see [ models ] ) . the second version arises from using the b01 model with @xmath110 , which d04 found to best represent their high - mass cluster simulations . both models are very similar and provide a reasonable description of the x - ray data , though the b01 representation is slightly steeper . in the left panel of figure [ fig.errors.clusters ] we plot the power - laws obtained by d04 for the cdm models as well as the b01 representation of the model with @xmath110 . the values of @xmath63 and @xmath62 for all of these models ( table [ tab.models.cm ] ) are plotted in the right panel of figure [ fig.errors.clusters ] along with the error contours derived from the power - law fit to the x - ray data . as done in the previous section , the @xmath63 and @xmath62 values for the b01 model were obtained using the @xmath3 slope near @xmath154 . we emphasize that the d04 parameters may be compared directly to the results of our power - law fit to the x - ray data , since the same model is fitted over nearly the same mass range . since the b01 representation of the model is very nearly a power - law over the range being investigated , a similarly direct comparison is appropriate . the results for the and models obtained using only the high - mass subsample corroborate those obtained from the full sample . as noted above , the model is an acceptable match to the x - ray data ; the parameters lie near the 68% confidence contour in figure [ fig.errors.clusters ] , even if @xmath0 is increased to correct for early forming halos . in contrast , the model is very inconsistent with the high mass data , with parameters lying outside the 99.99% contour . even if we apply the full 10% correction to @xmath62 appropriate for the most relaxed , early forming systems , then the model merely moves on top of the 99.99% contour . however , as noted above , it is expected that this correction is less for the highest mass systems . hence , the model is also rejected using only the most massive clusters . the @xmath3 data for high - mass clusters clearly exclude the ocdm model . the concentrations lie systematically above the data and the model . the latter is expected because structures form earlier in the ocdm model . in principle , the ocdm model may be brought into acceptable agreement with the x - ray data by lowering . we estimate the effect of lowering using the b01 model . for example , lowering @xmath8 from 0.90 to 0.70 lowers @xmath62 by 25% . this would move the ocdm model to the right in figure [ fig.errors.clusters ] on to the 99% confidence contour . considering any of the 10% systematic bias expected for early forming systems would increase the discrepancy . ( note that for @xmath155 , appropriate for the model , the ocdm model would be rejected at the @xmath156 confidence level without additional consideration of early formation bias . ) studies of the abundances of galaxy clusters using weak gravitational lensing typically find consistent with 0.9 ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? the optical study of @xcite uses the caustic technique to measure cluster abundances and also finds @xmath157 with a lower limit of 0.72 ( 95% conf . ) . however , x - ray studies of cluster abundances show a large variation in , with values ranging from 0.7 - 0.9 ( see * ? ? ? * and references therein ) . the x - ray studies use a simple conversion between mass and global temperature or mass and global x - ray luminosity ( @xmath158 ) . a recent study by @xcite argues that considering reasonable errors in the @xmath159 conversion allows agreement of cluster abundances with the recent wmap parameters with @xmath160 and @xmath161 though see @xcite . we take @xmath162 to be a conservative lower limit established by the abundances of galaxy clusters . therefore , an open cdm model with @xmath163 is ruled out ( @xmath11 confidence ) from joint consideration of only the x - ray @xmath3 relation and cluster abundances . since @xmath8 and @xmath13 are tightly coupled from cluster abundance studies , and all the studies cited above give @xmath164 for @xmath12 , using the x - ray @xmath3 data we find that we can also exclude cdm models with @xmath12 at high significance ( @xmath165 confidence ) . for this comparison we have employed the entire sample of 39 systems and have set @xmath166 for the @xmath12 models to better satisfy cosmic age constraints from stellar populations in globular clusters @xcite . consequently , the combination of the x - ray @xmath3 relation and cluster abundances , assisted by constraints on the cosmic age , provides novel evidence for a flat , low-@xmath13 universe with dark energy using observations only in the local ( @xmath14 ) universe . finally , we consider the alternative dark energy models , decdm and qcdm . the decdm model lies systematically above the model and deviates from the power - law fit to the x - ray data at the 99.9% confidence level . this behavior is expected since @xmath90 implies halos form earlier compared to the @xmath167 model ( see also * ? ? ? * ) . by lowering it should be possible to bring the decdm model into good agreement with the data . to illustrate this trade - off between @xmath26 and , we consider the qcdm model which has @xmath10 and @xmath168 . as shown in figure [ fig.errors.clusters ] the qcdm model matches the x - ray results nearly as well as the model . in fact , a mild increase in @xmath62 owing to effect from selecting relaxed , early forming halos would produce even better agreement . our analysis indicates that a model similar to qcdm is able to satisfy the most recent constraints from other cosmological observations since @xmath10 is marginally consistent with the constraints imposed by supernovas ( @xmath169 , * ? ? ? * ) , and @xmath168 is also marginally consistent with the 3-yr wmap results . put another way , if the low value of is correct , then the x - ray @xmath3 data imply @xmath170 .

a power - law model fitted to the x - ray relation requires at high significance ( ) that decreases with increasing , which is a general feature of cdm models . the median and scatter of the relation produced by the flat , concordance model ( , ) agrees with the x - ray data provided the sample is comprised of the most relaxed , early forming systems , which is consistent with our selection criteria . this result provides novel evidence for a flat , low- universe with dark energy using observations only in the local ( ) universe . possible systematic errors in the x - ray mass measurements of a magnitude suggested by cdm simulations do not change our conclusions .

we present the concentration ()-virial mass ( ) relation of 39 galaxy systems ranging in mass from individual early - type galaxies up to the most massive galaxy clusters , . we selected for analysis the most relaxed systems possessing the highest quality data currently available in the _ chandra _ and _ xmm _ public data archives . a power - law model fitted to the x - ray relation requires at high significance ( ) that decreases with increasing , which is a general feature of cdm models . the median and scatter of the relation produced by the flat , concordance model ( , ) agrees with the x - ray data provided the sample is comprised of the most relaxed , early forming systems , which is consistent with our selection criteria . holding the rest of the cosmological parameters fixed to those in the concordance model the relation requires ( 99% conf . ) , assuming a 10% upward bias in the concentrations for early forming systems . the tilted , low- model suggested by a new wmap analysis is rejected at confidence , but a model with the same tilt and normalization can be reconciled with the x - ray data by increasing the dark energy equation of state parameter to . when imposing the additional constraint of the tight relation between and from studies of cluster abundances , the x - ray relation excludes ( conf . ) both open cdm models and flat cdm models with . this result provides novel evidence for a flat , low- universe with dark energy using observations only in the local ( ) universe . possible systematic errors in the x - ray mass measurements of a magnitude suggested by cdm simulations do not change our conclusions . we discuss other sources of systematic error in the measurements and theoretical predictions that need to be addressed for future precision cosmological studies using the relation .

astro-ph0610135

c

we present the concentration ( @xmath0)-virial mass ( @xmath1 ) relation of 39 galaxy systems ranging in mass from individual early - type galaxies up to the most massive galaxy clusters , @xmath2 . we selected for analysis the most relaxed systems possessing the highest quality data currently available in the _ chandra _ and _ xmm _ public data archives . measurements for 24 systems were taken from our recent work @xcite which populate the lower mass portion of the sample ( @xmath197 ) . we obtained results for 15 massive galaxy clusters in our sample from the studies by @xcite and @xcite . our principal objective is to measure the @xmath3 relation accurately from galaxy to cluster scales and determine whether @xmath0 decreases with increasing @xmath1 as generally predicted by cdm models . however , we also use the @xmath3 relation to provide an initial demonstration of the ability of the @xmath3 relation to constrain cosmological parameters , which also serves to highlight key sources of systematic error both in the theoretical models and the observations . we parameterize the x - ray @xmath3 relation using a simple power - law model . the best estimates of the parameters the slope ( @xmath63 ) and normalization ( @xmath62 ) evaluated at @xmath198 were obtained via linear regression in log space taking into account the uncertainties on both @xmath0 and @xmath1 . we employed the bces method of @xcite for this analysis . fitting the power - law model to the entire sample yields @xmath124 and @xmath125 ( quoted errors @xmath126 ) . the slope @xmath63 is negative and inconsistent with 0 at @xmath4 . the previous studies of galaxy clusters ( @xmath193 ) with _ chandra _ and _ xmm _ by @xcite and @xcite did not place strong constraints on @xmath63 , and were quite consistent with @xmath151 ; i.e. , it is the lower mass galaxy groups that require @xmath152 ( see * ? ? ? recent optical studies of the @xmath3 relation in the group - cluster regime ( see [ intro ] ) also do not place strong constraints on the slope and are very consistent with @xmath199 . our analysis , therefore , provides crucial evidence that @xmath0 decreases with increasing @xmath1 , as expected in cdm models ( @xcite ; b01 ; d04 ; @xcite ) . we compare the x - ray data to the model ( with @xmath5 , @xmath6 , @xmath141 ) , the `` concordance model '' effectively representing the combined constraints from the first year of wmap cmb data , supernovae , and galaxy surveys ( e.g. , * ? ? ? we judge the median @xmath3 relation of the model to be consistent with the empirical power - law fit provided the x - ray sample consists of the most relaxed , early forming systems , for which a systematic increase in the concentrations of @xmath15 is expected @xcite . we measure an intrinsic scatter in @xmath127 of @xmath128 in excellent agreement with the prediction of cdm simulations for the most relaxed , early forming systems . the amount of scatter is a robust prediction of cdm variants and provides additional evidence that our sample comprises the most relaxed systems that are best suited for x - ray mass measurements requiring approximate hydrostatic equilibrium . the x - ray @xmath3 relation places interesting constraints on . within the context of the concordance model noted above , the @xmath3 relation requires @xmath7 ( 99% conf . ) , assuming a 10% upward bias in the concentrations for early forming systems . this confidence range is conservative as explained in [ all ] . next we compare the x - ray data to the model ( with @xmath161 , @xmath143 , @xmath155 , @xmath200 ) which effectively updates the model using the analysis of the third year of wmap data @xcite . the x - ray @xmath3 relation rejects the model at the 99.99% confidence level . the primary reason for the poor performance of the model is the low value of , but the lower value of and the tilt of the power spectrum also contribute to the poor fit . for this comparison we have assumed a uniform bias for relaxed , early forming halos of @xmath201 , as suggested by numerical simulations . this bias would have to be @xmath202 to bring the model into agreement with the x - ray data . while the early - type galaxy and group - cluster mass halos @xmath203 studied here apparently prefer slightly higher concentrations than predicted for typical halos in the concordance @xmath204cdm model , the opposite is true for late - type galaxies ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? this may indicate that a selection / formation - time bias operates across the galaxy type spectrum , with late - type galaxies inhabiting the low - concentration tail of the distribution ( though see * ? ? ? * ; * ? ? ? since d04 provide results of power - law fits to the @xmath3 relations of massive clusters formed in a variety of cdm models , including an open model and several dark energy models , we analyze separately the x - ray @xmath3 relation for the 22 systems in our sample with @xmath29 . in this mass range we obtain @xmath62 and @xmath205 values consistent with those inferred from previous _ chandra _ and _ xmm _ studies in the cluster mass regime noted above @xcite . as also found for the entire sample , the @xmath3 relation of the high - mass subsample is consistent with the model and very inconsistent with the model . however , an open model with @xmath163 is ruled out ( @xmath11 confidence ) from joint consideration of only the x - ray @xmath3 relation and published constraints on from the analysis of the abundances of galaxy clusters ( @xmath206 , see [ clusters ] ) . since cluster abundance studies also find @xmath164 if @xmath12 , using the x - ray @xmath3 data we find that we can also reject cdm models with @xmath12 at a high significance level ( @xmath165 confidence ) . consequently , the combination of the x - ray @xmath3 relation and cluster abundances ( and local constraints on the age of the universe ) provides novel evidence for a flat , low-@xmath13 universe with dark energy using observations only in the local ( @xmath14 ) universe . if the values of , , and @xmath86 of the model are correct , agreement with the x - ray @xmath3 relation may be achieved by increasing the dark energy equation of state parameter @xmath26 . we find that a quintessence model with @xmath10 and @xmath168 performs nearly as well as the model , and the larger value of @xmath26 remains marginally consistent with supernova constraints @xcite . finally , we discuss key sources of systematic error associated with both the x - ray measurements and theoretical models that need to be addressed before the x - ray @xmath3 relation is suitable for precision cosmology . in particular , if the virial masses are systematically underestimated by @xmath117 , as suggested by cdm simulations , then we estimate that @xmath62 is increased by @xmath207 , less than the @xmath15 increase expected for selecting relaxed , early forming systems . this level of systematic error does not change the conclusions of our present study ( see [ he ] ) , but it will be important for future studies of precision cosmology . we thank a. cooray for discussions and comments on the manuscript . , p.j.h . , and . gratefully acknowledge partial support from nasa grants nng04ge76 g , issued through the office of space sciences long - term space astrophysics program , and nag5 - 13059 , issued through the office of space science astrophysics data program . partial support for this work was also provided by nasa through chandra award numbers go4 - 5139x and go6 - 7118x issued by the chandra x - ray observatory center , which is operated by the smithsonian astrophysical observatory for and on behalf of nasa under contract nas8 - 03060 . we also are grateful for partial support from nasa - xmm grants , nag5 - 13643 , nag5 - 13693 , nng04gl06 g , and nng05gl02 g .

we present the concentration ()-virial mass ( ) relation of 39 galaxy systems ranging in mass from individual early - type galaxies up to the most massive galaxy clusters , . we selected for analysis the most relaxed systems possessing the highest quality data currently available in the _ chandra _ and _ xmm _ public data archives . holding the rest of the cosmological parameters fixed to those in the concordance model the relation requires ( 99% conf . ) , assuming a 10% upward bias in the concentrations for early forming systems . the tilted , low- model suggested by a new wmap analysis is rejected at confidence , but a model with the same tilt and normalization can be reconciled with the x - ray data by increasing the dark energy equation of state parameter to . when imposing the additional constraint of the tight relation between and from studies of cluster abundances , the x - ray relation excludes ( conf . ) both open cdm models and flat cdm models with . we discuss other sources of systematic error in the measurements and theoretical predictions that need to be addressed for future precision cosmological studies using the relation .

we present the concentration ()-virial mass ( ) relation of 39 galaxy systems ranging in mass from individual early - type galaxies up to the most massive galaxy clusters , . we selected for analysis the most relaxed systems possessing the highest quality data currently available in the _ chandra _ and _ xmm _ public data archives . a power - law model fitted to the x - ray relation requires at high significance ( ) that decreases with increasing , which is a general feature of cdm models . the median and scatter of the relation produced by the flat , concordance model ( , ) agrees with the x - ray data provided the sample is comprised of the most relaxed , early forming systems , which is consistent with our selection criteria . holding the rest of the cosmological parameters fixed to those in the concordance model the relation requires ( 99% conf . ) , assuming a 10% upward bias in the concentrations for early forming systems . the tilted , low- model suggested by a new wmap analysis is rejected at confidence , but a model with the same tilt and normalization can be reconciled with the x - ray data by increasing the dark energy equation of state parameter to . when imposing the additional constraint of the tight relation between and from studies of cluster abundances , the x - ray relation excludes ( conf . ) both open cdm models and flat cdm models with . this result provides novel evidence for a flat , low- universe with dark energy using observations only in the local ( ) universe . possible systematic errors in the x - ray mass measurements of a magnitude suggested by cdm simulations do not change our conclusions . we discuss other sources of systematic error in the measurements and theoretical predictions that need to be addressed for future precision cosmological studies using the relation .

1308.4323

c

images of the densest 11 square degrees of the sgr dsph at @xmath18 , @xmath16 and @xmath37 were compiled into a catalogue of 2921920 sources , and cross - matched to other major optical and infrared catalogues in the literature . this catalogue was used to confirm the properties of the sgr dsph and the foreground galactic bulge population . comparison to stellar isochrones confirms that the spheroidal sgr dsph core is dominated by a population with [ fe / h ] @xmath71 1 dex , with a significant anti - correlation of [ @xmath2/fe ] and [ fe / h ] . from the distribution of the galaxy s stars , we find it well represented by an oval shape measuring approximately 4@xmath87 in galactic latitude and 2@xmath87 in galactic longitude . we find some evidence for a metallicity gradient in the galaxy , and place it at 24.3 @xmath4 2.3 kpc using isochrone fitting . although we can not accurately constrain the metallicity distribution of the sgr dsph galaxy s stars , the metal - poor populations make up @xmath529 per cent of the observed bright giants in the galaxy . the rgb bump and helium - burning giant branch clump of the southern edge of the galactic bulge are matched with isochrones . a match is found only for isochrones representing a younger population , or one of particularly high metallicity , high [ @xmath2/fe ] and/or high he / h . we consider a younger population of near - solar composition most likely , possibly with some @xmath2-element enhancement . we do not see evidence for a split rgb bump in the bulge population , though this may be attributable to our line of sight . the ongoing vvv survey ( @xcite ) is mapping the bulge regions with vista in the nir , and will provide complementary information on the sgr populations in the innermost regions .

these are consistent with the previously - reported properties of the sgr dsph core : namely that it is dominated by a population between [ fe / h ] 1 dex and solar , with a significant [/fe ] versus [ fe / h ] gradient . we find slight evidence to confirm a metallicity gradient in the sgr dsph and use isochrones to fit a distance of 24.3 2.3 kpc . we find no evidence for a split , peanut- or x - shaped bulge population in this line of sight ( , ) .

we present the deepest near - infrared ( ) photometry yet obtained of the sagittarius dwarf spheroidal ( sgr dsph ) , using vista to survey 11 square degrees centred on its core . we list locations and-band magnitudes for over 2.9 million sources in the field . we discuss the isolation of the sgr dsph from the foreground and galactic bulge populations , identify the sgr dsph s horizontal branch in the near - infrared for the first time , and map the density of the galaxy s stars . we present isochrones for the sgr dsph and bulge populations . these are consistent with the previously - reported properties of the sgr dsph core : namely that it is dominated by a population between [ fe / h ] 1 dex and solar , with a significant [/fe ] versus [ fe / h ] gradient . while strong contamination from the galactic bulge prevents accurate measurement of the ( galactic ) north side of the sgr dsph , the dwarf galaxy can be well - approximated by a roughly ovaloid projection of characteristic size , beyond which the projected stellar density is less than half that of the region surrounding the core . the galaxy s major axis is perpendicular to the galactic plane , as in previous studies . we find slight evidence to confirm a metallicity gradient in the sgr dsph and use isochrones to fit a distance of 24.3 2.3 kpc . we were unable to fully constrain the metallicity distribution of the sgr dsph due to the bulge contamination and strong correlation of [/fe ] with metallicity , however we find that metal - poor stars ( [ fe / h ] 1 ) make up per cent of the sgr dsph s upper - rgb population . the bulge population is best fit by a younger population with [ fe / h ] 0 and [/fe ] 0 or slightly higher . we find no evidence for a split , peanut- or x - shaped bulge population in this line of sight ( , ) . [ firstpage ] stars : late type stars : agb and post - agb stars : evolution stars : fundamental parameters galaxies : individual : sgr dsph galaxy : bulge

astro-ph0210645

i

one of the major thrusts in modern cosmology is an accurate census of star formation and star - forming galaxies in the universe . this endeavor forms the backbone for a slew of methods ( observational , analytical , and numerical ) to study the process of galaxy formation and evolution over cosmic time . to date , star - forming galaxies have been selected and studied mainly in two observational windows : the rest - frame ultraviolet ( uv ) , and rest - frame radio and far - infrared ( fir ) . for galaxies at high redshift these bands are shifted into the optical and radio / sub - mm , allowing observations from the ground . still , the problem of translating the observed emission to star formation rate ( sfr ) involves large uncertainty . this is partly because each band traces only a minor portion of the total energy output of stars . moreover , the optical / uv band is significantly affected by dust obscuration , thus requiring order of magnitude corrections , while the sub - mm and radio bands lack sensitivity , and therefore uncover only the most prodigiously star - forming galaxies . the main result that has emerged from star formation surveys over the past few years is exemplified in the so - called madau diagram . namely , the sfr volume density , @xmath10 , rises steeply to @xmath11 , and seemingly peaks at @xmath12 . there is still some debate about the how steep the rise is , with values ranging from @xmath13 @xcite to @xmath14 ( e.g. @xcite ) . the evolution beyond @xmath15 is even less clear since optical / uv observations indicate a decline @xcite , while recent sub - mm observations argue for a flat @xmath10 to higher redshift , @xmath16 @xcite . consistency with this trend can be obtained by invoking large dust corrections in the optical / uv @xcite . for general reviews of star formation surveys we refer the reader to @xcite , @xcite , and @xcite . despite the significant progress in this field , our current understanding of star formation and its redshift evolution is still limited by the biases and shortcomings of current optical / uv , sub - mm , and radio selection techniques . in particular , despite the fact that the optical / uv band is sensitive to galaxies with modest star formation rates ( down to a fraction of a m@xmath3 yr@xmath5 ) at high redshift , these surveys may miss the most dusty , and vigorously star - forming galaxies . moreover , it is not clear if the simple , locally - calibrated prescriptions for correcting the observed _ un - obscured _ sfr for dust extinction ( e.g. @xcite ) , hold at high redshift ; even if they do , these prescriptions involve an order of magnitude correction . finally , the optical / uv surveys are magnitude limited , and therefore miss the faintest sources . sub - mm surveys have uncovered a population of highly dust - extincted galaxies , which are usually optically faint , and have star formation rates of several hundred m@xmath3 yr@xmath5 ( e.g. @xcite ) . however , unlike optical / uv surveys , sub - mm surveys are severely sensitivity limited , and only detect galaxies with @xmath17 l@xmath3 . more importantly , current sub - mm bolometer arrays ( such as scuba ) have large beams on the sky ( @xmath18 arcsec ) making it difficult to unambiguously identify optical counterparts ( which are usually faint to begin with ) , and hence measure the redshifts @xcite ; in fact , of the @xmath19 sub - mm galaxies identified to date , only a handful have a measured redshift . finally , translating the observed sub - mm emission to a sfr requires significant assumptions about the temperature of the dust , and the dust emission spectrum ( e.g. @xcite ) . surveys at decimeter radio wavelengths also suffer from low sensitivity , but the high astrometric accuracy afforded by synthesis arrays such as the vla allows a sub - arcsec localization of the radio - selected galaxies . as a result , it is easier to identify the optical counterparts of these sources . recently , this approach has been used to pre - select sources for targeted sub - mm observations resulting in an increase in the sub - mm detection rate @xcite and redshift determination @xcite . however , this method is biased toward finding luminous ( high sfr ) sources since it requires an initial radio detection . an additional problem with radio , even more than with sub - mm , selection is contamination by active galactic nuclei ( agn ) . an examination of the x - ray properties of radio and sub - mm selected galaxies reveals that of the order of @xmath1 can have a significant agn component @xcite . the most significant problem with current star formation studies , however , is that the link between the optical and sub - mm / radio samples is still not well understood . the hubble deep field provides a clear illustration : the brightest sub - mm source does not appear to have an optical counterpart @xcite , and only recently a detection has been claimed in the near - ir ( @xmath20 mag ; @xcite ) . along the same line , sub - mm observations of the optically - selected lyman break galaxies have resulted in very few detections @xcite , and even the brightest lyman break galaxies appear to be faint in the sub - mm band @xcite . in addition , there is considerable diversity in the properties of optical counterparts to sub - mm sources , ranging from galaxies which are faint in both the optical and near - ir ( nir ) to those which are bright in both bands @xcite . as a result of the unclear overlap , and the sensitivity and dust problems in the sub - mm and optical surveys , the fractions of global star formation in the optical and sub - mm / radio selected galaxies is not well constrained . it is therefore not clear if the majority of star formation takes place in ultra - luminous galaxies with very high star formation rates , or in the more abundant lower luminosity galaxies with star formation rates of a few m@xmath3 yr@xmath5 . given the difficulty with redshift identification of sub - mm galaxies , the redshift distribution of dusty star forming galaxies remains highly uncertain . one way to alleviate some of these problems is to study a sample of galaxies that is immune to the selection biases of current optical / uv and sub - mm / radio surveys , and which may draw a more representative sample of the underlying distribution of star - forming galaxies . the host galaxies of @xmath0-ray bursts ( grbs ) may provide one such sample . the main advantages of the sample of grb host galaxies are : ( i ) the galaxies are selected with no regard to their emission properties in any wavelength regime , ( ii ) the dust - penetrating power of the @xmath0-ray emission results in a sample that is completely unbiased with respect to the global dust properties of the hosts , ( iii ) grbs can be observed to very high redshifts with existing missions ( @xmath21 ; @xcite ) , and as a result volume corrections for the star formation rates inferred from their hosts are trivial , ( iv ) the redshift of the galaxy can be determined via absorption spectroscopy of the optical afterglow , or x - ray spectroscopy allowing a redshift measurement of arbitrarily faint galaxies ( the current record - holder is the host of grb990510 with @xmath22 mag and @xmath23 ; @xcite ) , and ( v ) since there is excellent circumstantial evidence linking grbs to massive stars ( e.g. @xcite , the sample of grb hosts is expected to trace global star formation @xcite . of course , the sample of grb hosts is not immune from its own problems and potential biases . the main problem is the relatively small size of the sample in comparison to both the optical and sub - mm samples ( although the number of grb hosts with a known redshift exceeds the number of sub - mm galaxies with a measured redshift ) . as a result , at the present it is not possible to assess the sfr density that is implied by grb hosts , or its redshift evolution . a bias towards sub - solar metallicity for grb progenitors ( and hence their environments ) has been discussed @xcite , but it appears that very massive stars ( e.g. @xmath24 m@xmath3 ) should produce black holes even at solar metallicity . the impact of metallicity on additional aspects of grb formation ( e.g. angular momentum , loss of hydrogen envelope ) is not clear at present . finally , given the observed dispersion in metallicity within galaxies ( e.g. @xcite ) , it is likely that even if grbs require low metallicity progenitors , this does not imply that the galaxy as a whole has a lower than average metallicity . to date , grb host galaxies have mainly been studied in the optical and nir bands . with the exception of one source ( grb020124 ; @xcite ) , every grb localized to a sub - arcsecond position has been associated with a star - forming galaxy @xcite . these galaxies range from @xmath25 mag , have a median redshift , @xmath26 , and are generally typical of star - forming galaxies at similar redshifts in terms of morphology and luminosity @xcite , with star formation rates from optical spectroscopy of @xmath27 m@xmath3 yr@xmath5 . at the same time , there are hints for higher than average ratios of [ neiii]3869 to [ oii]3727 , possibly indicating the presence of massive stars @xcite . only two host galaxies have been detected so far in the radio ( grb980703 ; @xcite ) and sub - mm ( grb010222 ; @xcite ) . here we present sub - mm and radio observations of a sample of @xmath28 grb host galaxies , ranging in redshift from about @xmath29 to @xmath30 ( [ sec : obs ] ) ; one of the 20 sources is detected with high significance in both the sub - mm and radio bands , and an additional source is detected in the sub - mm ( [ sec : res ] ) . we compare the detected sub - mm and radio host galaxies to local and high-@xmath31 ultra - luminous galaxies in [ sec : sed ] , and derive the sfrs in [ sec : sfr ] . we then compare the inferred sfrs of the detected host galaxies , and the ensemble of undetected hosts , to optical estimates in [ sec : opt ] . finally , we compare the optical properties of the grb host galaxies to those of sub - mm and radio selected star - forming galaxies ( [ sec : comp ] ) .

all observations were undertaken months to years after the grb explosions to ensure negligible contamination from the afterglows . this possibly indicates that the stellar populations in the grb hosts are on average younger , supporting the massive stellar progenitor scenario for grbs , but it is also possible that grb hosts are on average less dusty . beyond the specific results presented in this paper , the sub - mm and radio observations serve as an observational proof - of - concept in anticipation of the upcoming launch of the swift grb mission and sirtf . these new facilities will possibly bring grb host galaxies into the forefront of star formation studies .

we present the first comprehensive search for submillimeter and radio emission from the host galaxies of twenty well - localized-ray bursts ( grbs ) . with the exception of a single source , all observations were undertaken months to years after the grb explosions to ensure negligible contamination from the afterglows . we detect the host galaxy of grb000418 in both the sub - mm and radio , and the host galaxy of grb000210 only in the sub - mm . these observations , in conjunction with the previous detections of the host galaxies of grb980703 and grb010222 , indicate that about of grb host galaxies are ultra - luminous ( l ) and have star formation rates of about m yr . as an ensemble , the non - detected hosts have a star formation rate of about m yr ( ) based on their radio emission . the detected and ensemble star formation rates exceed the optically - determined values by an order of magnitude , indicating significant dust obscuration . in the same vein , the ratio of bolometric dust luminosity to uv luminosity for the hosts detected in the sub - mm and radio ranges from , and follows the known trend of increasing obscuration with increasing bolometric luminosity . we also show that , both as a sample and individually , the grb host galaxies have bluer colors as compared with galaxies selected in the sub - mm in the same redshift range . this possibly indicates that the stellar populations in the grb hosts are on average younger , supporting the massive stellar progenitor scenario for grbs , but it is also possible that grb hosts are on average less dusty . beyond the specific results presented in this paper , the sub - mm and radio observations serve as an observational proof - of - concept in anticipation of the upcoming launch of the swift grb mission and sirtf . these new facilities will possibly bring grb host galaxies into the forefront of star formation studies .

astro-ph0210645

c

we presented the most comprehensive scuba , vla , and atca observations of grb host galaxies to date . the host galaxy of is the only source detected with high significance in both the sub - mm and radio , while the host galaxy of grb000210 is detected with @xmath255 in the sub - mm when we combine our observations with those of @xcite . when taken in conjunction with the previous detections of grb980703 in the radio @xcite and grb010222 in the sub - mm @xcite , these observations point to a @xmath256 detection rate in the radio / sub - mm . this detection rate confirms predictions for the number of sub - mm bright grb hosts , with @xmath257 mjy , based on current models of the star formation history assuming a large fraction of obscured star formation @xcite . the host galaxies detected in the sub - mm and radio have star formation rates from about @xmath258 to @xmath259 m@xmath3 yr@xmath5 , while statistically the non - detected sources have an _ average _ sfr of about @xmath6 m@xmath3 yr@xmath5 . these star formation rates exceed the optically - inferred values by over an order of magnitude , pointing to significant dust obscuration within the grb host galaxies detected in the sub - mm and radio , and possibly the sample as a whole . still , the optical afterglows of the bursts that exploded in the sub - mm / radio bright host galaxies did not suffer significant extinction , indicating that : ( i ) the grbs did not explode in regions where dust obscuration is significant , or ( ii ) the uv and x - ray emission from the afterglow destroys a significant amount of dust in the local vicinity of the burst . we have also shown that grb host galaxies , even those detected in the sub - mm / radio , have bluer @xmath9 colors compared to galaxies selected in the sub - mm or radio bands in the same redshift range . this is not the result of an observational bias against dusty galaxies in the grb host sample since the afterglows of grbs which exploded in the radio / sub - mm bright hosts were not significantly obscured . more likely , this is the result of younger stellar populations in these galaxies , or possibly a patchy dust distribution . if the reason is younger stellar population then this provides additional circumstantial evidence in favor of massive ( and hence short - lived ) stars as the likely progenitors of grbs . a potential bias of the grb host galaxy sample is that the popular `` collapsar '' model of grbs calls for high mass , low metallicity stellar progenitors @xcite . this may result in preferential selection of low metallicity ( and hence less dusty ) host galaxies . however , it appears that grb progenitors can even have solar metallicity , and that a very low metallicity is unfavored by the required initial conditions for a grb explosion . moreover , studies of the milky way ( see @xcite for a recent review ) , local galaxies ( e.g @xcite ) , and high-@xmath31 galaxies ( e.g. @xcite ) , indicate that there are considerable variations in metallicity within galaxies . this may be especially true if several independent episodes of star formation have occured within the galaxy . thus , even if there is a bias towards low metallicity for grb progenitors ( and hence their immediate environments ) it is not obvious that this introduces a bias in the host galaxy sample . nonetheless , while the observations presented in this paper clearly indicate the potential of grb selection of high-@xmath31 galaxies for the study of star formation , a much larger sample is required to complement existing optical and sub - mm surveys . this may become possible in the near future with the upcoming launch ( sep . 2003 ) of swift . with an anticipated rapid ( @xmath260 minute ) and accurate localization of about 150 bursts per year , the grb - selected sample will probably increase to several hundred galaxies over the next few years . the rapid localization would most likely result in a large fraction of redshift measurements thanks to the bright optical afterglows . in addition to the localization of a large number of grb hosts , the study of these galaxies ( as well as those in other samples ) would greatly benefit from the advent of new facilities , such as sirtf , alma , evla , and the ska . in figure [ fig : sirtf ] we again plot the rest - frame seds of arp220 and the sub - mm / radio bright grb hosts . overplotted on these seds are the @xmath32 sensitivities of sirtf , alma , and the evla for 200-sec exposures at redshifts 1 and 3 , as well as the sensitivities of current instruments ( vla and scuba ) . the contributions of these new facilities to star formation studies are threefold : ( i ) increased sensitivity , ( ii ) increased resolution , and ( iii ) increased frequency coverage . these improvements will serve to ameliorate the main limitations of present radio , sub - mm , and ir observations ( [ sec : intro ] ) , by allowing the detection of more representative star forming galaxies at high redshift , in addition to a better constraint on the total dust bolometric luminosity and accurate localizations , which would facilitate follow - ups at optical wavelengths . in conjunction with increasingly larger samples of galaxies selected in the optical , the radio / sub - mm / ir , and by grbs , the future of star formation studies is poised for great advances and new discoveries . we thank k. adelberger , a. blain , and a. shapley for helpful discussions , and g. moriarty - schieven for help with the data reduction . we also thank s. chapman for providing us with the optical / nir colors and redshifts of radio pre - selected sub - mm galaxies prior to publication . , j. r. 1982 , an introduction to error analysis . the study of uncertainties in physical measurements , : a series of books in physics , oxford : university press , and mill valley : university science books , 1982 ) . lclrrr grb970228 & 0.695 & nov . 1 , 2001 & @xmath261 & @xmath262 & + & & nov . 2 , 2001 & @xmath263 & @xmath264 & @xmath265 + grb970508 & 0.835 & sep . 9 , 2001 & @xmath266 & @xmath267 & + & & sep . 10 , 2001 & @xmath268 & @xmath269 & + & & sep . 12 , 2001 & @xmath270 & @xmath271 & @xmath272 + grb971214 & 3.418 & nov . 2 , 2001 & @xmath273 & @xmath274 & @xmath273 + grb980329 & & sep . 13 , 2001 & @xmath275 & @xmath276 & + & & oct . 29 , 2001 & @xmath277 & @xmath278 & @xmath279 + grb980613 & 1.096 & nov . 1 , 2001 & @xmath280 & @xmath281 & + & & nov . 2 , 2001 & @xmath282 & @xmath283 & + & & dec . 7 , 2001 & @xmath284 & @xmath285 & @xmath286 + grb980703 & 0.966 & sep . 10 , 2001 & @xmath287 & @xmath288 & + & & sep . 12 , 2001 & @xmath289 & @xmath290 & @xmath291 + grb991208 & 0.706 & dec . 6 , 2001 & @xmath292 & @xmath293 & + & & dec . 7 , 2001 & @xmath294 & @xmath295 & @xmath296 + grb991216 & 1.020 & oct . 31 , 2001 & @xmath297 & @xmath298 & + & & nov . 3 , 2001 & @xmath299 & @xmath300 & + & & nov . 4 , 2001 & @xmath301 & @xmath302 & @xmath303 + grb000210 & 0.846 & sep . 12 , 2001 & @xmath304 & @xmath305 & + & & sep . 13 , 2001 & @xmath306 & @xmath307 & + & & sep . 14 , 2001 & @xmath308 & @xmath309 & @xmath310 + grb000301c & 2.034 & dec . 29 , 2001 & @xmath311 & @xmath312 & + & & dec . 30 , 2001 & @xmath313 & @xmath314 & @xmath315 + grb000418 & 1.119 & oct . 30 , 2001 & @xmath316 & @xmath317 & + & & oct . 31 , 2001 & @xmath318 & @xmath319 & + & & nov . 1 , 2001 & @xmath320 & @xmath321 & @xmath322 + grb000911 & 1.058 & sep . 13 , 2001 & @xmath323 & @xmath324 & + & & sep . 14 , 2001 & @xmath325 & @xmath326 & + & & oct . 31 , 2001 & @xmath327 & @xmath328 & + & & nov . 3 , 2001 & @xmath329 & @xmath330 & + & & nov . 4 , 2001 & @xmath331 & @xmath332 & @xmath333 + grb011211 & 2.140 & dec . 29 , 2001 & @xmath334 & @xmath335 & + & & dec . 30 , 2001 & @xmath336 & @xmath337 & + & & dec . 31 , 2001 & @xmath338 & @xmath339 & @xmath340 lcclcr 0.1 in grb970828 & 0.958 & vla & jun . 47 , 2001 & 8.46 & @xmath341 + grb980329 & & vla & jul . 22 sep . 10 , 2001 & 8.46 & @xmath342 + grb980613 & 1.096 & vla & may 1826 , 2001 & 8.46 & @xmath343 + grb981226 & & vla & jul . 24 oct . 15 , 2001 & 8.46 & @xmath344 + grb991208 & 0.706 & vla & apr . 14 jul . 20 , 2001 & 8.46 & @xmath345 + grb991216 & 1.020 & vla & jun . 8 jul . 13 , 2001 & 8.46 & @xmath346 + grb000210 & 0.846 & vla & sep . 16 oct . 12 , 2001 & 8.46 & @xmath347 + grb000301c & 2.034 & vla & jun . 15 jul . 22 , 2001 & 8.46 & @xmath348 + grb000418 & 1.119 & vla & jan . 14 feb . 27 , 2002 & 1.43 & @xmath349 + & & vla & dec . 8 , 2001 jan . 10 , 2002 & 4.86 & @xmath350 + & & vla & may 28 jun . 3 , 2001 & 8.46 & @xmath351 + grb000911 & 1.058 & vla & mar . 21 apr . 2 , 2001 & 8.46 & @xmath352 + grb000926 & 2.037 & vla & jun . 11 jul . 12 , 2001 & 8.46 & @xmath353 + grb010222 & 1.477 & vla & sep . 29 oct . 13 , 2001 & 4.86 & @xmath354 + & & vla & jun . 24 aug . 27 , 2001 & 8.46 & @xmath355 + grb990510 & 1.619 & atca & apr . 28 , 2002 & 1.39 & @xmath356 + grb990705 & 0.840 & atca & apr . 2122 , 2002 & 1.39 & @xmath357 + grb000131 & 4.5 & atca & apr . 28 , 2002 & 1.39 & @xmath358 + grb000210 & 0.846 & atca & apr . 2728 , 2002 & 1.39 & @xmath359 lccc 0.1 in grb970228 & @xmath360 & & 1 + grb970508 & @xmath361 & & 1 + grb970828 & & @xmath362 & 1.2 + grb971214 & @xmath363 & & 3 + grb980329@xmath364 & @xmath365 & @xmath366 & + grb980613 & @xmath367 & @xmath368 & + grb980703 & @xmath361 & @xmath369 & 10 + grb981226@xmath370 & & @xmath371 & + grb990510 & & @xmath372 & + grb990705 & & @xmath373 & + grb991208 & @xmath374 & @xmath375 & 20 + grb991216 & @xmath376 & @xmath377 & + grb000131 & & @xmath378 & + grb000210 & @xmath379 & @xmath380 & 3 + grb000301c & @xmath381 & @xmath382 & + grb000418 & @xmath383 & @xmath384 & 55 + grb000911 & @xmath385 & @xmath386 & 2 + grb000926 & & @xmath387 & + grb010222 & @xmath388 & @xmath389 & 1.5 + grb011211 & @xmath390 & &

we present the first comprehensive search for submillimeter and radio emission from the host galaxies of twenty well - localized-ray bursts ( grbs ) . with the exception of a single source , we detect the host galaxy of grb000418 in both the sub - mm and radio , and the host galaxy of grb000210 only in the sub - mm . the non - detected hosts have a star formation rate of about m yr ( ) based on their radio emission . the detected and ensemble star formation rates exceed the optically - determined values by an order of magnitude , indicating significant dust obscuration . in the same vein , the ratio of bolometric dust luminosity to uv luminosity for the hosts detected in the sub - mm and radio ranges from , and follows the known trend of increasing obscuration with increasing bolometric luminosity . we also show that , both as a sample and individually , the grb host galaxies have bluer colors as compared with galaxies selected in the sub - mm in the same redshift range .

we present the first comprehensive search for submillimeter and radio emission from the host galaxies of twenty well - localized-ray bursts ( grbs ) . with the exception of a single source , all observations were undertaken months to years after the grb explosions to ensure negligible contamination from the afterglows . we detect the host galaxy of grb000418 in both the sub - mm and radio , and the host galaxy of grb000210 only in the sub - mm . these observations , in conjunction with the previous detections of the host galaxies of grb980703 and grb010222 , indicate that about of grb host galaxies are ultra - luminous ( l ) and have star formation rates of about m yr . as an ensemble , the non - detected hosts have a star formation rate of about m yr ( ) based on their radio emission . the detected and ensemble star formation rates exceed the optically - determined values by an order of magnitude , indicating significant dust obscuration . in the same vein , the ratio of bolometric dust luminosity to uv luminosity for the hosts detected in the sub - mm and radio ranges from , and follows the known trend of increasing obscuration with increasing bolometric luminosity . we also show that , both as a sample and individually , the grb host galaxies have bluer colors as compared with galaxies selected in the sub - mm in the same redshift range . this possibly indicates that the stellar populations in the grb hosts are on average younger , supporting the massive stellar progenitor scenario for grbs , but it is also possible that grb hosts are on average less dusty . beyond the specific results presented in this paper , the sub - mm and radio observations serve as an observational proof - of - concept in anticipation of the upcoming launch of the swift grb mission and sirtf . these new facilities will possibly bring grb host galaxies into the forefront of star formation studies .

astro-ph0308388

i

in this paper we present the results of an unbiased interferometric survey of the star forming disk of m33 in co(1@xmath2110 ) ; the observations were done using the bima array . the 50 pc linear resolution of our survey map is comparable to the size of most gmcs . we derive a catalog of gmcs for m33 complete down to 1.5 @xmath212 . from simple statistics , we expect that no more than 15 of the 148 sources listed in our catalog are spurious . we estimate that approximately 60 clouds with a total mass of @xmath213 have been falsely rejected from the catalog . the interferometer data were compared with single dish fields observed at the uaso 12 m telescope to estimate the effects of spatial filtering and masking on the catalog . our results generally agree with those of @xcite , but the greater spatial coverage and flux completeness of the bima survey leads , in some cases , to different physical inferences . from the survey data , we conclude the following : \1 . the total mass of gmcs in our catalog is @xmath214 . from a comparison of the interferometer and single dish data in selected fields , we estimate that the total molecular mass of the galaxy is @xmath215 , 2% of the atomic mass . gmcs with masses above our completeness limit are described by a power - law distribution with @xmath8 . the power - law index of gmcs in m33 is steeper than that in the milky way ( @xmath216 ) . we infer that there exists a low mass cutoff or a change in the index to @xmath217 2 between @xmath218 and @xmath219 . the cutoff or change in slope implies that gmcs in m33 form with a characteristic mass of @xmath220 . the surface density of molecular gas decreases exponentially in radius , with a scale length of @xmath221 kpc . the scale length agrees well with the surface brightness of h@xmath125 emission ( @xmath222 kpc ) implying a scaling between star formation and molecular gas surface density of sfr @xmath223 . based on the h@xmath125 luminosity of m33 , we estimate a star formation rate of 0.24 @xmath224 yr@xmath18 , implying a molecular gas depletion time of @xmath225 yr . this very short time is not unreasonable given the large reservoir of atomic gas available at all radii . the rotation curve of the galaxy derived from co emission is in excellent agreement with that of the . we find no evidence for large scale radial motions of molecular gas in the galaxy . giant molecular clouds are preferentially found on bright filaments where the column is approximately @xmath226 cm@xmath101 . regions with column densities @xmath228 cm@xmath101 are devoid of catalog gmcs . we estimate a gmc lifetime of 1020 myr based on the close association between gmcs and filaments . given the typical velocity difference of 8 km s@xmath18 , the clouds would drift away from the filaments on longer time scales . since the filamentary structure of the gas appears to be independent of the existence of nearby gmcs , we conclude that it is the filamentary structure that forms first . the fraction of gas that becomes molecular is then determined by some other parameter , such as hydrostatic pressure , that is inversely correlated with galactic radius . \8 . at least 40% of the h@xmath125 flux is associated with catalog gmcs . if the undetected molecular mass produces a proportional amount of h@xmath125 flux , at least 80% of the emission would arise from regions associated with gmcs . at least 2/3 of catalog gmcs are within 50 pc of an region , so it appears that gmcs spend less than 1/3 of their lifetime in a quiescent phase prior to the onset of star formation . clouds above the median mass spend less than 15% of their lifetime in the quiescent phase . regions above the 90th percentile in luminosity are nearly twice as likely to have a gmc within 50 pc as compared to the entire population . nearly all catalog gmcs are exterior to holes . clearly , holes do not result from conversion of atomic to molecular gas . gmcs and compact holes ( @xmath229 pc ) are clustered over separation scales of 60 300 pc . however , since many gmcs are not associated with holes , the holes probably play only a secondary role in gmc formation . gmcs 66 & 88 are the only gmcs interior to an hole ( ddh 28 ) ; they are highly blueshifted with respect to . gmcs 40 , 51 , 54 , 123 & 133 , located along the edge of ddh 28 , are also blueshifted with respect to . conceivably these clouds were formed by the impact of a high velocity cloud on the atomic disk . although the molecular disk shows a sharp decline in the number of gmcs beyond @xmath230 kpc , the h@xmath125 disk extends to @xmath231 kpc . this suggests that , for the outer disk , either dispersal times of gmcs are significantly shorter than for the inner disk or that there exists a large population of gmcs below our detection threshold . this work was partially supported by nsf grant ast-9981308 to the university of california . this research made extensive use of nasa s astrophysics data system ( ads ) and the nasa / ipac extragalactic database ( ned ) . er s work is supported in part by a nsf graduate fellowship . blitz , l. & shu , f. h. 1980 , , 238 , 148 , l. 1993 , in protostars and planets iii , 125161 blitz , l. , bazell , d. , & desert , f.x . 1990 , 352 , l13 boulesteix , j. , courtes , g. , laval , a. , monnet , g. , & petit , h. 1974 , , 37 , 33 cheng , k.p . , hintzen , p. , smith , e.p . , angione , r. , talbert , f. , collins , n. , stecher , t. 1996 , , 28 , 904 corbelli , e. 2003 , , 342 , 199 corbelli , e. & salucci , p. 2000 , , 311 , 441 dame , t. m. , elmegreen , b.g . , cohen , r.s . , & thaddeus , p. 2001 , , 305 , 892 dame , t. m. , hartmann , d. , & thaddeus , p. 2001 , , 547 , 792 deul , e. r. & den hartog , r. h. 1990 , , 229 , 362 ( ddh ) deul , e. r. , & van der hulst , j. m. 1987 , , 67 , 509 digel , s. w. , aprile , e. , hunter , s. d. , mukherjee , r. , & xu , f. 1999 , , 520 , 196 elmegreen , b. g. 1987 , , 312 , 626 elmegreen , b. g. 1990 , asp conf . ser . 12 : the evolution of the interstellar medium , 247 engargiola , g. & plambeck , r. l. 1998 , , 3357 , 508 fukui , y. , mizuno , n. , yamaguchi , r. , mizuno , a. , & onishi , t. 2001 , , 53 , l41 hartmann , l. , ballesteros - paredes , j. , & bergin , e. a. 2001 , , 562 , 852 heyer , m. h. , carpenter , j. m. , & snell , r. l. 2001 , , 551 , 852 hodge , p. w. , balsley , j. , wyder , t. k. , & skelton , b. p. 1999 , , 111 , 685 israel , f. p. & van der kruit , p. c. 1974 , , 32 , 363 issa , m. , maclaren , i. , & wolfendale , a. w. 1990 , , 352 , 132 kennicutt , r. c. 1998 , , 498 , 541 kennicutt , r. c. 1989 , , 344 , 685 kim , w. , ostriker , e. c. , & stone , j. m. 2002 , , 581 , 1080 klessen , r. s. , burkert , a. , & bate , m. r. 1998 , , 501 , l205 lee , m. g. , freedman , w. l. , & madore , b. f. 1993 , , 417 , 553 mckee , c. f. & ostriker , j. p. 1977 , , 218 , 148 mizuno , n. et al . 2001 , , 53 , 971 oort , j. h. 1954 , , 12 , 177 rosolowsky , e. , plambeck , r. , engargiola , g. , & blitz , l. 2003 , , accepted . ( paper ii ) sanders , d. b. , scoville , n. z. , & solomon , p. m. 1985 , , 289 , 373 savage , b. d. , drake , j. f. , budich , w. , & bohlin , r. c. 1977 , , 216 , 291 scoville , n. z. & hersh , k.1979 , , 229 , 578 solomon , p. m. , rivolo , a. r. , barrett , j. , & yahil , a. 1987 , , 319 , 730 strong , a. w. & mattox , j. r. 1996 , , 308 , l21 strong , a. w. et al . 1988 , , 207 , 1 stutzki , j. 1999 , plasma turbulence and energetic particles in astrophysics , proceedings of the international conference , cracow(poland ) , 5 - 10 september 1999 , eds . : micha ostrowski , reinhard schlickeiser , obserwatorium astronomiczne , uniwersytet jagiello ' nski , krak ' ow 1999 , p. 48 - 60 . , 48 tenorio - tagle , g. 1981 , , 94 , 338 thilker , d. 2003 , private communication . wilson , c. d. & scoville , n. 1989 , , 347 , 743 wilson , c. d. & scoville , n. 1990 , , 363 , 435 wilson , c. d. & scoville , n. 1991 , , 370 , 184 wilson , c. d. , scoville , n. , & rice , w. 1991 , , 101 , 1293 wong , t. & blitz , l.2002 , , 569 , 157 wyder , t. k. , hodge , p. w. , & skelton , b. p. 1997 , , 109 , 927

the diameter synthesized beam corresponds to a linear resolution of 50 pc , sufficient to distinguish individual giant molecular clouds ( gmcs ) . from these data we generated a catalog of 148 gmcs with an expectation that no more than 15 of the sources are spurious . single dish observations of co in selected fields imply that our survey detects% of the co flux , hence that the total molecular mass of m33 is , approximately 2% of the mass . , this steep function implies that the gmcs in m33 form with a characteristic mass of .

we present the first interferometricco ( ) map of the entire disk of m33 . the diameter synthesized beam corresponds to a linear resolution of 50 pc , sufficient to distinguish individual giant molecular clouds ( gmcs ) . from these data we generated a catalog of 148 gmcs with an expectation that no more than 15 of the sources are spurious . the catalog is complete down to gmc masses of and contains a total mass of . single dish observations of co in selected fields imply that our survey detects% of the co flux , hence that the total molecular mass of m33 is , approximately 2% of the mass . the gmcs in our catalog are confined largely to the central region ( kpc ) . they show a remarkable spatial and kinematic correlation with overdense filaments ; the geometry suggests that the formation of gmcs follows that of the filaments . the gmcs exhibit a mass spectrum , considerably steeper than that found in the milky way and in the lmc . combined with the total mass , this steep function implies that the gmcs in m33 form with a characteristic mass of . more than 2/3 of the gmcs have associated regions , implying that the gmcs have a short quiescent period . our results suggest the rapid assembly of molecular clouds from atomic gas , with prompt onset of massive star formation .

0904.0251

i

recent theoretical and observational studies have provided strong evidence suggesting a connection between supermassive black hole ( smbh ) growth and galaxy evolution ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) . to better understand this connection , we need more direct measurements of smbh masses across cosmological distances . unfortunately , measuring smbh masses directly with dynamical methods requires high angular resolution , so use of these methods is limited to relatively nearby sources . this resolution problem can be obviated by studying smbhs in type 1 active galactic nuclei ( agns ) . in this case , the technique of reverberation mapping @xcite may be applied to measure the smbh mass , as has been done for more than 3 dozen type 1 agns to date ( e.g. , see recent compilation by * ? ? ? reverberation mapping relies on time resolution rather than angular resolution , since it takes advantage of the presence of a time delay , @xmath7 , between continuum and emission line flux variations observed through spectroscopic monitoring . this time delay corresponds to the light travel time across the broad - line region ( blr ) , and thus measurements of @xmath7 provide an estimate of the size of the region , @xmath8 . because the blr gas is well within the sphere of influence of the black hole and studies have provided evidence for virialized motions within this region ( e.g. , * ? ? ? * and references therein ) , @xmath3 can be related to the mass of the smbh through the velocity dispersion of the blr gas . although stellar and gas dynamical modeling and reverberation mapping are invaluable for measuring smbh masses directly , these methods are observationally taxing , due to resolution requirements for dynamical methods and time requirements for reverberation mapping campaigns . it is currently impossible to measure smbh masses directly for large statistical samples of galaxies . however , these direct mass measurements have led to the discovery of scaling relationships that relate smbh mass to other galaxy or agn observables that can be used to investigate the connection between smbh mass and galaxy evolution . in particular , some relations show connections between properties of the smbh ( i.e. , its mass ) and global properties of the host galaxy . examples include the correlation between smbh mass and bulge / spheroid stellar velocity dispersion , i.e. the @xmath9@xmath10 relation for agns @xcite and quiescent galaxies @xcite , and the correlation between smbh mass and galaxy bulge luminosity @xcite . other relations connect various agn properties . one such relation is the correlation between black hole mass and optical luminosity @xcite , which relates directly to the accretion rates of agns . there is also a correlation between blr radius and agn luminosity , i.e. , the @xmath3@xmath4 relation @xcite , which has proven to be very powerful for making indirect smbh mass estimations from single - epoch spectra ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? these indirect mass estimates can then be related to other properties of the host galaxy through direct measurements or separate scaling relations . although scaling relations have become widely used for statistical studies , it is important to understand that the indirect mass estimates determined by these relations are only as reliable as the direct mass measurements used to calibrate them . therefore , establishing a secure calibration across a wide dynamic range in parameter space and better understanding any intrinsic scatter in these relations is essential . to accomplish this , we must continue to make new direct measurements as well as to check previous results that are , for one reason or another , suspect . ngc 4051 , an sab(rs)bc galaxy with a narrow - line seyfert 1 ( nls1 ) nucleus at redshift @xmath11 , is a case in point . measurements of the blr radius and optical luminosity @xcite place it above the @xmath3@xmath4 relation , i.e. , the blr radius is too large for its luminosity ( cf . figure 2 of * ? ? ? . it also appears to be accreting mass at a lower eddington rate than other nls1s ( cf . figure 16 of * ? ? ? these two anomalies together suggest that perhaps the blr radius has been overestimated by @xcite ; indeed an independent reverberation measurement of the blr radius in ngc 4051 by ( * ? ? ? * hereafter s03 ) is about half the value measured by ( * ? ? ? * hereafter p00 ) . furthermore , neither the p00 nor s03 data sets are particularly well sampled on short time scales , so neither set is suitable for detection of smaller time lags ( e.g. , @xmath1223 days ) . in addition , @xcite reports a tully - fisher distance to ngc 4051 that is @xmath150% larger than that inferred from its redshift ( i.e. , 15.2 mpc versus 10.0 mpc , respectively ) . this suggests that the luminosity derived in past studies from the redshift could be an underestimate and might also be a contributing factor to the placement of ngc 4051 above the @xmath3@xmath4 relation . in this work , we present an analysis of new , optical spectroscopic and photometric observations of ngc 4051 , which represent the first results from a densely sampled reverberation mapping campaign that began in early 2007 . the campaign spanned more than 4 months , during which time we consistently obtained multiple photometric observations per night and spectroscopic observations nearly every night from a combination of five different observatories around the globe . the immediate goal of this campaign is to remeasure the h@xmath0 reverberation lag measurements for several objects on the low - luminosity end of @xmath3@xmath4 scaling relationship with poorly determined reverberation lags and , consequently , poorly determined black hole masses . we will also add to the overall sample of reverberation mapped agns by measuring lags for new objects . another goal for this extensive collection of homogeneous data is to reconstruct the observed response of the h@xmath0 emission line to an outburst from the variable continuum source by modeling the response as a function of both line - of - sight velocity and light travel time , i.e. , a `` velocity delay map '' ( for a tutorial , see * ? ? ? creation of a velocity delay map will provide novel insight into the structure and kinematics of the blr . though we have not yet attempted to reconstruct a full velocity delay map , we present preliminary velocity - resolved lag measurements for ngc 4051 . complete results for ngc 4051 and other campaign targets will be presented in future work .

we present the first results from a high sampling rate , multi - month reverberation mapping campaign undertaken primarily at mdm observatory with supporting observations from telescopes around the world . the primary goal of this campaign was to obtain either new or improved h reverberation lag measurements for several relatively low luminosity agns . we also present a preliminary look at velocity - resolved h light curves and time delay measurements , although we are unable to reconstruct an unambiguous velocity - resolved reverberation signal .

we present the first results from a high sampling rate , multi - month reverberation mapping campaign undertaken primarily at mdm observatory with supporting observations from telescopes around the world . the primary goal of this campaign was to obtain either new or improved h reverberation lag measurements for several relatively low luminosity agns . we feature results for ngc 4051 here because , until now , this object has been a significant outlier from agn scaling relationships , e.g. , it was previously a outlier on the relationship between the broad - line region ( blr ) radius and the optical continuum luminosity the relationship . our new measurements of the lag time between variations in the continuum and h emission line made from spectroscopic monitoring of ngc 4051 lead to a measured blr radius of light days and black hole mass of . this radius is consistent with that expected from the relationship , based on the present luminosity of ngc 4051 and the most current calibration of the relation by . we also present a preliminary look at velocity - resolved h light curves and time delay measurements , although we are unable to reconstruct an unambiguous velocity - resolved reverberation signal .

0904.0251

r

our measured h@xmath0 lag of @xmath46 days from this work is consistent , within the errors , to the most recent results for this object by s03 , who measured a lag of @xmath47 days . it is not clear how meaningful a direct comparison might be , however , because s03 measured the time delay between variations in the @xmath16800 continuum flux density and the integrated h@xmath48 flux rather than between the @xmath15100 continuum and h@xmath0 . we also note that the median sampling rate of s03 was larger than our measured lag , suggesting to us that the s03 light curves are undersampled . furthermore , s03 only perform a cross correlation analysis based on the dcf method , which sacrifices time resolution . our new time delay measurements are inconsistent , however , with the previous measurement of @xmath49 days by @xcite using data from p00 . these differences are unlikely a luminosity effect , since the average luminosity states of ngc 4051 were similar during this and the p00 campaigns ( log@xmath50 = 41.82 and log@xmath50 = 41.87 , respectively ) that of the peterson et al . campaign as well . ] . therefore , we carefully re - examined the light curves used by p00 to better understand possible causes for the observed inconsistency . @xcite suggested that the cause for a similar inconsistency between lag measurements from two reverberation mapping campaigns of ngc 5548 @xcite was due to different continuum variability timescales observed in the separate campaigns : longer continuum variability timescales lead to larger lag measurements . however , this explanation is unlikely to be the cause for the current inconsistency between our measured lag and that of p00 because the prominent variability timescales observed in both the p00 and current continuum light curves are similar ( @xmath14050 days ) . instead , the simplest explanation for the inconsistency between our measured lag and that of p00 is random error . we investigated this possibility by performing monte carlo simulations using the `` subset 1 '' h@xmath0 and 5100 continuum flux light curves from p00 with the goal of estimating the likelihood that a lag of @xmath51 = 5.8 days would be measured , even if the actual blr radius of the h@xmath0 emission was 2.7 light days , as expected from the @xcite @xmath52@xmath4 relation for the average luminosity of ngc 4051 during this time period . in each simulation we created a simulated h@xmath0 light curve by convolving a modified continuum light curve with a transfer function that assumed a blr with a thin spherical shell geometry of radius 2.7 light days . the sampling was increased in the modified continuum light curve over that of the original subset 1 continuum light curve by interpolating between the actual points on a 0.5 day scale . noise was added to the flux of each interpolated point using a random gaussian deviate . the size of each deviate was based on the average uncertainty in flux of the closest ` real ' continuum point on each side of the interpolated point . the simulated emission - line light curve was then sampled identically to the original subset 1 h@xmath0 light curve . we cross correlated this new emission - line light curve with the original subset 1 continuum light curve to determine a reverberation lag . the simulation was repeated 10,000 times , and lags were measured similarly for each iteration . we found that the average lag recovered was 2.7 days ( reassuring , since this was our input radius ) . however , we were unable to reproduce even a single lag of 5.8 days . in fact , the largest lag our simulations recovered was 4.0 days . a couple of possibilites suggest themselves : * the blr has physically changed in the 11-year interval between the time of p00 s subset 1 and the time of our recent campaign . this is a physical possibility since the dynamical timescale of the blr in ngc 4051 is @xmath53 years . * the p00 data are undersampled and there are really unresolved variations occurring on timescales shorter than the typical sampling interval of 2.2 days in subset 1 , the best - sampled part of the p00 light curve . we have no particular reason to believe the former possibility . however , the latter is suggested by how p00 established the relative uncertainties of their fluxes , namely by assuming that there are no true variations on time scales shorter that the typical sampling time scales and that any differences between closely spaced measurements reflect random errors only , not true variability . the estimates of the relative flux errors in the p00 subset 1 based on comparing measurements separated by 2 days or less are about 3.2% for both the contiuum and the line . in our new data set , obtained with the same instrument , we find relative errors of about 1.4% and 2.1% in the continuum and the line , respectively , using the method described in section [ s : lightcurves ] . we conclude that the flux uncertainties of the p00 data were overestimated due to short timescale variability . proceeding with the assumption that the p00 light curves are undersampled , we isolated the portion of the light curves that has the highest sampling across the sharpest features . we made this selection in an attempt to avoid occurrences of undersampling more complex variability . from the initial light curve , reproduced in figure [ fig : p00lc ] , we removed the first 10 observations that exhibit a broad inflection in the flux with a poorly defined peak . we perform a cross correlation analysis on these shortened light curves and determine a shorter lag , @xmath54 days . this lag determination is consistent with both the expected radius of 2.7 light days from the @xmath52@xmath4 relation , the current results , and the results of s03 . if we continue with the assumption that the light curves of p00 are undersampled , and the p00 flux uncertainties are overestimated , their assigned uncertainties would act to decrease the significance of short timescale variability , likely attributing it to noise instead . if we impose the average continuum flux uncertainty measured from our current data set ( given above ) on the shortened p00 continuum light curve , we can further improve the precision of this revised lag measurement to @xmath55 days . we then conducted another simulation in which we applied the sampling rate from the p00 light curves to the light curves from this work . by undersampling our current light curves , we can determine the probability that undersampling could lead to an overestimated lag similar to that measured by p00 . this type of simulation can provide further evidence that the lag measured by p00 was an overestimate and a consequence of undersampling . at the same time , it could diminish the possibility that the discrepancy in lag measurements is due to a difference in the physical conditions or structure of the blr during the p00 campaign compared to the present . using the continuum and h@xmath0 light curves shown in figure [ fig : lc4cc ] as the starting point , we modified them similarly to the continuum light curve described for our first set of simulations ( i.e. , increasing the sampling by interpolating between data points and adding noise to these points with a gaussian deviate ) , but this time we interpolated both the continuum and emission line light curves from this work on a 0.1 day interval . we then drew sample light curves from this parent light curve with the same length and sampling pattern as the full p00 light curve shown in figure [ fig : p00lc ] . we applied the same cross - correlation analysis ( as described in section [ s : lagresults ] ) to measure lags from these sample light curves . the parent light curves cover a longer time span than the sample light curves and therefore allow for multiple iterations of sample light curves to be chosen from different subsets of the parent light curves . the first iteration of sample light curves are created from the subset of the parent light curves where the beginning points match up , but the ends of the parent light curves are discarded . we then build up multiple iterations by shifting the starting point of the sample light curve in time by one time step , i.e. , 0.1 day , across the parent light curves . in this way , we were able to build up 330 sample light curves , where in the last iteration , the sample light curves begin in the middle of the parent light curves , but both sets of light curves end at the same time . based on the cross correlation analysis from these 330 sample light curves , the probability of measuring @xmath565.0 days is 0.6% ( 2 out of 330 ) , and the probability of measuring @xmath573.5 days ( i.e , the lag we calculated above from only a portion of the p00 light curve ) is @xmath18% ( 25 out of 330 ) . we conclude that undersampling is at least a plausible explanation for the difference between the p00 results and those reported here .

we feature results for ngc 4051 here because , until now , this object has been a significant outlier from agn scaling relationships , e.g. , it was previously a outlier on the relationship between the broad - line region ( blr ) radius and the optical continuum luminosity the relationship . our new measurements of the lag time between variations in the continuum and h emission line made from spectroscopic monitoring of ngc 4051 lead to a measured blr radius of light days and black hole mass of . this radius is consistent with that expected from the relationship , based on the present luminosity of ngc 4051 and the most current calibration of the relation by .

we present the first results from a high sampling rate , multi - month reverberation mapping campaign undertaken primarily at mdm observatory with supporting observations from telescopes around the world . the primary goal of this campaign was to obtain either new or improved h reverberation lag measurements for several relatively low luminosity agns . we feature results for ngc 4051 here because , until now , this object has been a significant outlier from agn scaling relationships , e.g. , it was previously a outlier on the relationship between the broad - line region ( blr ) radius and the optical continuum luminosity the relationship . our new measurements of the lag time between variations in the continuum and h emission line made from spectroscopic monitoring of ngc 4051 lead to a measured blr radius of light days and black hole mass of . this radius is consistent with that expected from the relationship , based on the present luminosity of ngc 4051 and the most current calibration of the relation by . we also present a preliminary look at velocity - resolved h light curves and time delay measurements , although we are unable to reconstruct an unambiguous velocity - resolved reverberation signal .

astro-ph9709249

c

we have presented the geometric optics for refraction by an interstellar plasma lens , with specific application to a lens with gaussian profile of free electron column density . we have shown that the one - dimensional refractive properties of a lens can be characterized completely by two dimensionless parameters . the first parameter characterizes the refractive power of the lens and is @xmath206 where @xmath18 , @xmath69 , @xmath34 , and @xmath61 are the wavelength of observation , maximum free electron column density , distance from lens to observer , and size of the lens transverse to the line of sight , respectively . the second parameter characterizes the extent to which the lens effect is diminished by the intrinsic size of the source and is @xmath207 which is the relative angular size of the background source , @xmath49 , compared to the angular size of the lens as seen by the observer , @xmath67 . the effect of the plasma lens is to enhance or reduce the observed brightness of the background source due to focusing or spreading of ray bundles , and to change the apparent position of the background source due to refraction . the minimum brightness of the background source occurs directly on the lens axis . for a point source , @xmath208 , the on - axis brightness will be @xmath103 of its nominal ( unlensed ) brightness . on either side of the lens axis , at a distance determined by the value of @xmath0 , the background source will have a maximum intensity due to focusing of ray bundles . if @xmath209 , the focusing of ray bundles will become strong enough for ray paths to cross , and multiple imaging of the background source will occur . for the case of a gaussian lens profile , an observer located within a region of multiple imaging can see as many as three images of the background source , each with a different brightness and appearing to come from slightly different directions . the total brightness of the source , obtained by adding the brightness of the multiple images , will be greater than the nominal brightness of the source . separating the multiple imaging regions from the single image regions are caustic surfaces , on which two of the three multiple images blend together and , in the limit of geometrical optics , the observed brightness of the background source grows without bound . an observer passing from a single - image region through the multiple imaging regions and back to a single - image region can use the observed position of the caustics to determine the magnitude of the parameter @xmath0 . the separation between the _ inner _ caustics can also be used to constrain the diameter of the lens . the primary effect of increasing the angular size of the background source in relation to the angular size of the lens , i.e. , increasing @xmath68 , is to smooth out the light curve and reduce the observed amplitudes of maximum and minimum intensity . we have generated sample light curves from our model and compared them to extreme scattering events observed towards the extragalactic sources 0954@xmath1658 , [ sec:0954 + 658 ] , and 1741@xmath2038 , [ sec:1741 - 038 ] . these two sources were chosen because their eses have the highest quality data available and , in the case of 1741@xmath2038 , polarization observations also exist . in general we find reasonable agreement between the observed and modelled light curves at 2.25 ghz . we have far more difficulty recreating the 8.1 ghz light curves by utilizing only the appropriate wavelength scalings for @xmath0 and @xmath68 . the discrepancies between the modelled and observed light curves may result from some combination of substructure within the lens , an anisotropic lens shape , a lens which only grazes the source rather than passing completely over it , or unresolved substructure within the extragalactic sources . for 0954@xmath1658 we find it to be strongly lensed at 2.25 ghz . interpreting the light curve for this source is difficult because of uncertainties about the source s structure at the time of the . we favor an interpretation in which the lens passed over a component in the source s jet . the lens toward this source is probably associated with radio loop iii so that the lens was 0.15 kpc distant . the peak column density in the lens was 0.24 pc @xmath3 , its size was 0.38 au , the electron density within the lens is @xmath5 @xmath3 , and its mass was @xmath6 m@xmath7 . the lens also caused the source s position to wander by as much as 250 mas at 2.25 ghz , an easily detectable amount using phase - referenced vlbi observations or by measuring the relative positions between source components . for 1741@xmath2038 , the ese was caused by a weak lens . the lens toward this source is likely to be associated with radio loop i and at a distance of 0.13 kpc . the lens peak column density is @xmath4 pc @xmath3 , size is 0.065 au , density is 300 @xmath3 , and mass is @xmath8 m@xmath7 . from clegg et al.s ( 1996 ) upper limit on the change in faraday rotation towards 1741@xmath2038 during the ese , we place an upper limit of approximately 100 mg on the magnetic field within the lens . the angular position wander caused by this lens was only 0.4 mas at 2.25 ghz . an angular displacement of this magnitude would not have been detectable for 1741@xmath2038 ; many other sources that have undergone eses have more complicated structures than 1741@xmath2038 , however , and relative position shifts of this magnitude between lensed and unlensed components might be detectable in those sources . these lens parameters are comparable , within 50% , to those derived for the ese for psr b1937@xmath121 ( @xcite ) . @xmath210 pc @xmath3 and @xmath211 . ( they actually fit for two lenses , we quote the total electron column density through both lenses and the mean size of the two lenses . ) a key assumption of our plasma lens explanation for eses is that the lenses are discrete objects . the lens properties we have derived are consistent with this assumption . if we assume the plasma temperature within the lenses to be @xmath127 k , the pressure within the lenses is @xmath212@xmath213 k @xmath3 . these pressures are well in excess of the average ism pressure of roughly 4000 k @xmath3 ( @xcite ) . such lenses would be either highly transitory features or embedded in high - pressure environments . romani et al . ( 1987 ) suggest ionization fronts , cooling instabilities , or both associated with old supernova remnants as sites of lenses . we emphasize that the difficulties in interpreting the light curve for future eses could be ameliorated considerably by vlbi imaging of a source as soon as possible after , or indeed during , an . considerable angular displacements might also be detected with such observations . we thank j. cordes for guidance at the beginning of this project and the referee , d. gabuzda , for comments which helped us clarify a number of the points in this paper . a portion of this work was performed while tjwl held a national research council - nrl research associateship . basic research in astronomy at the naval research laboratory is supported by the office of naval research .

we present the geometrical optics for refraction of a distant background radio source by an interstellar plasma lens , with specific application to a lens with a gaussian profile of free electron column density . the refractive properties of the lens are specified completely by a dimensionless parameter , , which is a function of the wavelength of observation , the free electron column density through the lens , the lens - observer distance , and the diameter of the lens transverse to the line of sight . a lens passing between the observer and a background source , due to the relative motions of the observer , lens , and source , produces modulations in the light curve of the background source . the exact form of the light curve depends only upon the parameter and the relative angular sizes of the source and lens as seen by the observer . other effects due to lensing include the formation of caustic surfaces , upon which the apparent brightness of the background source becomes very large ; the possible creation of multiple images of the background source ; and angular position wander of the background source . we find general agreement between modelled and observed light curves at 2.25 ghz , but poor agreement at 8.1 ghz . the discrepancies between the modelled and observed light curves may result from some combination of substructure within the lens , an anisotropic lens shape , a lens which only grazes the source rather than passing completely over it , or unresolved substructure within the extragalactic sources . the inferred properties of the lens responsible for the scattering event toward 0954 ( 1741 ) are that it was 0.38 au ( 0.065 au ) in diameter , with a peak column density of 0.24 pc ( pc ) , an electron density within the lens of ( 300 ) , and a mass of m ( m ) . the angular position wander caused by the lens was 250 mas ( 0.4 mas ) at 2.25 ghz . in the case of 1741 , we can place an upper limit of only 100 mg on the magnetic field within the lens .

we present the geometrical optics for refraction of a distant background radio source by an interstellar plasma lens , with specific application to a lens with a gaussian profile of free electron column density . the refractive properties of the lens are specified completely by a dimensionless parameter , , which is a function of the wavelength of observation , the free electron column density through the lens , the lens - observer distance , and the diameter of the lens transverse to the line of sight . a lens passing between the observer and a background source , due to the relative motions of the observer , lens , and source , produces modulations in the light curve of the background source . because plasma lenses are diverging , the light curve displays a minimum in the background source s flux density , formed when the lens is on - axis , surrounded by enhancements above the nominal ( unlensed ) flux density . the exact form of the light curve depends only upon the parameter and the relative angular sizes of the source and lens as seen by the observer . other effects due to lensing include the formation of caustic surfaces , upon which the apparent brightness of the background source becomes very large ; the possible creation of multiple images of the background source ; and angular position wander of the background source . if caustics are formed , the separation of the outer caustics can be used to constrain , while the separation of the inner caustics can constrain the size of the lens . we apply our analysis to two sources which have undergone extreme scattering events : 0954 , a source for which we can identify multiple caustics in its light curve , and 1741 , for which polarization observations were obtained during and after the scattering event . we find general agreement between modelled and observed light curves at 2.25 ghz , but poor agreement at 8.1 ghz . the discrepancies between the modelled and observed light curves may result from some combination of substructure within the lens , an anisotropic lens shape , a lens which only grazes the source rather than passing completely over it , or unresolved substructure within the extragalactic sources . our analysis also allows us to place constraints on the physical characteristics of the lens . the inferred properties of the lens responsible for the scattering event toward 0954 ( 1741 ) are that it was 0.38 au ( 0.065 au ) in diameter , with a peak column density of 0.24 pc ( pc ) , an electron density within the lens of ( 300 ) , and a mass of m ( m ) . the angular position wander caused by the lens was 250 mas ( 0.4 mas ) at 2.25 ghz . in the case of 1741 , we can place an upper limit of only 100 mg on the magnetic field within the lens .

1602.05383

i

the connection between o(@xmath3 ) quantum - rotor ( qr ) and spin models on has proved very useful in the context of phase transitions @xcite . about three decades ago , hamer , kogut and susskind @xcite mapped o(@xmath3 ) heisenberg models onto the corresponding [ ( 1 + 1 ) spatial and time dimensions ] nonlinear - sigma or qr models . the critical behavior was then inferred using strong - coupling expansion ( high - temperature , , where @xmath4 is the spin coupling ) : a kosterlitz - thouless transition for the o(2 ) model and a prediction of critical points at zero coupling ( pad@xmath5 continued ) for both o(3 ) and o(4 ) models . on the other hand , by mapping o(3 ) antiferromagnetic ( af ) heisenberg chains onto nonlinear sigma models in the semiclassical weak - coupling limit , haldane @xcite suggested that the ground state ( gs ) of chains with integral spins are gapped , while those with half - integral spins are gapless . moreover , shankar and read @xcite precisely clarified the distinction between gapped af spin models , characterized by the @xmath6 = 0 _ mod _ 2@xmath7 topological term , and gapless models for which @xmath8 _ mod _ 2@xmath7 , including the connection of the latter with a laplacian minimally coupled to the monopole potential@xcite . following the above developments , sachdev and senthil @xcite have presented a quite general mean - field and renormalization - group analysis of quantum phase transitions in magnets with the aid of _ generalized _ qr models . in particular , they showed that , under certain conditions , one can establish a mapping of double - layer antiferromagnets onto quantum rotors which sheds intuitive light on the way in which a qr can be used as an effective representation of a pair of antiferromagnetically coupled spins . still in this context , a single - site mf approximation was used to study an effective hamiltonian for spin - one bosons in an optical lattice in the presence of a magnetic field @xcite . further , a qr description of the mott - insulator transition in the bose - hubbard model within a functional - integral approach has also been elaborated in order to include particle number fluctuation effects @xcite . in this work we focus our attention on the study of the gs phase diagram of generalized quantum rotors on the frustrated ab@xmath2 chain , which is depicted in . the quantum rotors at each site are constrained , through sufficiently high values of the coupling @xmath9 ( and the coupling @xmath10 of the quartic term in the angular momentum ) , to mostly retain states with the minimum value of the angular momentum , i.e. , @xmath11 , as the frustration parameter @xmath4 is varied , thus enabling us to make a direct comparison with the corresponding _ quantum _ spin-1/2 ab@xmath2 chains . we analyze two types of frustration , as illustrated in , and try to interpret the derived phase diagrams in light of the ones of previous works on frustrated quantum spin-1/2 chains with the ab@xmath2 topology @xcite . instead of attempting to formalize a specific ( and probably rather complex ) mapping between the rotor and the spin models , we have opted to treat the rotor chain numerically by using a cluster variational mf theory , supplemented with exact diagonalization ( ed ) via lanczos algorithm@xcite and density matrix renormalization group ( dmrg ) @xcite of finite - size spin-1/2 chains . with respect to spin systems , as a motivation on the experimental side , the compound azurite @xcite has been successfully explained by the distorted diamond chain model@xcite , i.e. , a system with three spin-1/2 magnetic sites per unit cell and frustrated ferrimagnetic state . also , along with the study on the effect of frustration@xcite , for @xmath12 this class of models shares its phenomenology and unit - cell topology with quasi - one - dimensional compounds , such as the line of trimer clusters present in copper phosphates@xcite and the organic ferrimagnet pnnbno@xcite . the modeling of the ferrimagnetic phase @xcite has been mainly undertaken in the context of other models such as hubbard@xcite , @xmath13@xcite , ising@xcite , classical@xcite and quantum heisenberg@xcite , including magnetic excitations @xcite , and the quantum spherical model@xcite . the occurrence of new phases induced by hole - doping of the electronic band@xcite has also been carried out . this paper is organized as follows . in the next section we describe our qr model and numerical methods , and include in appendix a a derivation of the matrix elements of the operators acting on the single - site hilbert space represented by monopole harmonics . in we use single - site variational mf theory to study the rotor models , for the two frustration cases , and discuss the shortcomings of this semiclassical approach . then in we adopt a multi - site ( two - unit cell ) variational mf hamiltonian , which provides a substantial improvement on the treatment of quantum fluctuation effects , particularly in connection with the case of frustrated interaction between quantum rotors on b sites at the same unit cell . here we treat the respective spin-1/2 systems by making use of ed and dmrg techniques in order to pave the way for a direct comparison between rotors and spins . finally we report our conclusions in .

we present the ground state phase diagram of quantum - rotor chains with competing interactions ( frustration ) calculated through cluster variational mean field approaches . we consider two interaction patterns , named f and f models , between the quantum - rotor momentum and position operators , which follow exchange patterns of known one - dimensional spin-1/2 systems with a ferrimagnetic state in their phase diagrams . the spin-1/2 f model is known as the diamond chain and is related to the azurite compound , while the spin-1/2 f model was recently shown to present a frustration - induced condensation of magnons . we provide a detailed comparison between the quantum - rotor phase diagrams , in single- and multi - site mean - field approaches , and known results for the spin-1/2 models , including exact diagonalization and density matrix renormalization group data for these systems , as well as phase diagrams of the associated classical models .

we present the ground state phase diagram of quantum - rotor chains with competing interactions ( frustration ) calculated through cluster variational mean field approaches . we consider two interaction patterns , named f and f models , between the quantum - rotor momentum and position operators , which follow exchange patterns of known one - dimensional spin-1/2 systems with a ferrimagnetic state in their phase diagrams . the spin-1/2 f model is known as the diamond chain and is related to the azurite compound , while the spin-1/2 f model was recently shown to present a frustration - induced condensation of magnons . we provide a detailed comparison between the quantum - rotor phase diagrams , in single- and multi - site mean - field approaches , and known results for the spin-1/2 models , including exact diagonalization and density matrix renormalization group data for these systems , as well as phase diagrams of the associated classical models .

0912.2748

i

we have presented the results of _ spitzer _ irs infrared 535 @xmath0 m low - resolution ( r @xmath2 100 ) spectroscopy of 17 nearby ulirgs at @xmath1 0.2 , optically classified as non - seyferts ( liners , hii - regions , and unclassified , i.e. , no optical agn signatures ) . optically elusive , but intrinsically luminous buried agns were searched for in these optically non - seyfert ulirgs , on the basis of the strengths of pah emission and silicate dust absorption features . we then combined these results with those of our previous studies of nearby ulirgs , using _ irs , to investigate the energetic importance of buried agns in a _ complete sample _ of optically non - seyfert ulirgs in the local universe at @xmath1 0.3 ( 85 sources altogether ) . we arrived at the following primary conclusions . 1 . among the 17 newly observed optically non - seyfert ulirgs , the signatures of important energy contributions from buried agns were found in eight sources . in these sources , the extinction - corrected intrinsic buried agn luminosities were estimated at up to @xmath210@xmath3l@xmath4 , accounting for a significant fraction ( 633% ) of the observed infrared luminosities of these ulirgs . 2 . by combining our new results with those of our previous studies @xcite , we found that buried agns are energetically important in 37 sources of the complete ulirg sample of 85 ( 37/85 = 44% ) , confirming previous suggestion that optically elusive , luminous buried agns are common in the ulirgs of the local universe . we investigated the fraction of detectable luminous buried agns by separating ulirgs with 10@xmath3l@xmath4 @xmath18 l@xmath5 @xmath8 10@xmath17l@xmath4 ( 54 sources ) and l@xmath5 @xmath16 10@xmath17l@xmath4 ( 31 sources ) . we found that luminous buried agns were much more common in the latter ulirgs ( 22/31 = 71% ) than in the former ulirgs ( 15/54 = 28% ) , confirming the previous arguments that buried agns become more energetically important with increasing galaxy infrared luminosity . 4 . given the higher fraction of optical seyferts ( optically identified agns ) in ulirgs with higher infrared luminosities , luminous agns are more common in ulirgs with l@xmath5 @xmath16 10@xmath17l@xmath4 than in ulirgs with 10@xmath3l@xmath4 @xmath18 l@xmath5 @xmath8 10@xmath17l@xmath4 . because the detection rate of both optically identified seyfert agns and optically elusive buried agns is substantially lower in galaxies with lower infrared luminosities ( l@xmath5 @xmath8 10@xmath3l@xmath4 ) , we can conclude that the energetic importance of agns increases with increasing galaxy infrared luminosity , suggesting that _ the agn - starburst connections are luminosity dependent_. this may be related to the widely - proposed agn feedback scenario for the galaxy downsizing phenomenon . this work is based on observations made with the spitzer space telescope , operated by the jet propulsion laboratory at california institute of technology , under a contract with nasa . support for this work was provided by nasa , and also by an award issued by jpl / caltech . we thank the anonymous referee for his / her valuable comments which help significantly improve the clarity of the arguments in this manuscript . is supported by grants - in - aid for scientific research ( 19740109 ) . r.m . acknowledges partial support from inaf and asi , through contract asi - inaf i/016/07/0 . this research made use of the simbad database , operated at cds , strasbourg , france , and the nasa / ipac extragalactic database ( ned ) , which is operated by the jet propulsion laboratory at california institute of technology , under a contract with nasa . arshakian , t. g. 2005 , a&a , 436 , 817 armus , l. , et al . 2007 , apj , 656 , 148 bower , r. g. , benson , a. j. , malbon , r. , helly , j. c. , frenk , c. s. , baugh , c. m. , cole , s. , & lacey , c. g. 2006 , mnras , 370 , 645 brandl , b. r. , et al . 2006 , apj , 653 , 1129 bundy , k. , ellis , r. s. 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& scoville , n. z. 1988a , apj , 325 , 74 sanders , d. b. , soifer , b. t. , elias , j. h. , neugebauer , g. , & matthews , k. 1988b , apj , 328 , l35 sellgren , k. 1981 , apj , 245 , 138 sijacki , d. , springel , v. , di matteo , t. , & hernquist , l. 2007 , mnras , 380 , 877 simpson , c. 2005 , mnras,360 , 565 smith , j. d. , et al . 2007 , apj , 656 , 770 soifer , b. t. et al . 2000 , aj , 119 , 509 soifer , b. t. et al . 2001 , aj , 122 , 1213 soifer , b. t. , neugebauer , g. , matthews , k. , egami , e. , & weinberger , a. j. 2002 , aj , 124 , 2980 tran , q. d. , et al . 2001 , apj , 552 , 527 veilleux , s. , kim , d. -c . , & sanders , d. b. 1999 , apj , 522 , 113 veilleux , s. , & osterbrock , d. e. 1987 , apjs , 63 , 295 veilleux , s. , et al . 2009 , apjs , 182 , 628 voit , g. m. 1992 , mnras , 258 , 841 werner , m. w. , et al . 2004 , apjs , 154 , 1 wu , y. , charmandaris , v. , hao , l. , brandl , b. r. , bernard - salas , j. , spoon , h. w. w. , & houck , j. r. 2006 , apj , 639 , 157 lcrrrrcrc iras 04074@xmath372801 & 0.153 & @xmath80.07 & 0.07 & 1.33 & 1.72 & 12.2 & 0.05 ( c ) & liner + iras 05020@xmath372941 & 0.154 & @xmath80.06 & 0.10 & 1.93 & 2.06 & 12.3 & 0.05 ( c ) & liner + iras 13106@xmath370922 & 0.174 & @xmath80.12 & @xmath80.06 & 1.24 & 1.89 & 12.3 & @xmath80.05 ( c ) & liner + iras 14121@xmath370126 & 0.151 & 0.06 & 0.11 & 1.39 & 2.07 & 12.3 & 0.08 ( c ) & liner + iras 21477 + 0502 & 0.171 & @xmath80.09 & 0.16 & 1.14 & 1.46 & 12.3 & 0.14 ( c ) & liner + iras 03209@xmath370806 & 0.166 & @xmath80.10 & @xmath80.13 & 1.00 & 1.69 & 12.2 & @xmath80.13 ( c ) & hii - region + iras 10594 + 3818 & 0.158 & @xmath80.09 & @xmath80.15 & 1.29 & 1.89 & 12.2 & @xmath80.12 ( c ) & hii - region + iras 12447 + 3721 & 0.158 & @xmath80.12 & 0.10 & 1.04 & 0.84 & 12.1 & 0.10 ( c ) & hii - region + iras 14202 + 2615 & 0.159 & 0.18 & 0.15 & 1.49 & 1.99 & 12.4 & 0.10 ( c ) & hii - region + iras 15043 + 5754 & 0.151 & @xmath80.12 & 0.07 & 1.02 & 1.50 & 12.1 & 0.07 ( c ) & hii - region + iras 22088@xmath371831 & 0.170 & @xmath80.09 & 0.07 & 1.73 & 1.73 & 12.4 & 0.04 ( c ) & hii - region + iras 02480@xmath373745 & 0.165 & @xmath80.05 & @xmath80.11 & 1.25 & 1.49 & 12.2 & @xmath80.09 ( c ) & unclassified + iras 08591 + 5248 & 0.158 & @xmath80.10 & @xmath80.16 & 1.01 & 1.53 & 12.2 & @xmath80.16 ( c ) & unclassified + iras 02021@xmath372103 & 0.116 & @xmath80.07 & 0.30 & 1.45 & 1.72 & 12.0 & 0.21 ( w ) & unclassified + iras 08474 + 1813 & 0.145 & @xmath80.10 & @xmath80.19 & 1.28 & 1.54 & 12.1 & @xmath80.15 ( c ) & unclassified + iras 14197 + 0813 & 0.131 & @xmath80.17 & @xmath80.19 & 1.10 & 1.66 & 12.0 & @xmath80.18 ( c ) & unclassified + iras 14485@xmath372434 & 0.148 & @xmath80.11 & @xmath80.15 & 1.02 & 1.05 & 12.1 & @xmath80.15 ( c ) & unclassified + lclcccc iras 04074@xmath372801 & 50008 & 2009 mar 8 & 480 & 480 & 240 & 240 + iras 05020@xmath372941 & 50008 & 2008 dec 5 & 240 & 240 & 240 & 240 + iras 13106@xmath370922 & 50008 & 2009 mar 6 & 480 & 480 & 240 & 240 + iras 14121@xmath370126 & 50008 & 2009 mar 5 & 240 & 240 & 240 & 240 + iras 21477 + 0502 & 50008 & 2008 dec 5 & 960 & 960 & 480 & 480 + iras 03209@xmath370806 & 50008 & 2009 mar 8 & 480 & 480 & 240 & 240 + iras 10594 + 3818 & 50008 & 2009 jan 11 , 15 & 960 & 960 & 480 & 480 + iras 12447 + 3721 & 50008 & 2009 jan 24 & 240 & 240 & 240 & 240 + iras 14202 + 2615 & 50008 & 2009 mar 3 , 2009 apr 2 & 480 & 480 & 480 & 480 + iras 15043 + 5754 & 50008 & 2009 feb 26 & 960 & 960 & 480 & 480 + iras 22088@xmath371831 & 50008 & 2008 dec 5 & 960 & 960 & 480 & 480 + iras 02480@xmath373745 & 50008 & 2009 jan 25 & 240 & 240 & 240 & 240 + iras 08591 + 5248 & 50008 & 2008 dec 9 & 240 & 240 & 240 & 240 + iras 02021@xmath372103 & 3187 + 50008 & 2005 jan 15 , 2009 jan 15 & 240 & 240 & 240 & 240 + iras 08474 + 1813 & 30407 & 2007 dec 5 & 168 & 168 & 180 & 180 + iras 14197 + 0813 & 3187 + 50008 & 2005 feb 13 , 2009 mar 3 & 240 & 240 & 240 & 240 + iras 14485@xmath372434 & 50008 & 2009 apr 6 & 240 & 240 & 240 & 240 + lccccccccc iras 04074@xmath372801 & 60 & 420 & 235 & 3.3 & 32.8 & 2.5 & 0.6 & 0.4 + iras 05020@xmath372941 & 130 & 605 & 330 & 7.0 & 47.1 & 4.2 & 0.9 & 0.5 + iras 13106@xmath370922 & 115 & 425 & 565 & 3.3 & 27.6 & 3.5 & 0.4 & 0.4 + iras 14121@xmath370126 & 270 & 635 & 345 & 11.9 & 38.2 & 7.8 & 1.7 & 1.2 + iras 21477 + 0502 & 235 & 575 & 185 & 7.4 & 24.2 & 5.4 & 1.0 & 0.7 + iras 03209@xmath370806 & 285 & 555 & 410 & 9.9 & 26.4 & 9.2 & 1.6 & 1.5 + iras 10594 + 3818 & 350 & 780 & 490 & 16.0 & 46.0 & 11.1 & 2.4 & 1.7 + iras 12447 + 3721 & 210 & 625 & 260 & 7.0 & 24.0 & 4.1 & 1.4 & 0.8 + iras 14202 + 2615 & 160 & 455 & 265 & 18.7 & 52.9 & 13.6 & 1.9 & 1.4 + iras 15043 + 5754 & 285 & 770 & 555 & 8.0 & 29.3 & 6.7 & 1.6 & 1.3 + iras 22088@xmath371831 & 90 & 455 & 195 & 3.0 & 23.6 & 2.3 & 0.3 & 0.3 + iras 02480@xmath373745 & 325 & 915 & 535 & 7.3 & 25.6 & 5.0 & 1.2 & 0.8 + iras 08591 + 5248 & 310 & 695 & 535 & 9.7 & 30.7 & 9.7 & 1.8 & 1.8 + iras 02021@xmath372103 & 285 & 490 & 275 & 5.5 & 13.0 & 4.2 & 1.4 & 1.0 + iras 08474 + 1813 & 170 & 985 & 285 & 2.2 & 13.1 & 1.4 & 0.4 & 0.3 + iras 14197 + 0813 & 305 & 565 & 325 & 3.8 & 11.4 & 3.7 & 0.9 & 0.9 + iras 14485@xmath372434 & 150 & 495 & 295 & 6.8 & 26.2 & 6.8 & 1.6 & 1.6 + lccc iras 04074@xmath372801 & 3.0 & 1.2 & 0.40 + iras 05020@xmath372941 & 2.4 & 0.9 & 0.38 + iras 13106@xmath370922 & 2.0 & 1.2 & 0.60 + iras 14121@xmath370126 & 1.3 & & + iras 21477 + 0502 & 0.8 & & + iras 03209@xmath370806 & 1.0 & & + iras 10594 + 3818 & 1.0 & & + iras 12447 + 3721 & 1.4 & 0.5 & 0.36 + iras 14202 + 2615 & 0.7 & & + iras 15043 + 5754 & 1.4 & 0.7 & 0.50 + iras 22088@xmath371831 & 2.6 & 1.0 & 0.38 + iras 02480@xmath373745 & 1.4 & 0.6 & 0.43 + iras 08591 + 5248 & 1.0 & & + iras 02021@xmath372103 & 1.4 & 0.4 & 0.29 + iras 08474 + 1813 & 2.0 & 1.0 & 0.50 + iras 14197 + 0813 & 0.8 & & + iras 14485@xmath372434 & 1.2 & & + lcc iras 04074@xmath372801 & 0.3 + iras 05020@xmath372941 & 0.4 + iras 13106@xmath370922 & 1.0 + iras 14121@xmath370126 & 0.8 + iras 21477 + 0502 & 0.6 + iras 22088@xmath371831 & 0.5 + iras 02480@xmath373745 & 0.9 + iras 08591 + 5248 & 0.5 + iras 14485@xmath372434 & 0.3 + lcccc iras 04074@xmath372801 & @xmath43 & x & @xmath43 & @xmath43 + iras 05020@xmath372941 & @xmath43 & x & @xmath43 & @xmath43 + iras 13106@xmath370922 & @xmath43 & x & @xmath43 & @xmath43 + iras 14121@xmath370126 & x & x & x & x + iras 21477 + 0502 & x & @xmath43 & x & @xmath43 + iras 03209@xmath370806 & x & x & x & x + iras 10594 + 3818 & x & x & x & x + iras 12447 + 3721 & x & x & x & x + iras 14202 + 2615 & @xmath43 & x & x & @xmath43 + iras 15043 + 5754 & x & x & x & x + iras 22088@xmath371831 & @xmath43 & @xmath43 & @xmath43 & @xmath43 + iras 02480@xmath373745 & x & x & x & x + iras 08591 + 5248 & x & x & x & x + iras 02021@xmath372103 & x & x & x & x + iras 08474 + 1813 & @xmath43 & x & @xmath43 & @xmath43 + iras 14197 + 0813 & x & x & x & x + iras 14485@xmath372434 & @xmath43 & x & x & @xmath43 + lcccc iras 04074@xmath372801 & 2 & 1 & 2 & 6 + iras 05020@xmath372941 & 1.5 & 2 & 3 & 8 + iras 13106@xmath370922 & 1 & 1 & 2.5 & 8 + iras 14202 + 2615 & 1 & 5.5 & 9.5 & 10 + iras 22088@xmath371831 & 1.5 & 1 & 1.5 & 10 + iras 08474 + 1813 & 0.3 & 0.7 & 1 & 5 + iras 14485@xmath372434 & 1 & 2 & 5 & 5 + llcc non - seyfert & total & 85 & 37 ( 44% ) + & l@xmath5 @xmath8 10@xmath17l@xmath4 & 54 & 15 ( 28% ) + & l@xmath5 @xmath16 10@xmath17l@xmath4 & 31 & 22 ( 71% ) + & @xmath39 0.15 & 52 & 18 ( 35% ) + & @xmath7 0.15 & 33 & 19 ( 58% ) + liner & total & 43 & 21 ( 49% ) + & l@xmath5 @xmath8 10@xmath17l@xmath4 & 25 & 9 ( 36% ) + & l@xmath5 @xmath16 10@xmath17l@xmath4 & 18 & 12 ( 67% ) + & @xmath39 0.15 & 28 & 10 ( 36% ) + & @xmath7 0.15 & 15 & 11 ( 73% ) + hii - region & total & 32 & 12 ( 38% ) + & l@xmath5 @xmath8 10@xmath17l@xmath4 & 22 & 4 ( 18% ) + & l@xmath5 @xmath16 10@xmath17l@xmath4 & 10 & 8 ( 80% ) + & @xmath39 0.15 & 20 & 6 ( 30% ) + & @xmath7 0.15 & 12 & 6 ( 50% ) + unclassified & total & 10 & 4 ( 40% ) + & l@xmath5 @xmath8 10@xmath17l@xmath4 & 7 & 2 ( 29% ) + & l@xmath5 @xmath16 10@xmath17l@xmath4 & 3 & 2 ( 67% ) + & @xmath39 0.15 & 4 & 2 ( 50% ) + & @xmath7 0.15 & 6 & 2 ( 33% ) +

we present the results of _ spitzer _ irs low - resolution infrared 535 m spectroscopy of 17 nearby ulirgs at 0.2 , optically classified as non - seyferts . the presence of optically elusive , but intrinsically luminous , buried agns is investigated , based on the strengths of polycyclic aromatic hydrocarbon emission and silicate dust absorption features detected in the spectra . the signatures of luminous buried agns , whose intrinsic luminosities range up tol , are found in eight sources . we combine these results with those of our previous research to investigate the energy function of buried agns in a complete sample of optically non - seyfert ulirgs in the local universe at 0.3 ( 85 sources ) . we confirm a trend that we previously discovered : that buried agns are more common in galaxies with higher infrared luminosities . because optical seyferts also show a similar trend , we argue more generally that the energetic importance of agns is intrinsically higher in more luminous galaxies , suggesting that the agn - starburst connections are luminosity - dependent .

we present the results of _ spitzer _ irs low - resolution infrared 535 m spectroscopy of 17 nearby ulirgs at 0.2 , optically classified as non - seyferts . the presence of optically elusive , but intrinsically luminous , buried agns is investigated , based on the strengths of polycyclic aromatic hydrocarbon emission and silicate dust absorption features detected in the spectra . the signatures of luminous buried agns , whose intrinsic luminosities range up tol , are found in eight sources . we combine these results with those of our previous research to investigate the energy function of buried agns in a complete sample of optically non - seyfert ulirgs in the local universe at 0.3 ( 85 sources ) . we confirm a trend that we previously discovered : that buried agns are more common in galaxies with higher infrared luminosities . because optical seyferts also show a similar trend , we argue more generally that the energetic importance of agns is intrinsically higher in more luminous galaxies , suggesting that the agn - starburst connections are luminosity - dependent . this may be related to the stronger agn feedback scenario in currently more massive galaxy systems , as a possible origin of the galaxy downsizing phenomenon .

astro-ph0510299

i

despite the recent extraordinary progress in observational cosmology and the successful convergence on a single cosmological model , galaxy formation and evolution largely remain an open issue . one critical aspect is how and when the present - day most massive galaxies ( e.g. elliptical galaxies and bulges with @xmath24 ) were built up and what type of evolution characterized their growth over cosmic time ( e.g. , cimatti 2004 ; glazebrook 2004 , and references therein ) . indeed , various current renditions of the @xmath25cdm hierarchical merging paradigm differ enormously in this respect , with some models predicting the virtually complete disappearance of such galaxies by @xmath26 ( e.g. , cole 2000 ; menci 2002 ; somerville 2004a ) and other models predicting a quite mild evolution , more in line with observations ( e.g. , nagamine 2001 ; 2005 ; granato 2004 ; somerville 2004b ; a direct comparison of such models can be found in fig . 9 of fontana 2004 ) . moreover , models that provide an acceptable fit to the galaxy stellar mass function at @xmath27 may differ considerably in the actual properties of the galaxies with @xmath24 at @xmath28 , with some models predicting very few , if any , passively evolving galaxies at these redshifts , at variance with recent findings ( cimatti 2004 ; mccarthy 2004 ; daddi 2005a ; saracco 2005 ) . while various @xmath25cdm models may agree with each other at @xmath22 ( where they all are tuned ) their dramatic divergence with increasing redshift gives us powerful leverage to restrict the choice among them , thus aiding understanding of the physics of galaxy formation and evolution . hence , a direct observational mapping of galaxy evolution through cosmic time is particularly important and rewarding , especially if a significant number of massive galaxies at @xmath29 can be identified and studied . in this regard , the critical questions concern the evolution with redshift of the number density of massive galaxies and their star formation histories , as reflected by their colors and spectral energy distributions ( seds ) . these questions have just started to be addressed by various spectroscopy projects , such as the k20 survey ( cimatti 2002a , 52 arcmin@xmath2 ) , the hubble deep fields ( hdfs ; ferguson 2000 , 5.3 arcmin@xmath2 in the hdf - north and 4.4 arcmin@xmath2 in the hdf - south ) , the great observatories origins deep survey ( goods ; giavalisco 2004 , 320 arcmin@xmath2 in the north and south fields combined ) the hst / acs ultra deep field ( s. beckwith 2006 , in preparation ; 12 arcmin@xmath2 ) , the gemini deep deep survey ( abraham 2004 , 121 arcmin@xmath2 ) , and the extension down to @xmath30 of the lyman break galaxy ( lbg ) project ( steidel 2004 , @xmath31 arcmin@xmath2 ) . however , massive galaxies are quite rare and likely highly clustered at all redshifts , and hence small areas such as those explored so far are subject to large cosmic variance ( daddi 2000 ; bell 2004 ; somerville 2004c ) . therefore , although these observation have demonstrated that old , passive and massive galaxies do exist in the field out to @xmath32 , it remains to be firmly established how their number and evolutionary properties evolve with redshift up to @xmath30 and beyond . to make a major step forward we are undertaking fairly deep , wide - field imaging with the suprime - cam on subaru of two fields of 940 arcmin@xmath2 each for part of which near - ir data are available from eso new technology telescope ( ntt ) observations . the extensive imaging has supported the spectroscopic follow - up with the vlt and the subaru telescopes , for which part of the data have already been secured . the prime aim of this survey is to understand how and when the present - day massive galaxies formed , and to this end , the imaging observations have been optimized for the use of optical / near - ir multi - color selection criteria to identify both star - forming and passive galaxies at @xmath33 . color criteria are quite efficient in singling out high redshift galaxies . the best - known example is the dropout technique for selecting lbgs ( steidel 1996 ) . besides targeting lbgs , color criteria have also been used to search for passively evolving galaxies at high redshifts , such as extremely red objects ( eros ) at redshifts @xmath34 ( thompson 1999 ; mccarthy 2004 ) and distant red galaxies ( drgs ) at redshifts @xmath35 ( franx 2003 ) . recently , using the highly complete spectroscopic redshift database of the k20 survey , daddi ( 2004a ) introduced a new criterion for obtaining virtually complete samples of galaxies in the redshift range @xmath36 , based on @xmath37 , @xmath38 and @xmath39 band for short ] imaging : star - forming galaxies are identified requiring @xmath40 ( for convenience , we use the term for galaxies selected in this way ) ; and passively evolving galaxies at @xmath41 requiring @xmath42 and @xmath43 ( hereafter ) . this criterion is reddening independent for star - forming galaxies in the selected redshift range , thus allowing us also to select the reddest most dust - extinguished galaxies , together with those that are old and passively evolving . this should allow for a relatively unbiased selection of @xmath19 galaxies within the magnitude limit of the samples studied . in this paper observations , data reduction and galaxy photometry are described , together with the first results on k - band selected samples of distant , high redshift massive galaxies . compared to optical , the near - ir selection ( in particular in the @xmath4 band ) offers several advantages , including the relative insensitivity of the k - corrections to galaxy type , even at high redshift , the less severe dust extinction effects , the weaker dependence on the instantaneous star formation activity , and a tighter correlation with the stellar mass of the galaxies . therefore , the study of faint galaxy samples selected in the near - infrared have long been recognized as ideal tools to study the process of mass assembly at high redshift ( broadhurst 1992 ; kauffmann & charlot 1998 ; cimatti 2002a ) . the paper is organized as follows : section 2 describes the observations and the data reduction . section 3 discusses the photometric calibration of the images . section 4 presents the selection and number counts for eros , , and . section 5 presents the analysis of the clustering of field galaxies , eros , , and . the properties of are presented in section 6 . finally , a brief summary is presented in section 7 . throughout the paper , we use the salpeter imf extending between 0.1 and 100 @xmath44 and a cosmology with @xmath45 , and @xmath46(km s@xmath47 mpc@xmath47)@xmath48 . for the sake of comparison with previous works , magnitudes and colors in both ab and vega systems have to be used . , @xmath49 , @xmath50 , and @xmath51 . ]

we accurately measure surface densities of arcmin and arcmin for the and the , respectively . both and are strongly clustered , at a level at least comparable to that of eros , with appearing more clustered than . we estimate the reddening , star formation rates ( sfrs ) and stellar masses ( ) for the ensemble of , confirming that to typical ( median ) values are , , and . follow - up optical and near infrared spectroscopy is in progress at the eso very large telescope ( vlt ) and at the subaru telescope , in order to elucidate more thoroughly the formation and evolution of massive galaxies .

we present the results of a deep , wide - area , optical and near - ir survey of massive high - redshift galaxies . the prime focus camera ( suprime - cam ) on the subaru telescope was used to obtain imaging over arcmin fields , while imaging was provided by the sofi camera at the new technology telescope ( ntt ) for a subset of the area , partly from the eso imaging survey ( eis ) . in this paper , we report on the properties of-band selected galaxies , identified from a total area of arcmin to , of which 320 arcmin are complete to . the selection technique was used to assemble complete samples of about 500 candidate massive star - forming galaxies ( ) and about 160 candidate massive passively evolving galaxies ( ) at ; and the color criterion was used to assemble a sample of about 850 extremely red objects ( eros ) . we accurately measure surface densities of arcmin and arcmin for the and the , respectively . both and are strongly clustered , at a level at least comparable to that of eros , with appearing more clustered than . we estimate the reddening , star formation rates ( sfrs ) and stellar masses ( ) for the ensemble of , confirming that to typical ( median ) values are , , and . a correlation is detected such that the most massive galaxies at are also the most actively star - forming , an effect that can be seen as a manifestation of _ downsizing _ at early epochs . the space density of massive at that we derive is 20%% that of similarly massive early - type galaxies at . adding this space density to that of our massive star forming class , , in the same redshift range produces a closer comparison with the local early - type galaxy population , naturally implying that we are detecting star formation in a sizable fraction of massive galaxies at , which has been quenched by the present day . follow - up optical and near infrared spectroscopy is in progress at the eso very large telescope ( vlt ) and at the subaru telescope , in order to elucidate more thoroughly the formation and evolution of massive galaxies .

astro-ph0510299

i

this paper presents the results of a survey based on @xmath93 photometry obtained by combining subaru optical and eso near - ir data over two separate fields ( deep3a - f and daddi - f ) . complete k - selected samples of galaxies were selected to @xmath84 in the deep3a - f over 320 arcmin@xmath2 , and to @xmath118 in the daddi - f over a field roughly twice the area . deep multicolor photometry in the @xmath254 bands were obtained for the objects in both fields . object catalogs constructed from these deep data contain more than @xmath255 objects in the nir bandpasses . galaxy @xmath4-band number counts were derived and found to be in excellent agreement with previous survey results . we have used color criteria to select candidate massive galaxies at high redshift , such as @xmath8-selected star - forming ( ) and passively evolving ( ) galaxies at @xmath9 , and eros , and derived their number counts . the main results can be summarized as follows . \1 . down to the @xmath4-band limit of the survey the log of the number counts of increases linearly with the @xmath4 magnitude , while that of flattens out by @xmath256 . over the deep3a - f we select 387 and 121 down to @xmath7 , roughly a factor of 10 more than over the 52 arcmin@xmath2 fields of the k20 survey . this corresponds to a @xmath257 higher surface density , quite possibly the result of cosmic variance . over daddi - f we select 108 and 48 down to @xmath258 . the clustering properties ( angular two - point correlation function ) of eros and @xmath8-selected galaxies ( both and ) are very similar , and their clustering amplitudes are about a factor of 10 higher than those of generic galaxies in the same magnitude range . the most strongly clustered populations at each redshift are likely to be connected to each other in evolutionary terms , and therefore the strong clustering of eros and bzks makes quite plausible an evolutionary link between bzks at @xmath30 and eros at @xmath34 , with star formation in subsiding by @xmath34 thus producing passively evolving eros . while some may well experience secondary , stochastic starbursts at lower redshift , the global evolutionary trend of the galaxy population is dominated by star formation being progressively quenched in massive galaxies , with the quenching epoch of galaxies depending on environmental density , being earlier in high - density regions . \3 . using approximate relations from daddi et al . ( 2004a ) and multicolor photometry , we estimated the color excess , sfr and stellar mass of . these @xmath203 galaxies have median reddening @xmath18 , average sfr@xmath259 , and typical stellar masses @xmath260 . correlations between physical quantities are detected : the most massive galaxies are those with the largest sfrs and optical reddening @xmath182 . the high sfrs and masses of these galaxies add further support to the notion that these @xmath261 star - forming galaxies are among the precursors of @xmath262 passive eros and @xmath263 early - type galaxies . the contribution to the total star formation rate density at @xmath19 was estimated for the @xmath84 in our fields . these vigorous starbursts produce an sfrd @xmath264 @xmath227 yr@xmath47 mpc@xmath228 , which is already comparable to the global sfrd at @xmath30 as estimated from other surveys and simulations ( e.g. springel & hernqwist 2003 ; heavens et al . 2004 ) . however , a sizable additional contribution is expected from @xmath265 . \5 . in a similar fashion , the stellar mass of was obtained , with the result that the number density of @xmath203 more massive than @xmath207 is about 20%@xmath1387% of that of similarly massive , early - type galaxies at @xmath221 , indicating that additional activity and subsequent quenching of star - formation in @xmath266 star - forming galaxies must account for increasing the number of massive passive galaxies by a factor of about 5 from @xmath267 . the number density of @xmath266 @xmath268s is similar to that of @xmath269s . given their strong star - formation activity , it seems that by @xmath1081.4 the full population of local @xmath266 passive galaxies could be eventually assembled as a result . this result , advocated also in daddi et al . ( 2005b ) , may appear in contradiction with the recent finding by bell et al . ( 2004 ) of a factor of 2 decrease in the number density of early - type galaxies at @xmath108 , with respect to the local value ( see also faber et al . 2005 ) . however , our analysis of the bell et al ( 2004 ) results shows that most of this evolution is to be ascribed to the progressive disappearence with increasing redshift of the fainter galaxies , while the population of the brightest , most massive galaxies being substantially stable . this would be , in fact , another manifestation of the _ downsizing _ effect . a future publication will address this point in its full details and implications . mapping the metamorphosis of active star - forming galaxies into passively evolving , early - type galaxies from high to low redshifts , and as a function of galaxy mass and environment is one of the primary goals of the main ongoing galaxy surveys . using subaru and vlt telescopes , optical and near - infrared spectra are being obtained , with targets from the present database having been selected according to the same criteria adopted in this paper . future papers in this series will present further scientific results from this _ pilot _ survey , along with a variety of data products . we thank the anonymous referee for useful and constructive comments that resulted in a significant improvement of this paper . the work is partly supported by a grant - in - aid for scientific research ( 16540223 ) by the japanese ministry of education , culture , sports , science and technology and the chinese national science foundation ( 10573014 ) . x.k . gratefully acknowledges financial support from the jsps . acknowledge support from nasa through the spitzer fellowship program , under award 1268429 . thanks the poincar fellowship program at observatoire de la cte dazur and the danish natural science research council for financial support .

we present the results of a deep , wide - area , optical and near - ir survey of massive high - redshift galaxies . the selection technique was used to assemble complete samples of about 500 candidate massive star - forming galaxies ( ) and about 160 candidate massive passively evolving galaxies ( ) at ; and the color criterion was used to assemble a sample of about 850 extremely red objects ( eros ) . the space density of massive at that we derive is 20%% that of similarly massive early - type galaxies at . adding this space density to that of our massive star forming class , , in the same redshift range produces a closer comparison with the local early - type galaxy population , naturally implying that we are detecting star formation in a sizable fraction of massive galaxies at , which has been quenched by the present day .

we present the results of a deep , wide - area , optical and near - ir survey of massive high - redshift galaxies . the prime focus camera ( suprime - cam ) on the subaru telescope was used to obtain imaging over arcmin fields , while imaging was provided by the sofi camera at the new technology telescope ( ntt ) for a subset of the area , partly from the eso imaging survey ( eis ) . in this paper , we report on the properties of-band selected galaxies , identified from a total area of arcmin to , of which 320 arcmin are complete to . the selection technique was used to assemble complete samples of about 500 candidate massive star - forming galaxies ( ) and about 160 candidate massive passively evolving galaxies ( ) at ; and the color criterion was used to assemble a sample of about 850 extremely red objects ( eros ) . we accurately measure surface densities of arcmin and arcmin for the and the , respectively . both and are strongly clustered , at a level at least comparable to that of eros , with appearing more clustered than . we estimate the reddening , star formation rates ( sfrs ) and stellar masses ( ) for the ensemble of , confirming that to typical ( median ) values are , , and . a correlation is detected such that the most massive galaxies at are also the most actively star - forming , an effect that can be seen as a manifestation of _ downsizing _ at early epochs . the space density of massive at that we derive is 20%% that of similarly massive early - type galaxies at . adding this space density to that of our massive star forming class , , in the same redshift range produces a closer comparison with the local early - type galaxy population , naturally implying that we are detecting star formation in a sizable fraction of massive galaxies at , which has been quenched by the present day . follow - up optical and near infrared spectroscopy is in progress at the eso very large telescope ( vlt ) and at the subaru telescope , in order to elucidate more thoroughly the formation and evolution of massive galaxies .

1301.5368

r

in assessing the many periods found in the period search , we used several criteria . first , periods identified using more than one technique were considered more robust detections . second , periods detected in both h@xmath1 and he i were of interest because of the possible wind - photosphere connection . third , we looked for sinusoidal modulation in the phase diagrams . finally , periods that were on the order of the rotational period of the star ( 13 - 18 d ; see sec . 7.2 below ) were of interest because they could indicate rotational modulation . some key results are listed in table 7 . lcccccclc [ ] 1998@xmath541999 & & 2.47 , 2.48 & & @xmath55 & & & & yes + & & 3.51@xmath543.62 & @xmath55 & & & @xmath55 & 5876 , 6566 & yes + & & 13.1@xmath5413.7 & @xmath55 & & & @xmath55 & 6562 & yes + & & 18.1 , 18.4 & & @xmath55 & & & & yes + 2000@xmath542001 & & 2.75 & & & @xmath55 & @xmath55 & 5877 & yes + & & 3.06 , 3.07 & @xmath55 & & & @xmath55 & 6564 & yes + & & 3.25 , 3.26 & & & & @xmath55 & 5876 , 6561 & yes + & & 6.39 & & @xmath55 & & & & yes + 2001@xmath542002 & & 4.38@xmath544.43 & @xmath55 & @xmath55 & & & & no + 2002@xmath542003 & & 4.24@xmath544.28 & @xmath55 & @xmath55 & & & & yes + & & 11.2 & @xmath55 & & & @xmath55 & 6563 & yes + 2004@xmath542005 & & 2.22 , 2.23 & & & @xmath55 & @xmath55 & 6567 & yes + & & 9.7 & & & & @xmath55 & 5876 , 6563 & yes + & & 19.1@xmath5419.5 & @xmath55 & @xmath55 & & @xmath55 & 5873 & yes + 2005@xmath542006 & & 2.23 , 2.24 & @xmath55 & & @xmath55 & & & yes + & & 2.60@xmath542.69 & @xmath55 & @xmath55 & & @xmath55 & 5878 & no + & & 4.32@xmath544.43 & @xmath55 & @xmath55 & & @xmath55 & 5876 , 6568 & yes many of the periods detected in our search were in the range with no obvious connection to rotational modulation . these periods may be associated with stellar pulsations or some type of evanescent events . in the he i @xmath26 data from 2000 - 2001 , a period of was identified in by both bayesian and clean periodograms , with sinusoidal modulation quite strong in both phase diagrams . a period was found in the he i @xmath26 data of the 1998 - 1999 season and periods of 6.01 and were detected in the he i @xmath26 data of the 2001 - 2002 season . in addition , a period was found in the 6565 bin of the 2005 - 2006 spectra . these periods are all similar to the period reported in spectra from 1998 by prinja et al . ( 2004 ) and may be due to a persistent or recurring phenomenon . many of the identified periods , especially those in the h@xmath1 equivalent width , showed harmonic modulation in their phase diagrams . this modulation is particularly associated with periods found in the h@xmath1 @xmath26 . given the scaling relation found by puls et al . ( 1996 ) between h@xmath1 @xmath26 and the mass - loss rate , it is tempting to conclude that the star s mass - loss rate is undergoing harmonic modulation , possibly due to stellar pulsations . however , caution is warranted in making any such connection . if the wind is translucent , the variable flux from pulsations at the surface may be modulating the ionization fraction of hydrogen , leading to changes in the h@xmath1 equivalent width . in the 2004 - 2005 season , a period of was found in the radial velocity data as well as in the 6567 bin of the 2d periodogram . this period was also detected in the h@xmath1 @xmath26 and radial velocity data in the 2005 - 2006 season . harmonic modulation was present in the phase diagrams for these periods . the fact that this period was found in back - to - back seasons implies that this may be a persistent or recurrent signal . indeed , in the 1998 - 1999 season a period of was detected in the radial velocity data and a period was found in the 6572 bin of the 2d periodogram . inspection of tables 4 - 7 reveals that periods of were detected in every season . sinusoidal modulation was evident in some of the phase diagrams for these periods . these periods were found in the equivalent width data as well as the 2d periodograms but not in the radial velocity data . it is interesting to note that the period may be an overtone of the periods . if these periods are separate detections of the same signal , it indicates a persistent or recurrent trend . from the 2d periodograms , we find that much of the variability in he i is detected near the central wavelength bin suggesting a photospheric origin . meanwhile , this same period may be detected in h@xmath1 but in a bin that implies an origin in the wind . for example , in 1998 - 1999 spectra a period of was found in the 5876 bin and a period of was found in the 6566 bin . in the 2005 - 2006 data , a period of was identified 5876 bin and a period of was found in the 6568 bin . the time scales of the periods can provide a hint as to the origin of the variability . a period due to rotational modulation of wind structure , such as a co - rotating interaction region ( cir ) , would be expected to be on the same time scale as the rotational period of the star . rotational modulation could also have time scales that are some fraction of the rotation period , if there were more than one wind structure present and they were approximately equally spaced . the dependence of the rotational period on the radius of the star is a major source of uncertainty . an accurate angular diameter measurement could help to constrain the stellar radius and the rotational period . the projected rotational velocity is another source of uncertainty since it is an upper limit , and a fraction of it may be due to macroturbuence rather than rotation . adopting a @xmath31 of 91 km s@xmath16 and a stellar radius of 32 r@xmath7 gives a maximum rotational period of @xmath5618 d. assuming a radius of 24 r@xmath7 with the same @xmath31 yields a maximum rotational period of @xmath5613 d. several of the detected periods fall within the range of estimated for the period of rotation . in the he i @xmath26 data from the 1998 - 1999 season periods of 18.1 and were found by the bayesian and clean periodograms , respectively . both phase diagrams exhibited sinusoidal modulation , particularly the period . a period of was detected in the radial velocity data from the same season . it is possible that these two periods have the same origin but with the period rooted in the photosphere while the period arises farther out in the wind . periods ranging from 19.1 to were identified in both the h@xmath1 and he i @xmath26 data for the 2004 - 2005 season . the phase diagrams for these periods all exhibit sinusoidal modulation . a period of was also found in the 5873 bin of the 2d periodogram the same season . the 5873 bin is in the wavelength region where we begin to see wind contamination in the he i line . also in this season , a period of was found in the central wavelength bins of 5876 and 6563 in the 2d periodograms . the period could be an overtone of the periods and may indicate a connection between the photosphere and wind emission . a period was also reported by prinja et al . ( 2004 ) in h@xmath1 , h@xmath17 , and he i @xmath26678 observations from 1998 .

a periodicity search was carried out on the equivalent width and radial velocity data , as well as on wavelength - binned spectra . , stellar pulsations may be the origin of some of the observed variability . periods on the order of the rotational period were also detected in the he i line in the 98 - 99 season and in both lines during the 04 - 05 season .

we present the results of a time - series analysis of 130 chelle spectra of ori ( b0 ia ) , acquired over seven observing seasons between 1998 and 2006 at ritter observatory . the equivalent widths of h ( net ) and he i were measured and radial velocities were obtained from the central absorption of he i . temporal variance spectra ( tvs ) revealed significant wind variability in both h and he i . the he i tvs have a double - peaked profile consistent with radial velocity oscillations . a periodicity search was carried out on the equivalent width and radial velocity data , as well as on wavelength - binned spectra . this analysis has revealed several periods in the variability with time scales of . many of these periods exhibit sinusoidal modulation in the associated phase diagrams . several of these periods were present in both h and he i , indicating a possible connection between the wind and the photosphere . due to the harmonic nature of these periods , stellar pulsations may be the origin of some of the observed variability . periods on the order of the rotational period were also detected in the he i line in the 98 - 99 season and in both lines during the 04 - 05 season . these periods may indicate rotational modulation due to structure in the wind .

1301.5368

i

the line profile variability of the h@xmath1 and he i @xmath25876 lines in the supergiant @xmath0 ori has been examined through time - series analysis of spectra from seven seasons of observations . this star has a strong and variable stellar wind , as demonstrated by its highly variable h@xmath1 line which is observed to have several profile morphologies including p cygni , inverse - p cygni , double absorption , and pure emission . profiles of the h@xmath1 line show net emission approximately 65% of the time . the he i line is primarily an absorption line with weak wind features in the wings of the line . the he i profile is seen to sway back and forth , possibly indicating pulsational radial velocity oscillations . temporal variance spectra were calculated for each season for both spectral lines . the tvs clearly show that both lines undergo significant variability extending beyond @xmath13@xmath57 region indicating the presence of wind variability . in both cases , the variability is greatest on the blue side of line center . the tvs for the he i line has a double - peaked profile indicative of radial velocity oscillations due to pulsations . the double peaks are contained within the @xmath57 region consistent with a photospheric or near photospheric origin for the radial velocity variations . the region of significant variability defined by the 99% confidence level of the tvs was used to set the wavelength regions over which equivalent width measurements were made for the h@xmath1 and he i spectra . radial velocity measurements were also made from the central absorption of the he i profile . a periodicity search was carried out on data from six of the seven seasons individually . a technique that applies bayesian statistics to the lomb - scargle periodogram was employed on the equivalent width , radial velocity , and binned - spectra time series . the clean algorithm was also used on the equivalent width time series . numerous periods were identified in the variability as a result of these analyses . all periods identified in the bayesian analysis had corresponding ls periodogram peaks that exceeded the 5% false alarm probability . phase diagrams were created for each identified period and a sinusoidal function was fit to the phased data . the resulting phase plots indicate that several of the periods are harmonic . periods on the order of the rotational period of the star ( 13 - 18 d ) were found in data from two seasons indicating possible rotational modulation . sinusoidal modulation was evident in the phase diagrams in both cases . in the 1998 - 1999 observing season , periods were detected in the he i equivalent width data . in the 2004 - 2005 h@xmath1 and he i equivalent width data , periods of 19.1 to were found . a period was also present in the 5876 and 6563 bins in the 2d periodograms from that season . this is a possible overtone of the period . most of the periods identified were in the range of . many of these periods were present in both h@xmath1 and he i data and exhibited sinusoidal patterns in their phase diagrams . stellar pulsations are a possible origin of this variability and provide evidence for a connection between the photospheric activity and the wind . particularly intriguing is the fact that periods of are present in every season and were found in both lines . this may represent a persistent mode of variability in this star . the spectral variability of @xmath0 ori is clearly complex and in need of further study . stellar pulsation modeling of this star is needed in order to determine if the periods reported here can be produced by radial or non - radial pulsations . observationally , a campaign to acquire simultaneous spectroscopic and photometric data could provide conclusive evidence for a connection between stellar pulsation and wind variability . a more complete time series at optical and uv wavelengths , probing the inner and outer wind regions , would provide a more complete picture of the wind variability . we wish to thank jon bjorkman , karen bjorkman , douglas gies , and thomas kvale , for their support and many excellent suggestions . this work was partially supported by an nsf - prest grant ( ast-0440784 ) awarded to nancy morrison and karen bjorkman . support for the acquisition of these spectra at ritter observatory came from : the university of toledo , the fund for astrophysical research , inc . , and the american astronomical society small research grants program . financial support for the publication of this work was received from the scott e. smith fund for research at ritter observatory and from adrian college . finally , thanks go to the following members of the ritter observing team for obtaining spectra of @xmath0 ori : nancy morrison , chris mulliss , david knauth , howard ritter , will fischer , karen bjorkman , anatoly miroshnichenko , john wisniewski , josh thomas , amanda gault , doug long , noel richardson , erica hesselbach , nick sperling , dan kittell , and ian mcginness . berghoefer , t.w . , baade , d. , schmitt , j. h. m. m. , et al . 1996 , , 306 , 899 blomme , r. , prinja , r. k. , runacres , m. c. , & colley , s. 2002 , , 382 , 921 boyajian , t.s . , gies , d.r . , barai , p. , et al . 2007 , , 119 , 742 bretthorst , g.l . , 2001a , in aip conf . 567 , bayesian inference and maximum entropy methods in science and engineering : 19th international workshop , ed . rychert , j. , erickson , g. & smith , c.r . 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the he i tvs have a double - peaked profile consistent with radial velocity oscillations . many of these periods exhibit sinusoidal modulation in the associated phase diagrams . several of these periods were present in both h and he i , indicating a possible connection between the wind and the photosphere . due to the harmonic nature of these periods

we present the results of a time - series analysis of 130 chelle spectra of ori ( b0 ia ) , acquired over seven observing seasons between 1998 and 2006 at ritter observatory . the equivalent widths of h ( net ) and he i were measured and radial velocities were obtained from the central absorption of he i . temporal variance spectra ( tvs ) revealed significant wind variability in both h and he i . the he i tvs have a double - peaked profile consistent with radial velocity oscillations . a periodicity search was carried out on the equivalent width and radial velocity data , as well as on wavelength - binned spectra . this analysis has revealed several periods in the variability with time scales of . many of these periods exhibit sinusoidal modulation in the associated phase diagrams . several of these periods were present in both h and he i , indicating a possible connection between the wind and the photosphere . due to the harmonic nature of these periods , stellar pulsations may be the origin of some of the observed variability . periods on the order of the rotational period were also detected in the he i line in the 98 - 99 season and in both lines during the 04 - 05 season . these periods may indicate rotational modulation due to structure in the wind .

1001.0750

r

one of the advantages of x - ray spectroscopy with high signal - to - noise characteristics is the availability of numerous line ratio diagnostics to assess conditions in the radiating plasma . in particular , he - like systems provide valuable diagnostic opportunity , as discussed extensively in the literature ( porquet et al . 2001 ; smith et al . 2001 ; and references therein ) . the g - ratio , defined as the flux ratio of the forbidden ( @xmath22 ) plus intercombination ( @xmath23 ) lines to the resonance ( @xmath24 ) line , is sensitive to the electron temperature ( @xmath0 ) , while the r - ratio ( flux ratio of the forbidden to intercombination lines ) is sensitive to @xmath1 . ratios of emission lines in the resonance line series ( transitions from 2p , 3p , etc . to ground , also known as he@xmath25 is the resonance line sometimes labeled @xmath26 or @xmath27 . ] , he@xmath28 , and so on ) are sensitive both to @xmath0 , through their relative boltzmann factors , and to the absorption by an intervening hydrogen column density ( @xmath2 ) through their energy separation . this analysis emphasizes the use of line ratio diagnostics , including those discussed above . we use the astrophysical plasma emission code ( apec ) with the atomic data in atomdb v1.3 ( smith et al . 2001 ) to calculate line emissivities , except for he - like , for which we use the more accurate calculations of chen et al . the model for absorption by gas with cosmic abundances is taken from morrison & mccammon ( 1983 ) . in this section we present the physical conditions of the emitting plasma as determined from the line ratios of specific he - like and other ions , in particular @xmath1 , @xmath0 , and @xmath2 . we use information determined from line ratios to constrain an empirical model of the emission measure distribution ( emd ) , and then allow additional parameters of the model to be constrained by global fits to the spectrum . we give the elemental abundances determined from these fits . finally we present velocity constraints from line centroids and widths . we use g - ratios from multiple ions to determine the electron temperature . figure 4 shows the observed g - ratios of he - like o , ne and mg , overplotted on their respective theoretical functions of @xmath0 . for comparison , the emissivities of their resonance lines peak at @xmath29 2 , 4 , and 6 mk , respectively , as shown in the figure . table 2 gives the derived @xmath0 from these ions . the g - ratio indicates that @xmath30 mk . the @xmath0 determination is highly reliable , given that recent theoretical calculations , which include the resonance contributions to the collisional excitation cross sections , agree with experimental measurements to within 7% ( chen et al . 2006 ; smith et al . 2009a , 2009b ) . on the other hand , the theoretical calculations for and have higher systematic uncertainties , and the observational errors are larger , such that the @xmath0 values derived from and carry less weight ( but are consistent with ) . both and are found far below their temperature of maximum emissivity @xmath31 , supporting an accretion shock scenario for their formation . lcc & 0.75@xmath170.13 & 2.4@xmath32 + & 0.98@xmath170.04 & 2.5@xmath33 + & 0.97@xmath170.19 & 2.1@xmath34 we use r - ratios from multiple ions to determine the electron density . figure 5 shows the observed r - ratios for , , and , overplotted on the theoretical functions of electron density @xmath1 from apec . table 3 presents the @xmath1 values derived from these r - ratios . sensitivity to @xmath0 is negligible near the observed r - ratio values . smith et al . ( 2009 ) show that the apec r - ratio for in the high density range is indistinguishable from the r - ratio calculated by chen et al . the theoretical r - ratios from apec for all three ions are in excellent agreement with porquet et al . ( 2001 ) over the density range reported here . lcc & 0.21@xmath170.07 & 5.7@xmath35 + & 0.51@xmath170.03 & 3.0@xmath36 + & 1.41@xmath170.34 & 5.8@xmath37 from we derive @xmath38 @xmath6 , while gives @xmath39 @xmath6 . the 3@xmath18 range from , between 2.5 and 3.9 @xmath40 @xmath6 , provides a tight constraint . 0.033 , quite close to the value of 0.446 @xmath17 0.124 reported by k02 . the difference of nearly a factor of 2 in the derived @xmath1 appears to be due to the difference in atomic data used , with their models possibly based on the raymond & smith code ( raymond 1988 ) . ] the best - fit value for , using all the lines in the region as described in section 2 , is @xmath41 @xmath6 . for comparison , we have also fit only the 3 lines of mg xi , again with line widths and relative positions fixed , obtaining @xmath42 7 @xmath17 2 @xmath40 @xmath6 , in good agreement with the best - fit value . this comparison suggests that line blending does not unduly affect the result . at low @xmath1 the population of the metastable @xmath43 level builds up since the decay rate is extremely low . at high @xmath1 electron impact excites the metastable level population up to the @xmath44 levels . in principle , low r - ratios may also be produced at low @xmath1 by photoexcitation . stelzer & schmitt ( 2004 ) and k02 dismiss photoexcitation based on the stellar temperature ( @xmath3 4000 k ) , but drake ( 2005 ) suggests that a hot spot above the stellar surface , where the accretion stream shocks , could produce sufficient photoexciting radiation . we have measured the flux at the excitation wavelengths 1647 , 1270 and 1034 for , , and , respectively , from the _ hubble space telescope _ stis ( herczeg et al . 2002 ) and the fuse spectra ( dupree et al . 2005 ) . the intensity at 1034 is an order of magnitude lower than at the longer wavelengths , constraining the black body temperature of the hot spot to be less than 10,000 k , in good agreement with _ international ultraviolet explorer _ analysis showing a blackbody at 7900 k covering about 5% of the stellar surface ( costa et al . 2000 ) . thus the ultraviolet measurements and the r - ratio rule out photoexcitation and support the interpretation of high @xmath1 . together with the temperature derived from the g - ratio , the density supports an accretion origin for . the ratio of @xmath1917.096 to @xmath1917.051 becomes sensitive to @xmath1 above @xmath8 @xmath6 ( mauche et al . . the measured ratio of 1.06 @xmath17 0.13 is at the low @xmath1 limit , ruling out the high density from this line ratio suggested by ness & schmitt ( 2005 ) . the hetg spectrum contains several series of resonance lines that indicate absorption by neutral gas along the line of sight . the most useful of these diagnostics are the and he@xmath25/he@xmath28 ratios because their formation temperatures are independently determined from the g - ratio . table 4 presents the observed line ratios , and their use as diagnostics for @xmath2 . figure 6 shows the theoretical he@xmath25/he@xmath28 ratios as functions of @xmath0 for and , for both unabsorbed and absorbed cases . the observed ratios are overplotted using @xmath0 determined from their g - ratios ( which , as noted above , is more reliable for than for ) . for the best - fit @xmath0 , gives @xmath45 @xmath46 and gives @xmath47 @xmath46 . these two values show a meaningful difference . for at 2.5 mk , the observed ratio is 11@xmath18 below the unabsorbed model , making the presence of an absorbing column quite definitive . the column density from is consistent with the lower limit of @xmath48 @xmath46 determined from the absence of and lines longward of 40 in the _ chandra _ letg spectrum ( raassen 2009 ) . lcrrrr he@xmath49/he@xmath50 & 6.54@xmath170.76 & 8.54 & 6.52 & 5.22 & 2.49 + ly@xmath49/ly@xmath50 & 6.95@xmath170.58 & 9.63 & 8.07 & 6.82 & 4.55 + he@xmath49/he@xmath50 & 7.38@xmath170.35 & 11.14 & 10.07 & 9.23 & 7.34 + ly@xmath49/ly@xmath50 & 8.24@xmath170.52 & 12.93 & 11.89 & 10.91 & 8.93 + ly@xmath49/ly@xmath50 & 8.24@xmath170.52 & 7.061 & 6.49 & 5.96 & 4.88 ratios of the h - like series lines ( ly@xmath51 , ly@xmath52 , etc . ) are also sensitive to both absorption and temperature , but unlike the he - like ions , h - like ions do not present an independent temperature diagnostic . if the absorption column depends on the ion , as implied by the inconsistency between and , then we need to assume a model @xmath0 to obtain a column density from the h - like line ratios . assuming 2.5 mk , the observed ratio ly@xmath25/ly@xmath28 indicates @xmath53 @xmath46 . this value is consistent within the errors with @xmath2 from and thus a third absorber is not required . for at 2.5 mk , the column density would be larger than the column density for , as shown in table 4 ; however , table 4 also shows that no absorption is required if the lines are formed at 10 mk . we must further consider the effects of temperature on line ratios . we can also estimate the temperature using the charge state balance . table 5 presents the he@xmath25/ly@xmath25 ratios for oxygen and neon . first , the observed ratios are corrected for different column densities as found above , and then @xmath0 is derived from the respective corrected ratios . for oxygen , good consistency is found for the temperatures derived from the g - ratio and the he@xmath51/ ly@xmath51 ratio , given a column density of about 8 @xmath54 @xmath46 . for neon , on the other hand , all the derived temperatures are larger than @xmath0 derived above from the g - ratio . thus it appears that some of the emission originates at higher temperature . using @xmath55 @xmath46 and @xmath56 mk , and the observed he@xmath51 flux , we predict the flux of the ne x ly@xmath51 to be only 18% of the observed value . in this case , the rest of the emission must be formed at higher temperature . if the trend of increasing @xmath2 with charge state continues , then @xmath2 for would be higher than @xmath57 @xmath46 , and the fraction of ne x formed at 2.5 mk would be somewhat larger . lcccc he@xmath49/ ly@xmath49 & 0.55@xmath170.052 & 0.70 & 0.85 & 1.67 + he@xmath49/ ly@xmath49 & 2.32@xmath170.08 & 2.48 & 2.60 & 3.04 + + identification & + + he@xmath49/ ly@xmath49 & 3.03 & 2.83 & 2.66 & 2.23 + he@xmath49/ ly@xmath49 & 4.16 & 4.08 & 4.01 & 3.87 the emissivity functions for lines of and both peak near 5 mk , suggesting the possibility of comparing their formation temperatures . the ratio of @xmath1915.014 to @xmath1915.261 is sensitive to @xmath0 , due to a blend of an inner shell excitation line of at 15.261 (brown et al . the temperature sensitivity essentially comes from the charge state balance of and . using the reported experimental dependence of the line ratio on the electron beam energy of the electron beam ion trap at lawrence livermore national laboratory ( brown et al . 2001 ) , the observed hetg value gives @xmath58 mk . despite similar peak temperatures , and are not formed together . apparently , the long tail of the ly@xmath51 emissivity function toward high temperature contributes significantly to its emission . the lines are predominantly formed in the accretion shock , while the lines are formed both in the shock and in the hotter corona . one might expect that the ions formed at low temperature ( , , and ) should all experience similar absorption . using @xmath2 derived from , we can derive characteristic emitting @xmath0 for and of 1.4 mk and @xmath59 mk , respectively . these temperatures are far lower than @xmath0 derived from the g - ratios . they are both also far lower than @xmath60 mk derived from the charge state ratio of oxygen represented over the range of @xmath2 found here , as shown in table 5 . we conclude that an increase in @xmath2 with increasing charge state ( presumably temperature ) up through is consistent with all the data . we note that argiroffi et al . ( 2009 ) claim evidence for resonance scattering of the strongest lines in the xmm - rgs spectrum of mp mus , though their rgs spectrum of tw hya is too weak to show the signatures of absorption we find here . we rule out resonance scattering in tw hya using the strong series of . an optical depth @xmath61 of about 0.4 for he@xmath51 would be required to model the observed he@xmath51/he@xmath52 ratio . for a single ion , the optical depth @xmath61 scales as @xmath62 , such that we can then predict the other line ratios . we find then that he@xmath51/he@xmath63 ratio is overpredicted by 50% . since the oscillator strengths decrease rapidly with increasing principal quantum number @xmath64 , only the he@xmath51 line might be affected by resonance scattering . we find instead , that all the lines are affected by absorption , and rule out resonance scattering as the absorption mechanism . we conclude that the absorber is neutral or near neutral , consistent with the preshock accreting gas , as suggested by theoretical studies . for example , lamzin ( 1999 ) considers the absorption by the preshock gas of the x - ray emitting plasma for different geometries and orientations . gregory et al . ( 2007 ) use realistic coronal magnetic fields coupled with a radiative transfer code to calculate the obscuration of x - ray emission by accretion columns , and suggest that this effect can explain the observed low x - ray luminosities of accreting young stars relative to non - accretors . we present here four models for the emission measure ( em ) distribution , where the factor 0.8 accounts for the hydgrogen to electron density ratio and the integral is taken over the volume @xmath65 . the intensity of a spectral feature @xmath66 em @xmath67 where @xmath68 is the emissivity in units of ph @xmath69 s@xmath14 and @xmath70 is the distance to the source . the function @xmath68 depends on @xmath0 , and is given in steps of log [ @xmath0 ( k ) ] = 0.1 in atomdb ( smith et al . 2001 ) . ] and elemental abundances ( table 6 ) . these models serve to illustrate how values derived from the line ratios affect the global fit to the spectrum and to show whether abundance determinations are robust . for all four models , the first - order heg and meg spectra are fit to a set of variable abundance apec models , using _ sherpa _ and applying different constraints to the fitted parameters . all models have acceptable goodness - of - fit values . model a has two @xmath0 components and a single absorber . model a should be appropriate for comparison with other x - ray spectra of cool stars obtained at lower spectral resolution . lccccc @xmath711 ( mk ) & 3.58@xmath170.04 & 2.5 & 2.5 & 2.5 + em1 ( @xmath72 @xmath6 ) & 1.11@xmath170.13 & 1.49@xmath170.09 & 1.56@xmath170.10 & 4.22@xmath170.70 + @xmath712 ( mk ) & 18.8@xmath170.5 & 11.2@xmath170.2 & 12.6 & 12.6 + em2 ( @xmath72 @xmath6 ) & 0.33@xmath170.01 & 0.47@xmath170.01 & 0.121@xmath170.004 & 0.101@xmath170.005 + @xmath2 ( @xmath73 @xmath46 ) & 0.15@xmath170.22 & 1.0 & 1.0 & 1.0 + n ( 8.05 ) & 0.66@xmath170.14 & 0.28@xmath170.06 & 0.53@xmath170.10 & 0.20@xmath170.04 + o ( 8.93 ) & 0.23@xmath170.02 & 0.14@xmath170.01 & 0.24@xmath170.02 & 0.09@xmath170.01 + ne ( 8.09 ) & 1.23@xmath170.08 & 2.04@xmath170.11 & 2.50@xmath170.13 & 1.04@xmath170.02 + mg ( 7.58 ) & 0.18@xmath170.02 & 0.16@xmath170.02 & 0.21@xmath170.02 & 0.18@xmath170.02 + si ( 7.55 ) & 0.33@xmath170.03 & 0.24@xmath170.02 & 0.29@xmath170.03 & 0.34@xmath170.03 + fe ( 7.67 ) & 0.13@xmath170.01 & 0.10@xmath170.01 & 0.20@xmath170.01 & 0.16@xmath170.01 model b is also a two-@xmath0 model , but with constraints imposed from the line ratios . the lower @xmath0 is fixed at 2.5 mk , and the single absorber @xmath2 is fixed at 1.0 @xmath74 @xmath46 ( a rough average of the values obtained from line ratios ) . the @xmath1-sensitive forbidden and intercombination line regions are excluded from the fit . table 6 also gives results from multicomponent models c and d , each with the low @xmath0 and a single @xmath2 fixed , as in model b. assuming that the hotter component is coronal in nature , a broad distribution of @xmath0 is reasonable , although the shape is not well constrained . we broaden the hot component using a gaussian - shaped function centered around 12.5 mk . for model c the entire spectrum is fit simultaneously , with only the forbidden and intercombination line regions excluded as for model b. for model d the emission measures for the two components are fit to line - free regions , identified visually and using apec models . the thermal continuum emission fit to line - free regions is strongly temperature - dependent and thus constrains the emission measure distribution . the abundances are then fit to narrow regions centered on the strong lines . these separate fitting procedures are iterated until the values stop changing . the resulting model d em distribution is shown in figure 7 . the larger statistical error for the low @xmath0 emission measure in model d compared with model c ( table 6 ) stems from the smaller number of bins used in the fits ; however , we expect the systematic errors for model d to be lower , given that we are only using bins whose information content is secure , and thus we choose model d to illustrate the model spectrum . by almost a factor of 2 . we attribute these difficulties primarily to the complexity of the absorption , and secondarily to the few constraints on the shape of the em distribution . ] figure 8 compares the model d spectra predicted by the broad `` coronal '' component and the soft `` accretion '' component with the observed spectra . table 1 lists the origin of each line as accretion or corona based on model d. an additional component with @xmath0 lower than 2.5 mk can be added to both models c and d but is not required , as it does not improve the fit significantly . similar results are obtained with somewhat different choices of width and peak @xmath0 for the hot component . since the line ratios indicate increasing @xmath2 with higher charge state , we tried adding a second absorber to the high @xmath0 gaussian component for models b , c , and d. robust solutions are difficult to obtain , as the absorption , abundances , and normalizations of the emission measures do not independently determine the global x - ray spectrum . we also explored the possibility that the low and high @xmath0 components have different metal abundances but again , without robust results . using @xmath0=2.5 mk , as derived from the line ratio , instead of @xmath0=3.58 mk as found in model a , has important implications for interpreting the formation of some of the emission lines . the ratio of the strong he@xmath51 and ly@xmath51 line emission drives the model a fit to more than 3.0 mk with very little absorption . specifically , only @xmath315% of the ly@xmath25 emission arises from the 2.5 mk component , whereas a 3.58 mk component can produce more than half of the emission . the 2.5 mk component produces essentially all of the , , , and emission and more than half the emission from . the fluxes from these lines formed at 2.5 mk show no increase over their average value during the flare , as shown in figure 1 , indicating that the flare is associated with the hotter corona rather than the accretion shock , and justifying its retention in our analysis . lines from , , ( fig . 1 ) , and are produced by the hotter component and may participate in the flare . while k02 found that was overpredicted by their model by a factor of about 3 , our models b , c , and d have no such problem . in fact , for models c and d , the small flux of the resonance line forces the emission measure to be negligible between @xmath33 and 5 mk ( fig . the relative elemental abundances given in table 6 are reasonably consistent for the different models . the abundances are also similar to those found by k02 , stelzer & schmitt ( 2004 ) , and drake et al . it is important to note that the continuum emission arises primarily from the hot component , except at the longest wavelengths ( fig . thus absolute abundances in the low @xmath0 component for ne , o , fe and other species can not be determined reliably . nevertheless , the extremely large ne / o abundance ratio appears to be a very robust result . differences in the absolute abundances derived here reflect both differences in @xmath0 and the degeneracy between emission measure and @xmath2 . for example , nitrogen and oxygen are formed entirely in the low temperature component and thus the abundance differences among the models reflect differences among the low temperature emission measure and @xmath2 , as does the difference in the neon abundance between models a and b. the difference in the neon abundance between models c and d also reflects the differences in their emission measures at 2.5 mk . weak emission is apparent from the s and ar complexes , but we have not included line fluxes from these elements in table 1 because the individual lines ( in particular the he - like resonance line ) can not not be cleanly determined in the four grating arms . instead we have used the model c global fit to obtain 0.21 @xmath17 0.09 and 1.41 @xmath17 0.49 times solar ( anders & grevesse 1989 ) for the s and ar abundances , respectively . a high ar / o abundance would add weight to drake et al.s ( 2005 ) suggestion that the accretion stream is depleted of grain - forming elements ; however , the high ar abundance is unfortunately not statistically significant . in this section , we discuss velocity constraints from the line measurements . the measurements of the emission line fluxes given in table 1 use gaussian lines in addition to the standard hetg calibration line spread function . table 7 gives the lines with the highest signal - to - noise ratios , for which gaussian widths are measured . lines not listed do not show statistically significant widths , but are consistent with the range of widths found here . for these fits the continuum level is allowed to vary to provide a better local fit . assuming the lines form in the same region , and using a flat continuum flux level from 13.45 to 13.75 , we force the 3 triplet lines to have the same gaussian width to improve the significance of the velocity measurement . figure 2 shows the best fit for the lines . as before , the centroids of the lines measured in each grating arm are fit independently . we thus obtain a velocity of 183 @xmath17 16 km s@xmath14 . the thermal doppler fwhm velocity for neon at 2.5 mk is 75 km s@xmath14 . the error in the calibration is estimated to be about 5% . thus we determine a turbulent velocity of 165 @xmath17 18 km s@xmath14 , including calibration error in quadrature with the 1@xmath18 statistical error . the line profiles are consistent with each other within the errors and suggest a range of velocities from zero up to about the sound speed of the gas ( 185 km s@xmath14 at 2.5 mk ) . the turbulent velocity is well below the preshock gas velocity of @xmath3500 km s@xmath14 . line centroids are consistent with reference wavelengths from atomdb to within the calibration uncertainty on the absolute wavelength scale . lrcccc & 10.239 & 0.0042 @xmath17 0.0030 & 122 @xmath17 87 & 75 & 96 + & 11.544 & 0.0024 @xmath17 0.0024 & 62 @xmath17 62 & 75 & 0 + & 12.134 & 0.0082 @xmath17 0.0009 & 203 @xmath17 23 & 75 & 189 + & 13.447 & 0.0103 @xmath17 0.0010 & 229 @xmath17 22 & 75 & 216 + & 13.553 & 0.0057 @xmath17 0.0014 & 126 @xmath17 32 & 75 & 101 + & 13.699 & 0.0073 @xmath17 0.0019 & 159 @xmath17 41 & 75 & 140 + & 15.014 & 0.0065 @xmath17 0.0040 & 129 @xmath17 80 & 45 & 121 + & 18.969 & 0.0074 @xmath17 0.0026 & 116 @xmath17 41 & 85 & 79 + we summarize here the physical conditions of the x - ray plasma from a consistent analysis of the spectra . the new diagnostic measurements strongly support k02 s argument that the low temperature x - ray component ( @xmath75 2.5 mk ) arises in the accretion shock . while the density we derive from , @xmath76 @xmath6 , is within the range found in active stars at higher @xmath0 ( @xmath3 6 mk ) , it is at least an order of magnitude larger than the few r - ratios reported ( huenemoerder et al . 2001 ; ness et al . 2002 ; osten et al . the @xmath1 derived from the r - ratio is also more than an order of magnitude larger than derived from in other cool stars ( see sanz - forcada et al . 2003 ; ness et al . 2004 ; testa et al . 2004 ) . we also measure the r - ratio and rule out photoexcitation , since the observed r - ratio can only be produced by high @xmath1 , namely @xmath77 @xmath6 . the g - ratios from , , and give similar @xmath78 mk , significantly lower than the @xmath0 of peak emissivity for ( 4 mk ) and ( 6.3 mk ) . the g - ratio from is particularly reliable because of good statistics and accurate atomic data . in our multi-@xmath0 models ( models c and d ) , this low @xmath0 component is isolated and does not connect continuously with the hotter , coronal component . active main - sequence stars tend to have emission measures rising up to 6 mk and above , such that , if biased at all , @xmath0-sensitive line ratios should be biased toward higher rather than lower temperature . thus the @xmath0 measurements also support the accretion shock scenario . more accurate g - ratio models for and are required to establish any @xmath0 differences among these ions . we also measure strong absorption using line ratios from several ions , and require at least two different absorbing column densities , with the higher charge states experiencing more absorption . it seems likely that the gap between the two components of the em distribution is caused by neutral h absorption of the soft x - ray spectrum that is produced by the hot coronal component . the pattern of absorption is reminiscent of the `` two - absorber x - ray sources '' reported by gdel et al . ( 2007b ) , where the coronal component has ten times more absorption than the soft component ; however , unlike tw hya , these sources have high accretion rates and are believed to drive jets . we note that the absorption in tw hya is identified here from line ratio diagnostics , whereas the absorption in gdel et al . ( 2007b ) was determined from ccd spectra . we were not able to determine multiple absorbers using standard global fitting methods , even with the high resolution spectrum presented here , because the continuum spectrum has low signal - to - noise ratio . on the other hand , it seems likely that with low spectral resolution , multiple absorbers could also be easily missed . thus the presence of more than one absorber may be a more universal characteristic than we can presently establish without reliable line ratio diagnostics . all the values of @xmath2 found here are higher than those found using the hydrogen ly@xmath49 profile , for which a conservative upper limit is @xmath79 @xmath46 ( herczeg et al . 2004 ) , indicating that the absorption is not due to the interstellar medium but is intrinsic to the stellar system . our column densities are consistent with the range of values previously reported from rosat and asca ( kastner et al . in fact the two different values from rosat and asca are consistent with our different values and may reflect the complex absorption coupled with the different instrument responses rather than time - variable absorption . as noted also by gdel et al . ( 2007b ) for the highly absorbed coronae of dg tau a , gv tau , dp tau , our x - ray measurements are higher than expected from the optical extinction assuming standard gas - to - dust ratios . for x - ray emission that is highly localized compared with the stellar ly@xmath25 , and preferentially absorbed by the accretion stream directly above it , a difference in @xmath2 derived by the two methods seems entirely reasonable .

the presence of , , and emission lines in the spectrum requires coronal structures at mk . lower temperature lines ( e.g. , from , , and ) formed at 2.5 mk appear more consistent with emission from an accretion shock . he - like line ratio diagnostics indicate thatmk and in the shock . these values agree well with standard magnetic accretion models .

we present x - ray spectral analysis of the accreting young star tw hydrae from a 489 ks observation using the _ chandra _ high energy transmission grating . the spectrum provides a rich set of diagnostics for electron temperature , electron density , hydrogen column density , relative elemental abundances and velocities and reveals its source in 3 distinct regions of the stellar atmosphere : the stellar corona , the accretion shock , and a very large extended volume of warm postshock plasma . the presence of , , and emission lines in the spectrum requires coronal structures at mk . lower temperature lines ( e.g. , from , , and ) formed at 2.5 mk appear more consistent with emission from an accretion shock . he - like line ratio diagnostics indicate thatmk and in the shock . these values agree well with standard magnetic accretion models . however , the _ chandra _ observations significantly diverge from current model predictions for the postshock plasma . this gas is expected to cool radiatively , producing as it flows into an increasingly dense stellar atmosphere . surprisingly , indicates , five times lower than in the accretion shock itself , and seven times lower than the model prediction . we estimate that the postshock region producing has roughly 300 times larger volume , and 30 times more emitting mass than the shock itself . apparently , the shocked plasma heats the surrounding stellar atmosphere to soft x - ray emitting temperatures and supplies this material to nearby large magnetic structures which may be closed magnetic loops or open magnetic field leading to mass outflow . our model explains the soft x - ray excess found in many accreting systems as well as the failure to observe high signatures in some stars . such accretion - fed coronae may be ubiquitous in the atmospheres of accreting young stars .

1001.0750

i

we have analyzed the deep _ chandra _ hetg spectrum of tw hya to assess the relative contributions of accretion and coronal emission . we summarize the most important of our findings : * the spectrum shows line and continuum emission from @xmath128 mk coronal plasma , which may have a broad emission measure distribution . unlike active main sequence stars , the coronal em distribution abruptly cuts off below @xmath129 mk , probably due to absorption by the accretion stream . * the spectrum also shows emission lines from plasma at @xmath130 mk , as predicted by standard models of the accretion shock . @xmath0 and @xmath1 diagnostics from he - like are in excellent agreement with accretion models for tw hya . * we measure the flux of the forbidden line in tw hya for the first time to better than 3@xmath18 , allowing a determination of electron density . this density is lower than @xmath1 from by a factor of four and lower than @xmath1 from the standard postshock cooling model by a factor of seven , and leads to a new model of an accretion - fed corona . * the high @xmath0 ions suggest a stellar corona . by contrast , line ratio diagnostics from the lower @xmath0 ions , indicate two regions with different densities . in our model , the accretion shock itself has @xmath131 mk and @xmath132 @xmath6 , while the postshock cooling region has @xmath133 mk and @xmath134 @xmath6 . the postshock plasma has 30 times more mass than the shock itself . the surface area filling factor of the shock is 1.5% while the postshock filling factor is approximately 6.8% . * line ratio diagnostics require at least two different absorbers , with higher column density ( @xmath2 ) for higher charge state . absorption by the accretion stream is larger by a factor of 2.5 for the shock than for the postshock region . * a range of models for the em distribution and elemental abundances provides acceptable fits to the global spectrum . while absorption , emission measure , and abundances are not independently determined by such methods , the high ne / o abundance seems to be a robust result . * from line profile analysis of lines we determine a subsonic turbulent velocity of about 165 km s@xmath14 . this high resolution x - ray spectrum of tw hya presents a rich set of diagnostic emission lines for characterizing the physical conditions of the high energy plasma and understanding the dominant physical processes . the observations strongly support the model of an accretion shock producing a few mk gas at high density , as first suggested by kastner et al . ( 2002 ) from an earlier hetg spectrum . the diagnostics also support the role of accretion in producing the soft x - ray excess at previously discovered ( gdel & telleschi 2007 ; robrade & schmitt 2007 ) . this excess emission requires that the accretion shock heat a large volume in the surrounding stellar atmosphere . in tw hya the filling factor at is larger than the filling factor of the shock at , and is consistent with the filling factors of the ultraviolet and optical continua . both open and closed magnetic field lines may emerge from this surrounding area to channel this ionized gas back into the corona . while it is not yet clear whether the energy from the impact of accretion at the star can heat a hot ( 10 mk ) corona , accelerate a highly ionized stellar wind , or drive hot jets , we suggest that accretion - fed coronae may be ubiquitous in accreting young stars . we acknowledge support from nasa to the smithsonian astrophysical observatory ( sao ) under _ chandra _ go7 - 8018x for gjml . nsb and sjw were supported by nasa contract nas8 - 03060 to sao for the chandra x - ray center . src s contribution to this work was supported by the sprague fund of the smithonian institution research endowment , and by nasa grant nng04ge77 g to sao . we thank randall smith for supporting the customized apec code runs . we thank the _ chandra _ mission planning team for their efforts to accommodate the ground - based observing campaign .

the spectrum provides a rich set of diagnostics for electron temperature , electron density , hydrogen column density , relative elemental abundances and velocities and reveals its source in 3 distinct regions of the stellar atmosphere : the stellar corona , the accretion shock , and a very large extended volume of warm postshock plasma . surprisingly , indicates , five times lower than in the accretion shock itself , and seven times lower than the model prediction . we estimate that the postshock region producing has roughly 300 times larger volume , and 30 times more emitting mass than the shock itself . such accretion - fed coronae may be ubiquitous in the atmospheres of accreting young stars .

we present x - ray spectral analysis of the accreting young star tw hydrae from a 489 ks observation using the _ chandra _ high energy transmission grating . the spectrum provides a rich set of diagnostics for electron temperature , electron density , hydrogen column density , relative elemental abundances and velocities and reveals its source in 3 distinct regions of the stellar atmosphere : the stellar corona , the accretion shock , and a very large extended volume of warm postshock plasma . the presence of , , and emission lines in the spectrum requires coronal structures at mk . lower temperature lines ( e.g. , from , , and ) formed at 2.5 mk appear more consistent with emission from an accretion shock . he - like line ratio diagnostics indicate thatmk and in the shock . these values agree well with standard magnetic accretion models . however , the _ chandra _ observations significantly diverge from current model predictions for the postshock plasma . this gas is expected to cool radiatively , producing as it flows into an increasingly dense stellar atmosphere . surprisingly , indicates , five times lower than in the accretion shock itself , and seven times lower than the model prediction . we estimate that the postshock region producing has roughly 300 times larger volume , and 30 times more emitting mass than the shock itself . apparently , the shocked plasma heats the surrounding stellar atmosphere to soft x - ray emitting temperatures and supplies this material to nearby large magnetic structures which may be closed magnetic loops or open magnetic field leading to mass outflow . our model explains the soft x - ray excess found in many accreting systems as well as the failure to observe high signatures in some stars . such accretion - fed coronae may be ubiquitous in the atmospheres of accreting young stars .

astro-ph0307322

c

the measured angular momenta are significantly less than expected from simple theories of cloud formation . in the absence of external forces , the angular momentum of a molecular cloud should be equal to the angular momentum of the gas from which it formed . in a shearing galactic disk , the initial angular momentum for a forming cloud is ( see appendix [ angder ] ) : @xmath230 in this equation , @xmath231 is the distance from the center of the galaxy , @xmath232 is galactocentric radius where the cloud is found , and @xmath233 is the galactic rotation curve ( from * ? ? ? * ) . the radial accumulation length @xmath234 is half the radial extent of the parent atomic gas . the radial mass distribution of the collapsing gas determines the parameter @xmath235 . in the simplest case , the radial accumulation length is set by requiring the mass of atomic hydrogen in a cylinder stretching to infinity in the @xmath236 direction and of radius @xmath234 to equal the mass of the molecular cloud : @xmath237 . we adopt @xmath238 in equation [ jgal ] calculated for the collapse of a cylinder . using the measured masses of molecular clouds and the local value of @xmath239 , we find that _ in all but 3 of the 36 resolved molecular clouds , the predicted angular momentum is higher than the observed value , on average by a factor of 5_. we calculated the values of @xmath239 using the maps of @xcite after recalibrating this map to match the surface density of @xcite . if the velocity gradients are due to turbulence instead of rotation , bb00 argue that the observed angular momentum should be scaled down by a factor of 2 to 3 , which only increases the discrepancy between the predicted angular momentum and the observed value . statistically , projection effects can account for only 20% of the discrepancy . we refine this simple model as follows : ( 1 ) by assuming that the gas far from the galactic plane does not contribute to the forming molecular cloud and ( 2 ) by including some estimate of projection effects . instead of the progenitor material extending infinitely far from the galactic plane , we assume the gas is accumulated over a cylinder with its height equal to its diameter , centered on the location of the gmc . the three - dimensional distribution of atomic hydrogen is unknown , but we assume a scale height of @xmath240100 pc throughout the galaxy with @xmath241 . changing this value by a factor of 2 does not alter the results significantly . again , the dimensions of the cylinder are determined by requiring its volume to contain a mass of atomic gas equal to that of the molecular cloud . using the radius of the cylinder as the radial accumulation length @xmath234 , the predicted angular momentum is determined from equation [ jgal ] . we also assume the clouds are solid body rotators with random orientations and scale the predicted angular momentum down by a factor of @xmath242 . if , instead , we assume the clouds are strictly aligned with the galaxy , the correction only differs from @xmath243 by 3% . we compare this model to the measurements in figure [ spangcomp ] . the measured angular momenta are plotted as @xmath244 error bars as a function of galactic radius . figure [ spangcomp ] shows that the observations are always less than the predictions of this solid body model ( filled circles ) . the discrepancy is more than an order of magnitude for 20 of the clouds . recent work on star formation at galactic scales suggests that star formation preferentially occurs where the gas disk is toomre unstable @xcite . we calculate the radial accumulation length if the clouds actually formed from the instability . the @xcite instability is a gravitational instability in a shearing , thin fluid disk that bunches the gas into concentric rings , provided the disk is unstable according to the criterion @xmath245 where @xmath246 is the local epicyclic frequency , @xmath247 is the ( three dimensional ) velocity dispersion of the fluid , and @xmath248 is the local surface mass density of the fluid under consideration . the radial accumulation length is set by the original radial extent of the contracting rings : @xmath249 where @xmath250 is the most unstable scale for toomre collapse . the rotation curve determines the epicyclic frequency for the galaxy @xmath251 we assume that there is sufficient mass in the annulus to form molecular clouds which is true over most of the galaxy . figure [ spangcomp ] also shows the predicted values of the cloud angular momentum for gmcs formed using the toomre instability . these values only agree with the observed angular momenta for a few clouds in the inner 500 pc of the galaxy , _ where the disk is most stable _ according to the criterion in equation [ toom_eq ] . since all but two of the clouds disagree with the predictions of the toomre instability by a large margin , it seems unlikely that the clouds form by the action of this instability alone . moreover , the toomre instability predicts that cloud angular momentum should increase with galactocentric radius , which is not seen in figure [ spangcomp ] . the parker instability is another potential avenue of molecular cloud formation @xcite . the parker instability is a magneto - hydrodynamic ( mhd ) effect in gas coupled to a buoyant magnetic field . as the instability evolves , a section of the field bulges out of the plane of the galaxy , causing the atomic gas to flow down the gravitational potential well along the edge of the bulge and collect into molecular clouds . the characteristic length scale of the instability is @xmath252 , where @xmath253 is the scale height @xcite . the values for the predicted angular momentum are shown in figure [ spangcomp ] , for a 100 pc scale height . these values have been corrected for the pitch angle of the magnetic field ( @xmath254 , * ? ? ? * ) since the collapse occurs along the magnetic field lines , so that @xmath255 . the parker instability also gives a large discrepancy between the observed and predicted values . matching the observed values would require a gas scale height of @xmath256 pc , which would imply an unrealistically large stellar mass density . we conclude _ none of the simple theories produce the observed values of angular momentum in the molecular clouds_. figure [ spangcomp ] compares the theoretical and observed angular momentum for the resolved molecular clouds . even using the moment based measurement of angular momentum ( @xmath47 ) , we find an average discrepancy of more than a factor of 5 between observation and theory . this discrepancy shows that nearly all clouds suffer an angular momentum problem independent of assuming solid - body rotation . the failure of the solid body model is particularly troubling since this model gives the minimum accumulation length required to gather the mass of the gmc from the atomic hydrogen . this constraint will limit even the most sophisticated models of cloud formation . there are at least two possible solutions to the angular momentum problem . one is to gather material for molecular clouds from similar galactocentric radii , thereby minimizing the shear in the atomic gas , as may happen in the swing amplification instability @xcite . if clouds have small radial accumulation lengths , they must have long azimuthal accumulation lengths . agreement with the observed angular momenta requires @xmath257 pc . to form a cloud of @xmath258 out of atomic hydrogen with a typical surface density of @xmath259 pc@xmath3 requires azimuthal accumulation lengths of @xmath260500 pc . with the maximum non - circular velocities in the atomic gas @xmath261 10 km s@xmath12 @xcite , this implies a limit on the timescale of cloud formation of @xmath262 myr , larger than the 1020 myr cloud lifetimes implied in paper i. this timescale is a significant fraction of the time between the spiral arm crossings for most of the galaxy away from the co - rotation radius @xcite . consequently , such a long time scale for cloud formation has difficulties explaining preferentially finding clouds in spiral arms of galaxies . a second solution is to brake the material with external forces such as magnetic fields . magnetohydrodynamic effects seem to be critical for shedding angular momentum in the star formation process and may also act in the early stages of cloud formation . if the magnetic field is so dynamically significant as to produce an instability , it may also provide enough tension to brake the clouds during their formation . @xcite measures the mean field strength in m33 as @xmath263 , which gives an alfvn speed of @xmath2606 km s@xmath12 ( assuming a sech@xmath264 density profile to calculate the midplane volume mass density ) . this value is comparable to the sound speed in the warm neutral medium of most galaxies , suggesting that mhd braking and cloud formation via instabilities occur on comparable timescales . the braking time is set by the time needed for an alfvn wave to sweep through a volume of diffuse gas with a moment of inertia equal to that of the forming cloud @xcite . if the atomic gas has a constant density , then the alfvn wave must pass through a distance comparable to the accumulation length for the molecular cloud . instabilities cause cloud formation on a time scale comparable to the sound crossing time for the accumulation length . since the crossing times for sound and alfvn waves are comparable , we conclude that mhd braking is a viable option to slow the rotation of forming clouds . because only 10% of clouds show angular momentum approaching the expected values from any of the formation mechanisms ( e.g. figure [ spangcomp ] ) , the mhd braking must occur in the atomic gas or during a small fraction of the molecular cloud lifetime . we return to the implications of these observations for cloud formation in [ finis ] . the molecular clouds in this sample suggest a correlation between specific angular momentum and mass . fitting a power - law relationship between @xmath46 and @xmath265 finds @xmath266 , though there is significant scatter in the data ( @xmath267 , figure [ mags ] ) . a similar correlation appears in the milky way data where @xcite finds @xmath268 . if the molecular clouds form by accumulation of atomic gas , then the angular momentum should scale as the accumulation length squared ( equation [ jgal ] ) : @xmath269 . the mass of the cloud is @xmath270 , so a correlation is expected with @xmath271 . the variations in the mean hydrogen surface density are small compared to the order of magnitude spanned in mass ( [ comparison ] ) , so the angular momentum is expected to scale with mass for any accumulation model . that @xmath272 instead of @xmath273 may be due to the action of the braking mechanism , though @xmath273 is not strongly ruled out by the poor quality of the fit . such correlation between @xmath220 and @xmath274 is also expected for a turbulent velocity field . bb00 find that the velocity gradient scales with clouds size @xmath41 as @xmath275 so @xmath276 . the clouds in our sample have a constant surface density regardless of cloud size ( [ comparison ] ) . therefore , the mass of a cloud is proportional to its area @xmath277 and @xmath278 , close to the observed trend . there is no significant variation of specific angular momentum as a function of galactic radius , contrary to the predictions of all the accumulations mechanisms considered here ( figure [ spangcomp ] ) . this implies that the angular momentum of the clouds does not depend on any of the properties that change across the galactic disk , including galactic shear , surface mass density of stars and atomic gas , interstellar pressure , interstellar radiation field , or metallicity . the position angle of the angular momentum vector can be measured from the velocity gradients as discussed in [ velgrad ] . the data show correlations between the cloud position angles and that of the galaxy as well as among the individual gmcs . if the angular momentum is set entirely by the galactic shear , then the rotation axes of the gmcs should be aligned with the galaxy . the distribution of gradient position angles is shown in figure [ pahist ] , including rough divisions between prograde and retrograde rotators ( assuming the gradients represent rotation ) . because of the unknown inclination of the clouds relative to the line of sight , we analyze the distribution of position angles statistically . we assume that the clouds are distributed with orientations on the sphere set by the probability distribution function ( pdf ) : @xmath279^{1/\alpha-1 } \frac{\sin \theta}{2}\label{pdf}\ ] ] where @xmath280 is the angle between the angular momentum vector of the cloud and that of the galaxy , @xmath15 is a parameter that determines the degree of alignment between these vectors , and @xmath281 is the azimuthal angle . for @xmath282 , the orientation angles are randomly distributed on the sphere so there are an equal number of prograde and retrograde rotators . for @xmath283 , the clouds are closely aligned with the galaxy ( @xmath284 implies that 91% of the clouds are prograde rotators ) . this pdf is motivated solely for ease of simulation so that a single parameter @xmath15 determines how well aligned the clouds are with the galaxy . by determining the value of @xmath15 that most closely represents the observed distribution of position angles , we measure the degree of alignment between the clouds and the galaxy . we generated position angle distributions following this pdf using monte carlo simulations and then used a one - sided k - s test to measure the difference between the observed and simulated distributions . after testing a range of @xmath15 , we found the most probable value is @xmath285 ( with k - s likelihood @xmath286 ) , implying 61% of the clouds are prograde rotators . the likelihood of a random distribution on the sphere ( @xmath282 ) is significantly lower ( @xmath287 ) implying some alignment between the clouds and the galaxy . nevertheless , the wide range of position angles indicates any angular momentum imparted by galactic shear is randomized in some fashion . in addition to the cloud - galaxy correlation , nearby clouds show a higher degree of correlation between their gradient position angles . figure [ pacorr ] shows the difference in position angle between pairs of clouds as a function of cloud separation . this figure uses clouds with @xmath288 since these clouds have the most significant gradients . if the clouds are randomly oriented with respect to each other , the value of this statistic should be @xmath213 , but clouds with separations smaller than 500 pc show a significantly smaller value implying their angular momentum vectors are aligned . this alignment would be expected if these neighboring clouds formed from the same parent cloud of . if clouds are the product of large scale motions in the diffuse ism , this 500 pc length may represent the scale of the flows that give rise to the clouds . the clouds in the m33 observations have similar radii ( @xmath289 pc ) , masses ( @xmath290 ) and velocity dispersion fwhms ( 5 @xmath291 10 km s@xmath12 ) as those found in the milky way by s87 . we tested these similarities in more detail and found the gmcs in m33 were indistinguishable from those in the milky way . we emphasize comparison of our results with the work done by s87 because both studies use equivalent methods for determining the properties of the molecular clouds and the sensitivities are comparable : @xmath2600.7 k km s@xmath12 for s87 vs. 0.6 @xmath291 1.3 k km s@xmath12 for this work . we only use the 23 clouds that are well - resolved ( @xmath292 pc ) and round ( @xmath293 ) in these comparisons since the derived properties of these clouds are the most reliable . the results of paper i show that the mass spectrum for gmcs in m33 differs from that found in the milky way : @xmath294 for m33 vs. @xmath295 for the milky way ( s87 ) . despite differences in the mass distribution , clouds in m33 show the same power law relationships between size , mass and linewidth as are seen in the milky way ( larson s laws , after @xcite , see also s87 ) . we plot the size linewidth and the mass linewidth relationship for the clouds in m33 in figure [ larson ] along with the data from the milky way @xcite . where feasible , the cloud properties of the milky way data have been recomputed using the methods in [ cloudprops ] to ensure a common basis for comparison . fitting power - laws to the two relationships shows @xmath296 and @xmath297 . the fits are consistent with the relations seen in the milky way ( s87 ) in both normalization and scaling . however , cloud sizes in m33 are systematically smaller by @xmath298% in m33 compared to s87 , which is most likely due to differences in the size measurement technique . figure [ surfdens ] shows the mean surface mass density within molecular clouds as a function of cloud mass . this figure shows no significant scaling of surface density with mass . similar plots of surface density as a function of cloud radius and galactic radius also show no scaling . the slopes of linear fits between the mass density and cloud mass or cloud radius are consistent with zero . in addition , two statistical tests of correlation , the spearman rank order and the kendall @xmath299 tests show no significant correlation between mass , radius and surface density ( see * ? ? ? * ) . we conclude that gmcs have a surface mass density of @xmath300 ( @xmath301 ) with a dispersion of 60% , which does not vary with cloud mass or radius . this constant mass density is also seen for the gmcs in the milky way @xcite . the consistency of larson s laws between the milky way and m33 shows that the macroscopic properties of a gmc ( @xmath41 , @xmath302 , @xmath303 ) are the same in both galaxies for a given cloud mass . since these macroscopic properties follow similar trends , it is reasonable to expect that the internal properties of gmcs depend only on the mass of the cloud . the gmcs throughout the local group also follow larson s laws ; the lmc @xcite , andromeda @xcite , and dwarf elliptical galaxies @xcite all show some evidence that cloud properties are set by cloud mass . some unifying mechanism must establish the macroscopic properties of the cloud solely in terms of the cloud mass . since turbulence could provide a relationship between size and linewidth , the balance between turbulent support and self - gravity would naturally set the macroscopic properies of a cloud solely in terms of its mass @xcite . in m33 , we are presented with a unique opportunity to study the effects of galactic environment on the co - to - h@xmath5 conversion factor ( @xmath180 ) since there are no systematic differences due to inhomogeneous observation techniques or multiple galaxies . many studies report a variation in the @xmath180 factor as a function of metallicity _ e.g. _ @xcite and references therein . there is no evidence for such a trend in m33 . in figure [ xfac2 ] , we plot the ratio of the luminous to virial mass @xmath200 as a function of metallicity for the 23 well - resolved ( @xmath292 pc ) , round ( @xmath196 ) gmcs in our study . the metallicity at each point is obtained using the position of the cloud and the metallicity gradient ( @xmath304}/dr$ ] ) of @xcite . fitting a line to the data gives : @xmath305-[\mathrm{o / h}]_{\odot}\right)+(0.88 \pm 0.09)\ ] ] accounting for errors in both the metallicity ( 0.1 dex ) and the mass ratio @xcite . the value of @xmath198 for the fit is 0.9 . the value of @xmath198 using the relationship of ( * ? ? ? * dotted line ) as a fit gives 3.31 , showing poor agreement ( @xmath306 ) with their quoted trend . the slope of our fit is consistent with _ no variation in the conversion factor over a range of 0.8 dex in metallicity _ ( a factor of 6 ) . @xcite note that the ratio between virial and co masses does not change systematically with radius in the milky way . in [ mass_sec ] , we argue that interferometer observations overestimate the ratio @xmath200 by _ at most _ a factor of 1.5 . this can not account for the discrepancy with the @xcite data , which we attribute to the difficulties in synthesizing a homogeneous data set from multiple observational studies using a variety of analysis techniques . the studied gmcs range in galactocentric radius from 170 pc to 4000 pc , and there are significant changes in galactic properties over this range . the interstellar radiation field changes value by nearly an order of magnitude over this range in galactic radius @xcite . other variations include changes in the cosmic ray flux and the midplane pressure of the gas . such robustness of the @xmath180 factor as a gmc mass measure is observed in the milky way ( s87 ) , but variations among galaxies may still produce different values in the conversion factor . for example , the @xmath180 factor may change for gmcs in even lower metallicity systems such as the smc that have an average metallicity below the minimum 8.1 observed in m33 . this study of m33 suggests several attributes of the molecular cloud formation process . ( 1 ) molecular clouds form directly from atomic hydrogen rather than the agglomeration of small molecular clouds . ( 2 ) the formation process makes both low mass and high mass molecular clouds in regions of cloud formation . ( 3 ) the formation events are local , _ i.e. _ length scales less than 500 pc . ( 4 ) the progenitor gas has its initial angular momentum dissipated by mhd effects . ( 5 ) the similarity of molecular clouds across many environments implies that the molecular mass distribution sets the properties of molecular clouds and star formation . our results complement those of paper i where it is argued that molecular clouds form directly from atomic hydrogen . in that paper , the striking correspondence between molecular clouds and dense atomic filaments strongly suggests cloud formation from atomic gas . this work strengthens that suggestion since we find no evidence for diffuse molecular gas that could serve as a precursor to gmcs ( [ fluxrec ] ) . additionally , the atomic gas is significantly more massive than the molecular component on a global as well as a local ( @xmath307 pc ) scale . if diffuse _ molecular _ gas were the precursor material , the angular momentum problem would be greatly exacerbated , scaling predicted angular momenta up by a factor of @xmath308 . we also find that the flux not recovered in paper i survey can be accounted for by halos of molecular gas around the detected gmcs , comprised in part by low mass molecular clouds ( [ fluxrec ] ) . these low mass clouds may form in the same event as the high mass cloud at the center of the interferometer field . such low mass molecular clouds would have easily been detectable in the off fields of the 12-m observation and may be restricted to regions where high mass molecular clouds also form . the position angle correlations in [ pacorrs ] suggest that the formation of molecular clouds occurs on length scales less than 500 pc . a common formation event could produce aligned molecular clouds , analogous to the formation of the solar system producing aligned rotation in the planets . correlations in the orientation of angular momentum can be predicted in simulations of turbulent cloud formation that include realistic models of galactic shear . such predictions should show the observed degree of alignment with the galaxy and correlations among the gmcs . the angular momentum problem can be solved by appealing to mhd braking . forming the molecular clouds from a narrow range of radii requires a long formation time . formation mechanisms that accumulate gas supersonically can not have any angular momentum dissipated by alfvn waves since the accumulation time is smaller than crossing times for magnetosonic waves . in contrast , the magnetic field is sufficient to brake forming molecular clouds and braking occurs over timescales comparable to those of instabilities that could potentially form molecular clouds ( [ mhdsec ] ) . molecular clouds appear to have their macroscopic properties ( @xmath231 , @xmath302 ) set by their masses ( [ comparison ] ) . in addition , there appears to be a constant star formation rate per unit molecular mass within galaxies @xcite . if this is true , then the properties of star formation on a galactic scale depend on the amount of atomic gas converted into molecular clouds and little else . although there are similarities in the properties of molecular clouds for a fixed mass , there is good evidence that the mass distribution of molecular gas into individual clouds varies among galaxies . different mass spectra may be the hallmark of multiple formation mechanisms converting atomic into molecular gas . the steep mass spectrum for the molecular clouds in m33 ( paper i ) represents the _ only _ difference in the molecular cloud population between m33 and the milky way . the mass distribution of molecular gas is thus the dominant factor controlling star formation on a local and galactic scale .

we place upper limits on the specific angular momentum of the gmcs and find the observed values to be nearly an order of magnitude below the values predicted from simple formation mechanisms . these observations suggest that molecular clouds form locally out of atomic gas with significant braking by magnetic fields to dissipate the angular momentum imparted by galactic shear . the observed gmcs share basic properties with those found in the galaxy such as similar masses , sizes , and linewidths as well as a constant surface density of 120 pc .

we presentco observations of 45 giant molecular clouds in m33 made with the bima array . the observations have a linear resolution of 20 pc , sufficient to measure the sizes of most gmcs in the sample . we place upper limits on the specific angular momentum of the gmcs and find the observed values to be nearly an order of magnitude below the values predicted from simple formation mechanisms . the velocity gradients across neighboring , high - mass gmcs appear preferentially aligned on scales less than 500 pc . if the clouds are rotating , 40% are counter - rotating with respect to the galaxy . gmcs require a braking mechanism if they form from the large scale radial accumulation of gas . these observations suggest that molecular clouds form locally out of atomic gas with significant braking by magnetic fields to dissipate the angular momentum imparted by galactic shear . the observed gmcs share basic properties with those found in the galaxy such as similar masses , sizes , and linewidths as well as a constant surface density of 120 pc . the size linewidth relationship follows , consistent with that found in the galaxy . the cloud virial masses imply that the co - to - h conversion factor has a value of and does not change significantly over the disk of m33 despite a change of 0.8 dex in the metallicity .

1012.3561

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in the preceding section we have described the important features of the boundary energy density @xmath159 induced by a relativistic coiling string in the bulk . we proposed approximating this by a superposition of gravitational shock waves produced by each string bit we dubbed this the ` beaming mechanism ' and calculated the consequences of this proposal . in particular , we have obtained the characteristic spiral pattern of synchrotron radiation ( cf . e.g. ) . we have calculated the spacing , phase , width , speed of propagation , and polar extent , of each energy pulse , and found each of these characteristic features in complete quantitative agreement with the computations of @xcite . our results suggest that it is indeed valid to view the string s backreaction as given by superposition of gravitational shock waves . from a computational perspective , this presents a major simplification : instead of having to solve the full linearized einstein s equations in the bulk , we merely need to find geodesics . in fact , this provides a useful tool for understanding the radiation of a relativistic quark following an arbitrary trajectory , since the string tends to become more relativistic deeper in the bulk and develops a worldsheet horizon , making the approximation more accurate further away from the quark . since for any quark trajectory the corresponding string motion is known explicitly @xcite , we can construct the just as easily as for the synchrotron case discussed above . encouraged by the success in using in ads to reproduce the synchrotron radiation in strongly coupled medium at zero temperature calculated in @xcite , a natural question to ask is whether this method also applies in the case of non - zero temperature . indeed , once one generalizes the gsw construction to schwarzschild - ads background , one should likewise be able to estimate at least some part of the quark s radiation in a thermal strongly - coupled plasma , which should suffice to reproduce , for instance , the diffusion wake and sonic boom generated by a moving quark @xcite . however , it is important to realize that in the presence of a bulk ads black hole , the string no longer remains relativistic deep in the bulk , so the approximation will have much more constrained regime of validity in particular , it will no longer improve with distance from the quark . zeroth order expectations from directly adapting our geodesic construction would suggest that the radiation which starts out collimated diffuses on a thermal scale ; as is indeed consistent with expectations form the field theory side . moreover , the construction of a gravitational shock wave itself , in schwarzschild - ads background , is substantially more involved and is it no longer guaranteed that the metric perturbation from schwarzschild - ads due to a relativistic particle would remain similarly localized . nevertheless , given some region where the approximation is accurate , it may be possible to go beyond the initial regime of validity by performing series expansion in @xmath160 and building up the backreaction effects order - by - order . we however leave this for future work . finally , we end with the issue which originally motivated the present work , namely how the observed beaming effect bears on the scale / radius duality . recall that scale / radius ( or uv / ir ) duality @xcite , which has been one of the first and most important entries in the ads / cft dictionary , suggests that the closer a bulk excitation is to the ads boundary , the smaller is the characteristic size of the dual cft excitation . this provides an important insight into the holographic nature of the ads / cft duality : the ` extra ' ( radial ) dimension in the bulk arises from a scale in the dual cft . this intuition has bolstered our understanding of various dynamical processes . for example , the field theory notion of color transparency , that different - scale excitations pass through each other without interacting , is beautifully explained by bulk locality : in the bulk , the corresponding excitations do not interact due to being separated in the radial direction . from this , one might have naively expected that same - scale excitations passing through each other would interact . however , the present context emphasized that naive applications of the scale / radius duality should be treated with caution . in particular , as we have seen , a source deep in the bulk of ads may nevertheless produce a sharply - localized effect on the boundary . by taking an ordinary source and a beamed source , we can engineer a situation where two excitations with ( instantaneously ) similar characteristic scale do not interact ( because within the bulk they are well separated ) , as well the converse situation where two excitations with widely differing scale nevertheless do interact ( because the dual bulk excitations collide with each other ) . the beaming mechanism , which underlies such constructions , is quite interesting . the relativistic velocity of the string causes the backreaction due to each string bit to be localized on a co - dimension one surface of the gsw . although the size of this surface grows with the bulk position of the source ( it has larger radius for the string bits deeper in bulk ) , the dominant effect is sharply peaked . the final ingredient , however , is the superposition of all the gsws from individual string bits , as emphasized most clearly by . it is due to this combined effect that the radiation pulse on the boundary does not broaden as it propagates outward . it is a pleasure to thank paul chesler , roberto emparan , gary gibbons , gary horowitz , hong liu , shiraz minwalla , rob myers , joe polchinski , and mukund rangamani for valuable discussions . i would also like to thank mit , ubc , galileo galilei institute , and imperial college london for their hospitality during this project . this work is supported in part by a stfc rolling grant .

in particular , we offer a heuristic explanation of the collimated nature of synchrotron radiation produced by a circling quark , which was recently studied in phys.rev.*d81 * ( 2010 ) 126001 . dcpt-10/75 * holographic dual of collimated radiation * veronika e. hubeny + _ science laboratories , south road , durham dh1 3le , united kingdom _ +

we propose a new and simple method of estimating the radiation due to an accelerated quark in a strongly coupled medium , within the framework of the ads / cft correspondence . in particular , we offer a heuristic explanation of the collimated nature of synchrotron radiation produced by a circling quark , which was recently studied in phys.rev.*d81 * ( 2010 ) 126001 . the gravitational dual of such quark is a coiling string in ads , whose backreaction on the spacetime geometry remains tightly confined , as if ` beamed ' towards the boundary . while this appears to contradict conventional expectations from the scale / radius duality , we resolve the issue by observing that the backreaction of a relativistic string is reproduced by a superposition of gravitational shock waves . we further demonstrate that this proposal allows us to reduce the problem of computing the boundary stress tensor to merely calculating geodesics in ads , as opposed to solving linearized einstein s equations . dcpt-10/75 * holographic dual of collimated radiation * veronika e. hubeny + _ science laboratories , south road , durham dh1 3le , united kingdom _ +

1111.4599

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the term hydraulic jump " refers to the sudden jump in fluid height , as for example observed in the outward spreading water layer in a kitchen sink , resulting from the impact of the water from the tap with the horizontal bottom of the sink @xcite . similar phenomena are seen in rivers with large tidal variation at the outlet and are known as river bores " . river bores move up the rivers , whereas hydraulic jumps are stationary , either due to spatial inhomogeneities or to the geometric configuration of the flow . in the kitchen sink , the jump occurs on a more or less circular locus . close to the point of impact the water level is very thin , but at a certain radius , @xmath1 , the level increases abruptly forming a circular jump . the water flow and thus the jump shape in a kitchen sink fluctuate , but by building a more symmetric experimental setup and/or using a more viscous fluid , one may obtain a completely stationary and axisymmetric flow , where the jump occurs on a surprisingly well - defined circle ( fig . [ fig : circularjump ] ) . it has been shown @xcite that circular hydraulic jumps can undergo a sequence of structural changes seen by varying the fluid height @xmath2 downstream of the jump . this can be achieved by inserting an adjustable circular weir at the rim of the circular impact plate . when increasing @xmath2 , the jump becomes steeper until , at a critical value of @xmath2 , the jump becomes unstable and loses its balance . like a breaking wave , it creates a new stationary state with a wider jump region and a new flow structure in which the surface flow is reversed due to a separation vortex ( referred to in the following as the `` roller '' ) . following @xcite , his new flow structure is called a _ type ii jump _ to distinguish it from the `` ordinary '' _ type i jump_. the most remarkable observation about the type ii state is that the jump typically loses its azimuthal symmetry and attains the shape of a regular , though not necessarily straight - edged , polygon ( fig . [ fig : polyjump ] ) . in this paper , we present a phenomenological model for the type ii jump , which we believe to include the basic mechanisms of the flow rendering the circular state unstable and giving the polygonal jump its peculiar shape . this allows us to obtain the qualitative dependence of the jump shape on the control parameters available , primarily the outer fluid height @xmath2 , and the properties of the fluid , i.e. , viscosity and surface tension . for experimental data , we refer to earlier work . our own experiments are performed with the same setup as in @xcite and is only used qualitatively as a visual guide ( see also supplementary movies @xcite ) . for the type i state , averaging theory with a variable profile gives at least qualitatively the right flow structure including the separation region on the bottom , outside the jump @xcite . for the type ii state with separation at the surface , no such theory exists , and we therefore from the outset assume a flow structure derived from experiments . our model extends earlier models proposed in @xcite , based on the competition between gravitational and viscous effects . in @xcite a radial force balance for the roller was used together with a line tension " to derive polygonal shapes . in @xcite it was shown that such a line tension is not necessary and that a more satisfactory model is obtained by taking into account the azimuthal flow . this is the approach used in the present paper . it was recently pointed out @xcite , however , that the instability forming the polygonal jumps seems to be driven , at least in part , by surface tension ( see also supplementary materials @xcite ) . thus , surface tension is included in our model and indeed the instability forming the polygonal jumps seems to be closely related to the rayleigh - plateau instability for the liquid cylinder " formed by the roller . in this paper , we treat both linear and nonlinear properties of our model . for the linear properties , we can with some confidence include the effects of surface tension , but for the fully developed polygonal states , this is very difficult because of the lack of precise data on the height profiles . even without surface tension , our model does have polygonal states , and we compute their shapes assuming that they will be only slightly changed by surface tension effects . the layout of the paper is as follows : we first derive the model and point out the similarities and differences to earlier models . we then solve a nonlinear model with zero surface tension analytically and show that it has many features that are expected from experiments . finally , we compute the temporal stability of the circular state while including surface tension , and show that it has properties close to the rayleigh - plateau instability .

we propose a phenomenological model for the polygonal hydraulic jumps discovered by ellegaard _ et al . _ , based on the known flow structure for the type ii hydraulic jumps with a `` roller '' ( separation eddy ) near the free surface in the jump region . a truncated , but fully nonlinear version of the model can be solved analytically . finally , we include time - dependent terms in the model and study linear stability of the circular state .

we propose a phenomenological model for the polygonal hydraulic jumps discovered by ellegaard _ et al . _ , based on the known flow structure for the type ii hydraulic jumps with a `` roller '' ( separation eddy ) near the free surface in the jump region . the model consists of mass conservation and radial force balance between hydrostatic pressure and viscous stresses on the roller surface . in addition , we consider the azimuthal force balance , primarily between pressure and viscosity , but also including non - hydrostatic pressure contributions from surface tension in light of recent observations by bush _ et al_. the model can be analyzed by linearization around the circular state , resulting in a parameter relationship for nearly circular polygonal states . a truncated , but fully nonlinear version of the model can be solved analytically . this simpler model gives rise to polygonal shapes that are very similar to those observed in experiments , even though surface tension is neglected , and the condition for the existence of a polygon with n corners depends only on a single dimensionless number . finally , we include time - dependent terms in the model and study linear stability of the circular state . instability occurs for sufficiently small bond number and the most unstable wave length is expected to be roughly proportional to the width of the roller as in the rayleigh - plateau instability . _ _

hep-ph0011306

c

we have worked out a simple and accurate prescription to calculate the solar neutrino survival probability @xmath0 in the quasivacuum oscillation regime . such prescription adapts the known analytical solution for the exponential case to the true density case , as well as to the perturbative solution of neutrino evolution equations in the limit of small @xmath25 . the accuracy of the prescription is significantly improved ( up to @xmath244 in @xmath0 in the whole qvo range ) by replacing the familiar prescription of choosing the scale height parameter @xmath2 at the msw resonance point by a new one : @xmath2 is chosen at the point of maximal violation of adiabaticity ( mva ) along the neutrino trajectory in the sun . such generalization preserves a smooth transition of our prescription from the qvo to the msw oscillation regime , where the two prescriptions practically coincide . we show that at sufficiently small @xmath245 in the qvo regime , the effective value of @xmath2 is determined by an integral over the electron density distribution in the sun , @xmath18 : @xmath246 where @xmath118 . the main contribution in the above integral is shown to come from the region corresponding to the convective zone of the sun , @xmath247 . thus , if quasivacuum oscillations take place , solar neutrino experiments might provide information about the density distribution in the convective zone of the sun . we also discuss in detail the phase acquired by neutrinos in the sun , whose observability , although possible in principle , poses a formidable challenge for future experiments aiming to observe short timescale variations of fluxes from solar @xmath3 lines . a.m. acknowledges kind hospitality at sissa during the initial stage of this work . s.t.p . would like to acknowledge the hospitality of the aspen center for physics where part of this work was done . the work of e.l . , a.m. , and a.p.was supported in part by the italian murst under the program `` fisica astroparticellare . '' the work of s.t.p . was supported in part by the eec grant erbfmrxct960090 and by the italian murst under the program `` fisica teorica delle interazioni fondamentali . ''

we propose a simple prescription to calculate the solar neutrino survival probability in the quasivacuum oscillation ( qvo ) regime . the resulting analytical recipe for the calculation of is shown to reach its highest accuracy ( in the whole qvo range ) when the familiar prescription of choosing the solar density scale parameter at the mikheyev - smirnov - wolfenstein ( msw ) resonance point is replaced by a new one , namely , when is chosen at the point of `` maximal violation of adiabaticity '' ( mva ) along the neutrino trajectory in the sun . the mva prescription admits a smooth transition from the qvo regime to the msw transition one . we discuss in detail the phase acquired by neutrinos in the sun , and show that it might be of relevance for the studies of relatively short timescale variations of the fluxes of the solar lines in the future real - time solar neutrino experiments .

we propose a simple prescription to calculate the solar neutrino survival probability in the quasivacuum oscillation ( qvo ) regime . such prescription is obtained by matching perturbative and exact analytical results , which effectively take into account the density distribution in the sun as provided by the standard solar model . the resulting analytical recipe for the calculation of is shown to reach its highest accuracy ( in the whole qvo range ) when the familiar prescription of choosing the solar density scale parameter at the mikheyev - smirnov - wolfenstein ( msw ) resonance point is replaced by a new one , namely , when is chosen at the point of `` maximal violation of adiabaticity '' ( mva ) along the neutrino trajectory in the sun . the mva prescription admits a smooth transition from the qvo regime to the msw transition one . we discuss in detail the phase acquired by neutrinos in the sun , and show that it might be of relevance for the studies of relatively short timescale variations of the fluxes of the solar lines in the future real - time solar neutrino experiments . finally , we elucidate the role of matter effects in the convective zone of the sun .

1512.05054

i

multifractional brownian motion ( mbm ) is considered as one of the most natural extensions of fractional brownian motion ( fbm ) . nowadays applications of mbm are numerous and growing . similar to fbm , mbm has been used in such diverse areas as geology , image analysis , signal processing , traffic networks and mathematical finance . for instance , we refer to lvy - vhel ( 1995 ) , bertrand et al . ( 2012 ) and bianchi et al . ( 2013 ) . in this brief introduction , we focus on applications to mathematical finance , which we know best . since generally neither fbm nor mbm are semi - martingales , rogers ( 1997 ) pointed out that there would be arbitrage in a market where stocks are modelled by fbm . however , cheridito ( 2003 ) showed that , if one relaxes the definition of arbitrage , fbm is an excellent candidate to model long - term memory in stock markets . bayraktar et al . ( 2006 ) obtained fbm as the limit of the stock price in an agent - based model where investors display inertia . moreover , unlike stock prices , several processes , like stochastic volatility , exchange rates , or short interest rates do not need to be semi - martingales for a mathematical model to be arbitrage - free in a strict sense . for each of these processes , there is empirical evidence of long - term memory . we refer to corlay et al . ( 2014 ) for stochastic volatility , xiao et al . ( 2010 ) for exchange rates , and ohashi ( 2009 ) for interest rates . making the hurst parameter time - dependent allows to model different regimes of the stochastic process of interest . for example , in times of financial crisis , asset volatility rises significantly . likewise , empirical evidence shows that there has been periods of different volatility in either exchange rates or interest rates . this phenomena motivates one to introduce mbm into finance , since unlike fbm , the local regularity of volatilities driven by mbm allows to change via different periods . let @xmath0 denote an mbm with hurst function @xmath1 . we consider a general model @xmath2 with @xmath3 , @xmath4)$ ] . in this paper we are interested in estimating @xmath1 , starting from the observations of @xmath5 . an advantage of our model and methodology is that the functions @xmath6 and @xmath7 do not need to be known a priori . this is for instance the case of stochastic volatility , where the volatility @xmath8 is an unknown @xmath9 class function of @xmath10 . we define the mbm @xmath11}$ ] through its harmonizable representation ( see benassi et al . 1997 ) : for @xmath12 $ ] , @xmath13 where : @xmath14 : : the hurst functional parameter @xmath15 is a @xmath16-hlderian function with some @xmath17 ; @xmath14 : : the complex - valued stochastic measure @xmath18 is defined as the fourier transform of the real - valued brownian measure @xmath19 . more precisely , for all @xmath20 , @xmath21 where @xmath22 denotes the fourier transform of @xmath23 : @xmath24 statistically , the most significant feature of mbm , its local hlder regularity , can be measured by its pointwise hlder exponent . recall that for a continuous nowhere differentiable process @xmath25 , its pointwise hlder exponent @xmath26 is a stochastic process defined by : for each @xmath27 , @xmath28:~\limsup\limits_{\epsilon\rightarrow0}\frac{|y(t_0+\epsilon)-y(t_0)|}{|\epsilon|^{\alpha}}=0\big\}.\ ] ] ayache and lvy - vhel ( 2004 ) show that for each @xmath29 , the pointwise hlder exponent of @xmath30 at each point @xmath27 , @xmath31 , is with probability @xmath32 equal to its hurst functional parameter @xmath33 : @xmath34 since generating the scenarios of fbm and mbm relies only on their hurst parameters ( see ayache and lvy - vhel 2004 ) , the problem of estimation of the hurst parameter has significant interests . several results have already been obtained recently on the estimation of the mbm s hurst functional parameter . we refer to rosenbaum ( 2008 ) , coeurjolly ( 2005 , 2006 ) , bardet ( 2002 ) , bardet and surgailis ( 2013 ) and bertrand et al . ( 2013 ) . rosenbaum ( 2008 ) and bardet ( 2002 ) used wavelet - based methods to study inference problem on fbm , i.e. , the hurst parameter is constant ; coeurjolly ( 2005 , 2006 ) and bertrand et al . ( 2013 ) studied the estimation of @xmath35 by using respectively generalized variations ( see also chan et al . 1995 ) and increment ratio statistic method , where a discretized sample path of the mbm is assumed to be observed . bardet and surgailis ( 2013 ) developed a nonparametric estimation method ( based on the increment ratio ) for evaluating the local hurst function of a multifractional gaussian process ( whose increments are asymptotically a multiple of an fbm ) which extends mbm , starting from a discrete sample path of this process . in this work we consider a model more general than mbm but slightly less general than the one considered in bardet and surgailis ( 2013 ) . we study a different statistical setting ( either the wavelet coefficients of @xmath5 or a discrete path of @xmath36 points is observed ) , by applying a wavelet - based approach . note that the main advantage of this statistical setting is that , it could be applied to inferential problems when only a set of wavelet coefficients are available ( we refer to delbeke and van ( 1995 ) , abry et al . ( 2002 ) , abry and conalvs ( 1997 ) and the references therein ) . by a study on the fine regularity property , our central limit theorem provides an explicit form for the limit covariance matrix . it is worth noting that , the construction of our estimator relies on a sharp estimation of the covariance structure of the mbm s wavelet coefficients . the main technical difficulty arises due to the fact that the covariance structure of mbm is much more complicated than that of fbm . the techniques used to identify such covariance structure is not obvious and thus has its specific interests in statistical inferences on multifractional processes as well as on stochastic analysis . consider the following system : for @xmath12 $ ] , @xmath37 where @xmath14 : : @xmath38 is an mbm defined in ( [ mbm ] ) . assume that its hurst functional parameter @xmath1 belongs to @xmath39)$ ] and @xmath40}h(t),\sup\limits_{t\in[0,1]}h(t)\big]\subset(0,1);\ ] ] @xmath14 : : the closed forms of the deterministic functions @xmath6 and @xmath7 are unknown . however we assume that + @xmath41 ; ; @xmath3 , @xmath42 almost everywhere and there exist two constants @xmath43 such that @xmath44 for all @xmath45 . @xmath46 ; ; @xmath47)$ ] and @xmath48 almost everywhere . @xmath14 : : suppose that a discrete trajectory of @xmath5 : @xmath49 is observed for some @xmath50 large enough . our major goal is to evaluate the functional parameter @xmath15 . as in coeurjolly ( 2005 , 2006 ) , we introduce a pointwise estimation method , namely , the function @xmath15 is estimated pointwisely for any @xmath29 . once the time @xmath27 is fixed , the problem becomes a parametric estimation problem . peng ( 2011a ) studied this problem when @xmath8 is some stationary increment process ( with @xmath51 ) , where the optimal convergence rate @xmath52 is obtained by using the observations @xmath53 . however , when @xmath1 varies via time , the estimation of @xmath33 only relies on the sample size of the observed data in the neighborhood of @xmath54 and this neighborhood s radius convergence speed . hence the convergence speed of the corresponding estimator would be reasonably slower than @xmath52 ( see e.g. coeurjolly ( 2005 , 2006 ) for a particular case when @xmath5 is mbm ) . in this work , heuristically speaking , since the sample size of the neighborhood data of @xmath54 for estimating each @xmath33 is about @xmath55 , it is then believed that a good estimator should have its convergence rate near @xmath56 . subject to this statistical setting , we try to get the `` optimal '' rate of convergence estimator of @xmath33 by using wavelet basis . let the integer @xmath57 and let us pick any mother wavelet @xmath58)$ ] whose first @xmath59 moments are vanishing : @xmath60 and @xmath61 @xmath62 is called the cancellation order of @xmath63 . fix an integer @xmath64 , with @xmath65 being a subsequence of @xmath66 . the wavelet coefficients of @xmath8 are given by : for @xmath67 , @xmath68 we introduce a set of indices corresponding to a neighborhood of each @xmath29 : @xmath69 where the radius of this neighborhood @xmath70 satisfies @xmath71 and @xmath72 as @xmath73 . then the quadratic form estimator of @xmath74 is given as : @xmath75 for showing the consistency of our estimator and existence of central limit results , we need to impose the following technical assumptions to @xmath76 , @xmath62 and @xmath15 : * ( a0 ) : * : : @xmath77 . this condition leads to @xmath78}h(t)>1 $ ] . we remark that the latter inequality still holds when @xmath79 and @xmath80}h(t)<3/4 $ ] , as a consequence our results are still valid . however , we wo nt consider the latter assumptions , because practitioners in data analysis would nt expect the unknown functional parameter @xmath15 should be valued less than @xmath81 . * ( a1 ) : * : : a lower bound of the convergence rate of @xmath70 toward 0 is given as : @xmath82 * ( a2 ) : * : : an upper bound of the convergence rate of @xmath70 toward 0 is described as : for any @xmath83 arbitrarily small , @xmath84 * ( a3 ) : * : : there exists a constant @xmath85 such that @xmath86 . * ( a4 ) : * : : this condition is stronger than * ( a1 ) * : @xmath87 through this paper we assume that * ( a0 ) * is always satisfied . we will successively show that our estimator of @xmath33 is weakly consistent under assumption * ( a1 ) * ; it is strongly consistent under assumptions * ( a1)-(a2 ) * ; and it has an asymptotic gaussian behavior subject to assumptions * ( a2)-(a4)*. before stating these main results , we make some notation conventions : ( a ) : : a sequence @xmath88 of real - valued random variables is said to be bounded almost surely if and only if @xmath89 it is said to be bounded in probability if and only if @xmath90 let @xmath91 be a sequence of strictly positive real numbers and let @xmath88 be a sequence of positive random variables . the notations @xmath92 mean respectively that the sequence @xmath93 is bounded almost surely and in probability . ( b ) : : we say two sequences of strict positive values @xmath91 and @xmath94 are equivalent as @xmath95 tends to infinity if and only if there exist two constants @xmath96 such that @xmath97 we denote the relation of equivalence by @xmath98 . ( c ) : : we use the notations `` @xmath99{a.s.}$ ] '' , `` @xmath99{\mathbb p}$ ] '' and `` @xmath99{dist}$ ] '' to respectively denote convergence @xmath100-almost surely , convergence in probability and convergence in law . it is also useful to briefly introduce the steps which lead to the construction of the estimators : * step 1 : * : : identification of @xmath101 starting from the observations @xmath49 . in order to estimate @xmath101 , it suffices to make an identification of @xmath102 given in ( [ d ] ) . such an identification can be naturally obtained by discretization of integrals to the sum as @xmath103 by lvy s modulus of continuity theorem for mbm ( see e.g. theorem 1.7 in benassi et al . 1997 ) , @xmath4)$ ] , ( [ supx ] ) and the fact that @xmath104}h(u)}=\mathcal o\big(|s - t|^{\max\{h(s),h(t)\}}\big)~\mbox{as}~|s - t|\rightarrow0,\ ] ] there exists a positive - valued random variable @xmath105 all of whose moments are finite , such that for all @xmath106 $ ] with @xmath107 , @xmath108 then , the following important relations hold ( the proofs are given in the appendix ) : @xmath109 which show that @xmath110 is a good estimator of @xmath102 . next we set @xmath111 and show that @xmath112 satisfies @xmath113 please see the appendix for the proof of ( [ widev ] ) . * step 2 : * : : identification of @xmath33 starting from @xmath114 . we use similar computations appeared in peng ( 2011a ) . the main result is the following ( see proposition [ varvx ] for a more explicit formula ) : @xmath115 where @xmath116 is a constant which does not depend on @xmath117 ; @xmath118 denotes the cardinal of @xmath119 . it is observed that @xmath120 therefore subject to feasible choices of the sequence @xmath121 , the following convergence can accordingly take place in probability or almost surely : @xmath122 where @xmath116 is some constant not depending on @xmath117 . * step 3 : * : : identification of @xmath33 starting from @xmath123 . + under assumption * ( a1 ) * ( resp . * ( a1)-(a2 ) * ) , one has the following relation of equivalence ( see ( [ as1 ] ) , ( [ taylor2 ] ) , ( [ diffv_p ] ) and ( [ diffv_as ] ) ) : for @xmath124 , @xmath125 in probability ( resp . almost surely ) . as a consequence , @xmath126 is a consistent estimator of @xmath33 . we remark that the speed of convergence relies on the choice of @xmath127 . more details on the choice of @xmath127 will be discussed in theorem [ vydn ] .

we propose a wavelet - based approach to construct consistent estimators of the pointwise hlder exponent of a multifractional brownian motion , in the case where this underlying process is not directly observed . the relative merits of our estimator are discussed , and we introduce an application to the problem of estimating the functional parameter of a nonlinear model . + * * keywords : * * pointwise hlder exponent ; multifractional process ; wavelet coefficients ; parametric estimation

we propose a wavelet - based approach to construct consistent estimators of the pointwise hlder exponent of a multifractional brownian motion , in the case where this underlying process is not directly observed . the relative merits of our estimator are discussed , and we introduce an application to the problem of estimating the functional parameter of a nonlinear model . + * * keywords : * * pointwise hlder exponent ; multifractional process ; wavelet coefficients ; parametric estimation