bluuebunny/crossref_metadata_2025 huggingface dataset:
Gravitational potential and X-ray luminosities of early-type galaxies observed with XMM-Newton and Chandra
Authors: Nagino Ryo , Matsushita Kyoko
Published: October 2010

We study the dark matter content in early-type galaxies and investigate whether X-ray luminosities of early-type galaxies are determined by the surrounding gravitational potential. We derived gravitational mass profiles of 22 early-type galaxies observed with XMM-Newton and Chandra. Sixteen galaxies show constant or decreasing radial temperature profiles, and their X-ray luminosities are consistent with kinematical energy input from stellar mass loss. The temperature profiles of the other 6 galaxies increase with radius, and their X-ray luminosities are significantly higher. The integrated mass-to-light ratio of each galaxy is constant at that of stars within 0.5–1re, and increases with radius. The scatter of the central mass-to-light ratio of galaxies was less in K-band light. At 3re, the integrated mass-to-light ratios of galaxies with flat or decreasing temperature profiles are twice the value at 0.5re, where the stellar mass dominates, and at 6re, these increase to three times the value at 0.5re. This feature should reflect common dark and stellar mass distributions in early-type galaxies: Within 3re, the mass of dark matter is similar to the stellar mass, while within 6re, the former is larger than the latter by two-fold. In contrast, X-ray luminous galaxies have higher gravitational mass in the outer regions than X-ray faint galaxies. We describe these X-ray luminous galaxies as the central objects of large potential structures; the presence or absence of this potential is the main source of the large scatter in the X-ray luminosity.
JD3 – Neutron Stars: Timing in Extreme Environments
Authors: Belloni Tomaso M. , Méndez Mariano , Zhang Chengmin
Published: October 2010

The space-time around Neutron Stars is indeed an extreme environment. Whether they are in accreting binary systems, isolated or in non-accreting binaries (perhaps with another Neutron Star), Neutron Stars provide a window onto physical processes not accessible by other means. In particular, the study of their time variability: pulsations, quasi-periodic oscillations, thermonuclear X-ray bursts, flares and giant-flares, pulsar glitches and pulse period variations, constitutes a valuable instrument to unveil those very same physical processes. Here we briefly summarize the most important results presented at Joint Discussion 3 of the XXVII IAU General Assembly.
High-frequency quasi-periodic oscillations in accreting neutron-star systems
Authors: Méndez Mariano
Published: October 2010

Kilohertz quasi-periodic oscillations (kHz QPOs) are the fastest (almost coherent) variability measured in accreting X-ray binaries with a neutron-star primary. Here I review the rôle of the neutron-star spin in driving the frequencies of the kHz QPOs.
Accreting millisecond X-ray pulsars: recent developments
Authors: Wijnands Rudy
Published: October 2010

It is now more than eleven years since the discovery of the first accreting millisecond X-ray pulsar. Since then, eleven additional systems have been found, two of them during the last year. Here I briefly discuss the most recent developments with respect to these systems.
JD4 – Progress in Understanding the Physics of Ap and Related Stars
Authors: Cunha Margarida S.
Published: October 2010

Chemically peculiar (CP) stars exhibit, simultaneously, a wide variety of physical phenomena, including diffusion, convection, magnetism, and pulsation. Thus, progress in the understanding of these objects requires the input of researchers from a variety of research fields within stellar astrophysics. The General Assembly of the IAU, in Rio de Janeiro, provided an excellent opportunity to discuss challenging new results faced in CP star research and improve the exchange of information and cooperation with experts of neighbouring scientific fields.
A 3-D look into the atmosphere?
Authors: Wade G. A. , Mashonkina L. , Ryabchikova T. , Krticka J. , Silvester J. , Kochukhov O. , Sousa J. C. , Nomura T. , Wahlgren G. M. , Gruberbauer M. , Hubrig S. , Briquet M. , Yüce K. , Drake N. , Nunez N. , Gray R. O. , Ziznovsky J. , Cowley C. , Shavrina A. , Dworetsky M. , Pintado O. , Polosukhina N. , Cidale L.
Published: October 2010

The atmospheres of chemically peculiar stars can be highly structured in both the horizontal and vertical dimensions. While most prevalent in the magnetic stars, these structures can also exist in non-magnetic stars. In addition to providing an important window to understanding the physical processes at play in these complex atmospheres, they can also be exploited to study stellar pulsations. This article reviews contributions to the session “A 3D look into the atmosphere” of the Joint Discussion “Progress in understanding the physics of Ap and related stars”. It is divided into 3 sections: “Magnetic field and surface structures”, “Pulsations in the atmospheres of roAp stars/inversions”, and “Spectral synthesis/atmospheric models”.
CP and related phenomena in the context of Stellar Evolution
Authors: Braithwaite J. , Akgün T. , Alecian E. , Kholtygin A. F. , Landstreet J. D. , Mathis S. , Michaud G. , Portnoy J. , Alecian G. , Bychkov V. D. , Bychkova L. V. , Drake N. , Fabrika S. N. , Reisenegger A. , Steinitz R. , Vick M.
Published: October 2010

We review the interaction in intermediate and high mass stars between their evolution and magnetic and chemical properties. We describe the theory of Ap-star ‘fossil’ fields, before touching on the expected secular diffusive processes which give rise to evolution of the field. We then present recent results from a spectropolarimetric survey of Herbig Ae/Be stars, showing that magnetic fields of the kind seen on the main-sequence already exist during the pre-main sequence phase, in agreement with fossil field theory, and that the origin of the slow rotation of Ap/Bp stars also lies early in the pre-main sequence evolution; we also present results confirming a lack of stars with fields below a few hundred gauss. We then seek which macroscopic motions compete with atomic diffusion in determining the surface abundances of AmFm stars. While turbulent transport and mass loss, in competition with atomic diffusion, are both able to explain observed surface abundances, the interior abundance distribution is different enough to potentially lead to a test using asterosismology. Finally we review progress on the turbulence-driving and mixing processes in stellar radiative zones.
Joint Discussion 5 Modelling the Milky Way in the Era of Gaia
Authors: Binney James J.
Published: October 2010

The body of photometric and astrometric data on stars in the Galaxy has been growing very fast in recent years (Hipparcos/Tycho, OGLE-3, 2-Mass, DENIS, UCAC2, SDSS, RAVE, Pan Starrs, Hermes, . . .) and in two years ESA will launch the Gaia satellite, which will measure astrometric data of unprecedented precision for a billion stars. On account of our position within the Galaxy and the complex observational biases that are built into most catalogues, dynamical models of the Galaxy are a prerequisite full exploitation of these catalogues. On account of the enormous detail in which we can observe the Galaxy, models of great sophistication are required. Moreover, in addition to models we require algorithms for observing them with the same errors and biases as occur in real observational programs, and statistical algorithms for determining the extent to which a model is compatible with a given body of data.

JD5 reviewed the status of our knowledge of the Galaxy, the different ways in which we could model the Galaxy, and what will be required to extract our science goals from the data that will be on hand when the Gaia Catalogue becomes available.
Structure and evolution of the Milky Way: the interstellar medium perspective
Authors: Boulanger François
Published: October 2010

The Herschel and Planck satellites have started imaging the sky at far-IR to mm wavelengths with an unprecedented combination of sky and spectral coverage, angular resolution, and sensitivity, thus opening the last window of the electromagnetic spectrum on the Galaxy. Dedicated observing programs on Herschel and the Planck all-sky survey will provide the first complete view at cold dust across the Galaxy, opening new perspectives on the structure and dynamical evolution of the Milky Way relevant to Gaia. The analysis and modelling of these observations will contribute to our understanding of two key questions: how do stars form from interstellar matter? how are the interstellar medium and the magnetic field dynamically coupled? The comparison with Gaia observations will contribute to build a 3D model of the Galactic extinction taking into account dust evolution between ISM components
Schwarzschild Models for the Galaxy
Authors: Chanamé Julio
Published: October 2010

Schwarzschild's orbit-superposition technique is the most developed and well-tested method available for constraining the detailed mass distributions of equilibrium stellar systems. Here I provide a very short overview of the method and its existing implementations, and briefly discuss their viability as a tool for modeling the Galaxy using Gaia data.
How to build a 3D extinction model of the Galaxy
Authors: Lépine J. R. D. , Amôres E. B.
Published: October 2010

We show that anomalous extinction (deviations from the traditionally adopted RV = AV/E(B − V) = 3.1 introduces large uncertainties in the distances of stars, for distances larger than 1-2 kpc. We argue that for such distances and for directions close to the galactic plane, the use of extinction models based on the gas distribution in the Galaxy is safer, for the moment, than the use of extinction maps.
JD6 -Time and Astronomy Preface and Posters
Authors: Defraigne Pascale
Published: October 2010

Responsibility for the definition of time scales left the astronomical community some 40 years ago when, in 1967, the second became defined by an atomic transition in the International System of units SI and when International Atomic Time (TAI) was defined as the primary international time scale in 1971.
New solution of Earth Orientation Parameters in 20th century
Authors: Vondrák Jan , Ron Cyril , Štefka Vojtěch
Published: October 2010

We present a new solution of Earth Orientation Parameters, based on optical astrometry and catalog EOC-4.
Implementation of the IAU 2000 definition of UT1 in astronomy
Authors: Capitaine Nicole , Wallace Patrick T.
Published: October 2010

We recall the concepts and nomenclature associated with the IAU 2000 definition of UT1 as function of the Earth rotation angle (ERA). We comment on the complications that arise when UT1 is regarded as both an angle and a time scale. We review the IAU 2006 expressions for the position of the celestial intermediate origin (CIO) and the equation of the origins, and the associated CIO and equinox based procedures for the celestial-to-terrestrial transformation.
Impact of Geophysical Fluids on UT1
Authors: Gross Richard S.
Published: October 2010

Geophysical fluids have a major impact on the Earth's rotation. Tidal variations within the oceans are the predominant cause of subdaily length-of-day (lod) variations while those within the solid body of the Earth are a major source of longer period variations; tidal dissipation within the solid Earth and oceans cause a secular change in lod. Fluctuations of the atmospheric winds are the predominant cause of nontidal lod variations on sub-decadal time scales while decadal variations are caused by interactions between the fluid core and mantle.
Short-term tidal variations in UT1: compliance between modelling and observation
Authors: Englich Sigrid , Schuh Harald , Weber Robert
Published: October 2010

The Earth rotation rate and consequently universal time (UT1) and length of day (LOD) are periodically affected by solid Earth tides and oceanic tides. Solid Earth tides induce changes with periods from around 5 days to 18.6 years, with the largest amplitudes occurring at fortnightly, monthly, semi-annual and annual periods, and at 18.6 years. The principal variations caused by oceanic tides have diurnal and semi-diurnal periods. For the investigation of the tidal effects with periods of up to 35 days, UT1 series are estimated from VLBI observation data of the time interval 1984–2008. The amplitudes and phases of the terms of interest are calculated and the results for diurnal and sub-diurnal periods are compared and evaluated with tidal variations derived from a GNSS-based LOD time series of 8 months. The observed tidal signals are finally compared to the predicted tidal variations according to recent geophysical models.
Current Status and Future Directions of the IERS RS/PC Predictions of UT1
Authors: Wooden W. , Luzum B. , Stamatakos N.
Published: October 2010

The International Earth Rotation and Reference Systems Service (IERS) Rapid Service/Prediction Center (RS/PC) produces daily and weekly EOP combination and prediction solutions. The daily solutions are produced after 1700 UTC while the weekly EOP solutions are produced Thursday after 1700 UTC. These solutions include data from Atmospheric Angular Momentum (AAM) analysis and forecasts, Global Positioning System (GPS) solutions, Satellite Laser Ranging (SLR) solutions, and Very Long Baseline Interferometry (VLBI) solutions. The solutions are sent to roughly 700 people by e-mail per week and are picked up in roughly 40000 ftp downloads per month.
Time Ephemeris and General Relativistic Scale Factor
Authors: Fukushima Toshio
Published: October 2010

Time ephemeris is the location-independent part of the transformation formula relating two time coordinates such as TCB and TCG (Fukushima 2009). It is computed from the corresponding (space) ephemerides providing the relative motion of two spatial coordinate origins such as the motion of geocenter relative to the solar system barycenter. The time ephemerides are inevitably needed in conducting precise four dimensional coordinate transformations among various spacetime coordinate systems such as the GCRS and BCRS (Soffel et al. 2003). Also, by means of the time average operation, they are used in determining the information on scale conversion between the pair of coordinate systems, especially the difference of the general relativistic scale factor from unity such as LC. In 1995, we presented the first numerically-integrated time ephemeris, TE245, from JPL's planetary ephemeris DE245 (Fukushima 1995). It gave an estimate of LC as 1.4808268457(10) × 10−8, which was incorrect by around 2 × 10−16. This was caused by taking the wrong sign of the post-Newtonian contribution in the final summation. Four years later, we updated TE245 to TE405 associated with DE405 (Irwin and Fukushima 1999). This time the renewed vale of LC is 1.48082686741(200) × 10−8 Another four years later, by using a precise technique of time average, we improved the estimate of Newtonian part of LC for TE405 as 1.4808268559(6) × 10−8 (Harada and Fukushima 2003). This leads to the value of LC as LC = 1.48082686732(110) × 10−8. If we combine this with the constant defining the mean rate of TCG-TT, LG = 6.969290134 × 10−10 (IAU 2001), we estimate the numerical value of another general relativistic scale factor LB = 1.55051976763(110) × 10−8, which has the meaning of the mean rate of TCB-TT. The main reasons of the uncertainties are the truncation effect in time average and the uncertainty of asteroids' perturbation. As a compact realization of the time ephemeris, we prepared HF2002, a Fortran routine to compute approximate harmonic series of TE405 with the RMS error of 0.446 ns for the period 1600 to 2200 (Harada and Fukushima 2003). It is included in the IERS Convention 2003 (McCarthy and Petit 2003) and available from the IERS web site; http://tai.bipm.org/iers/conv2003/conv2003_c10.html.
Atomic time scales TAI and TT(BIPM): present performances and prospects
Authors: Petit Gérard
Published: October 2010

We review the stability and accuracy achieved by the reference atomic time scales TAI and TT(BIPM). We show that they presently are at the level of a few 10−16in relative value, based on the performance of primary standards, of the ensemble time scale and of the time transfer techniques. We consider how the 1 × 10−16value could be reached or superseded and which are the present limitations to attain this goal.
Impact of new frequency standards on the international time scales
Authors: Arias E. Felicitas , Panfilo Gianna
Published: October 2010

The reference time scales maintained at the International Bureau of Weights and Measures (BIPM) are constructed with data from industrial clocks and primary frequency standards operated in national metrology laboratories and observatories world-wide distributed. Clocks are compared making use of techniques of time transfer between remote sites. The algorithm of calculation relies on clock weighting and clock frequency prediction. We briefly present hereafter the influence of some clocks on the scales, as well as the possibilities for improvement.
VLBI Measurements for Frequency Transfer
Authors: Takiguchi Hiroshi , Koyama Yasuhiro , Ichikawa Ryuichi , Gotoh Tadahiro , Ishii Atsutoshi , Hobiger Thomas , Hosokawa Mizuhiko
Published: October 2010

We carried out the intercomparison experiments between VLBI, GPS and DMTD to show the VLBI can measure the right time difference. We produced the artificial change using by line stretcher. At the artificial change part, VLBI and DMTD show good agreement, less than 10ps. The quantity and sense of VLBI results match well with DMTD results. Consequently, the geodetic VLBI technique can measure the right time difference.
Pulsar glitches detected at Urumqi
Authors: Wang N.
Published: October 2010

We present an analysis of glitches detected at Urumqi from 2000 to 2008. Statistics based on all known glitches, for example post glitch behavior were investigated.
Search for ultra-long gravitational waves in pulsars' rotational parameters
Authors: Pshirkov Maxim S.
Published: October 2010

A method is suggested to explore the gravitational wave background (GWB) in the frequency range from 10−12 to 10−8 Hz. That method is based on the precise measurements of pulsars' rotational parameters: the influence of the gravitational waves (GW) in the range will affect them and therefore some conclusions about energy density of the GWB can be made using analysis of the derivatives of pulsars' rotational frequency. The calculated values of the second derivative from a number of pulsars limit the density of GWB Ωgw as follows: Ωgwh2 < 10−6. Also, the time series of the frequency ν of different pulsars in pulsar array can be cross-correlated pairwise in the same manner as in anomalous residuals analysis thus providing the possibility of GWB detection in ultra-low frequency range.
The Parkes Pulsar Timing Array Project
Authors: Manchester R. N.
Published: October 2010

The Parkes Pulsar Timing Array project is timing 20 millisecond pulsars with the aims of detecting gravitational waves, establishing a time scale based on pulsar periods and improving solar-system ephemerides.
JD7 -Astrophysical Outflows and Associated Accretion Phenomena
Authors: de Gouveia Dal Pino Elisabete M. , Raga Alex C.
Published: October 2010

Highly collimated supersonic jets and outflows are very frequent in several astrophysical environments. They are seen in young stellar objects (YSOs), proto-planetary nebulae, compact objects (like galactic black holes or microquasars, and X-ray binary stars), active galactic nuclei, and are also possibly associated to gamma-ray bursts (GRBs) and to ultra-high energy cosmic rays sources (UHECRs). Despite their different physical scales, all these outflow classes have strong morphological similarities, but questions such as - what physics do they share? - or - can we find a universal mechanism of acceleration and collimation that operates in all classes? - remain matters of debate. The most accepted mechanism for their origin relies on a rotating accretion disk threaded by perpendicular large-scale magnetic fields and, though most of the systems producing jets contain an accretion disk around the central source, the real role that rotation and magnetic fields play in these processes is still not fully understood, nor are the highly non-linear physical processes connected to these jet-disk systems in the large parameter space involved.
Numerical Simulations of MHD Accretion Disks
Authors: Hawley J. F.
Published: October 2010

Numerical simulations play an increasingly important role in investigating accretion disks and associated phenomena such as jets. This paper provides a few examples of recent results that have been obtained with simulations, both local or global.
QPO-jet relation in X-ray binaries
Authors: Belloni Tomaso M.
Published: October 2010

In the past years, a clear picture of the evolution of outbursts of black-hole X-ray binaries has emerged. While the X-ray properties can be classified into our distinct states, based on spectral and timing properties, the observations in the radio band have shown strong links between accretion and ejection properties. Here I briefly outline the association between X-ray timing and jet properties.
Are jets rotating at the launching?
Authors: Soker Noam
Published: October 2010

I argue that the Doppler shift asymmetries observed in some young stellar object (YSO) jets result from the interaction of the jets with the circumstellar gas, rather than from jets' rotation. The jets do rotate, but at a velocity much below claimed values. During the meeting I carefully examined new claims, and found problems with the claimed jets' rotation. I will challenge any future observation that will claim to detect jet rotation in YSOs that requires the jets (and not a wind) to be launched from radii much larger than the accreting stellar radius. I conclude that the most likely jets' launching mechanism involves a very efficient dynamo in the inner part of the accretion disk, with a jets' launching mechanism that is similar to solar flares (coronal mass ejection).
High Resolution 3D Relativistic MHD Simulations of Jets
Authors: Ferrari A. , Mignone A. , Rossi P. , Bodo G. , Massaglia S.
Published: October 2010

We performed high-resolution three dimensional numerical simulations of relativistic MHD jets carrying an initially toroidal magnetic field responsible for the process of jet acceleration and collimation. We find that in the 3D case the toroidal field gives rise to strong current driven kink instabilities leading to jet wiggling. However, it appears to be able to maintain an highly relativistic spine along its full length.
Variable jets from young stars
Authors: Raga A. C. , Cantó J. , Esquivel A. , Rodríguez-González A. , Velázquez P. F.
Published: October 2010

In this paper we discuss the fact that the observed “accelerations” (i. e., higher velocities at larger distances from the source) observed along some Herbig-Haro (HH) jets directly imply that the ejection velocity has to be time-dependent. Even though discussed in the early literature of the subject, this is an often forgotten fact.
Radio and Millimeter Observations of YSOs
Authors: Rodríguez Luis F.
Published: October 2010

The growth of a forming star takes place by accretion from the surrounding dense medium, facilitated by a circumstellar disk. But at the same time the forming system produces collimated outflows of gas that remove excess angular momentum and magnetic flux. A key question in the field is whether we can extend the disk/jet model to stars of the largest masses or if other ingredients are present. In this note, I review recent observations from the Very Large Array and the Submillimeter Array, of IRAS 16547-4247, a massive young stellar object that exhibits evidence for both a disk and an outflow.
XMM-Newton observations of elliptical galaxies in the local universe
Authors: Trinchieri Ginevra
Published: October 2010

XMM-Newton is well suited to the study of the X-ray properties of early-type galaxies: the wide energy band allows a characterization of the different components of the X-ray emission in galaxies, separating the gas from the compact source component through their spectral characteristics, and identifying low-luminosity absorbed AGNs; the large field of view allows a proper understanding of the large scale emission, and the separation between the galaxy and the surrounding group. Nonetheless, in spite of the much improved understanding of the X-ray characteristics of this class of sources, much of the original questions on the global X-ray properties of early-type galaxies remain. One in particular: how can we predict how much gas is there in any given galaxy? We have learned that the individual sources are tightly linked to the stellar component, both field stars and relative frequency of globular clusters. We have also learned that the central group galaxies, brighter and more extended, might represent a specific class of early-type galaxies, rather than the population as a whole. Yet we have not learned how to predict, from the stellar properties, how much hot gas a galaxy will have. Even a well selected class of sources, namely early type galaxies in isolation, where we can exclude the influence of the environment, appear to retain different amounts of the hot ISM produced by the stellar population, and display a wide range of Lx for their gaseous component for a relative narrow range of Lb, or mass [measured through LK], as shown by Fig. 1.
Hyperfine structure radio lines from hot ISM in elliptical galaxies
Authors: Docenko Dmitrijs , Sunyaev Rashid A.
Published: October 2010

Hyperfine structure (HFS) line of 14N VII ion with rest frequency of ν = 53.04 GHz should be detectable from the interstellar medium in some of the densest and coolest cores of elliptical galaxies at redshifts exceeding 0.15 or so.
Cool gas in brightest cluster galaxies
Authors: Oonk J. B. R. , Jaffe W. , Bremer M. N. , Hatch N.
Published: October 2010

Gas in galaxy clusters requires re-heating. We study the re-heating of the cool gas phases. Ionized and molecular gas is traced out to 20 kpc and found to be strongly coupled. The observed line emission may in part be explained by excitation due to hot, young stars.
A multi-instrument comparison of the hot ISM in elliptical galaxies
Authors: Bregman Joel N.
Published: October 2010

Consistent metallicities are now obtained in X-ray bright galaxies, using the Chandra ACIS and XMM PN, MOS and RGS detectors. With two temperature models, the Fe metallicity of the gas is typically solar, similar to Mg, Si, and S, but the O abundance is about half solar. These values are in conflict with models, which predict a metallicity 3-5 times higher and a Fe to O ratio near unity. This suggests that a significant fraction of metals are not becoming mixed into the hot galactic atmosphere.
Abundance ratios in stars vs. hot gas in elliptical galaxies
Authors: Pipino Antonio
Published: October 2010

I present predictions from a chemical evolution model for a self-consistent study of optical (i.e., stellar) and X-ray (i.e., gas) properties of present-day elliptical galaxies. Detailed cooling and heating processes in the interstellar medium are taken into account and allow a reliable modelling of the SN-driven galactic wind. The model simultaneously reproduces the mass-metallicity, colour-magnitude, LX - LB and LX - T relations, and the observed trend of [Mg/Fe] with σ. The "iron discrepancy" can be solved by taking into account the dust presence.
Metal abundances in the hot ISM of early-type galaxies
Authors: Humphrey Philip J. , Buote David A.
Published: October 2010

Understanding the process of metal enrichment is one of the key problems for our picture of structure formation and evolution, in which early-type galaxies are a crucial ingredient. X-ray observations provide a powerful tool for measuring the metal distributions in their hot ISM, which is shaped by their entire history of star-formation, evolution and feedback. In Fig 1 (left panel), we summarize the results of a Chandra survey of metals in early-type galaxies, supplemented with Suzaku data (Humphrey & Buote 2006, P. Humphrey et al., in prep.). Chandra is particularly suited to this study, as it enables temperature gradients and X-ray point sources to be resolved, mitigating two important sources of bias (e.g., Buote & Fabian 1998; Fabbiano et al. 1994). We found on average that the ISM is at least as metal-rich as the stars, and we did not find the problematical, highly sub-solar, abundances historically reported. The abundance ratios of O, Ne, Mg, Si and S with respect to Fe are similar to the centres of massive groups and clusters, suggesting homology in the enrichment process over a wide mass range. Finally, using high-quality Suzaku data, we were able to resolve, for the first time in a galaxy-scale (≲1013M⊙) object, a radial abundance gradient similar to those seen in some bright galaxy groups (Fig. 1, right panel).
Fossil groups of galaxies: Are they groups? Are they fossils?
Authors: Dupke Renato de Alencar , Miller Eric , de Oliveira Claudia Mendes , Sodre Laerte , Rykoff Eli , de Oliveira Raimundo Lopes , Proctor Rob
Published: October 2010

Fossil groups present a puzzle to current theories of structure formation. Despite the low number of bright galaxies, their high velocity dispersions and high TX indicate cluster-like potential wells. Measured concentration parameters seem very high indicating early formation epochs in contradiction with the observed lack of large and well defined cooling cores. There are very few fossil groups with good quality X-ray data and their idiosyncrasies may enhance these apparent contradictions. The standard explanation for their formation suggests that bright galaxies within half the virial radii of these systems were wiped out by cannibalism forming the central galaxy. Since dry mergers, typically invoked to explain the formation of the central galaxies, are not expected to change the IGM energetics significantly, thus not preventing the formation of cooling cores, we investigate the scenario where recent gaseous (wet) mergers formed the central galaxy injecting energy and changing the chemistry of the IGM in fossil groups. We show a test for this scenario using fossil groups with enough X-ray flux in the Chandra X-ray Observatory archive by looking at individual metal abundance ratio distributions near the core. Secondary SN II powered winds would tend to erase the dominance of SN IA ejecta in the core of these systems and would help to erase previously existing cold cores. Strong SN II-powered galactic winds resulting from galaxy merging would be trapped by their deep potential wells reducing the central enhancement of SN Ia/SN II iron mass fraction ratio. The results indicate that there is a decrement in the ratio of SN Ia to SN II iron mass fraction in the central regions of the systems analyzed, varying from 99±1% in the outer regions to 85±2% within the cooling radius (Figure 1) and would inject enough energy into the IGM preventing central gas cooling. The results are consistent with a scenario of later formation epoch for fossil groups, as they are defined, when compared to galaxy clusters and normal groups.
A large X-ray sample of fossil groups
Authors: Miller Eric D. , Rykoff Eli , Dupke Renato de Alencar , de Oliveira Claudia Mendes , McKay Timothy , Koester Benjamin
Published: October 2010

We present Chandra snapshot observations of the first large X-ray sample of optically identified fossil groups. For 9 of 14 candidate groups, we are able to determine the X-ray luminosity and temperature, which span a range typical of large ellipticals to rich groups of galaxies. We discuss these initial results in the context of group IGM and central galaxy ISM evolution, and we also describe plans for a deep X-ray follow-up program.
AGN feedback in numerical simulations
Authors: Ciotti Luca
Published: October 2010

The passively evolving stellar population in elliptical galaxies (Es) provides a continuous source of fuel for accretion on the central supermassive black hole (SMBH), which is 1) extended over the entire galaxy life (but declining with cosmic time), 2) linearly proportional to the stellar mass of the host spheroid, 3) summing up to a total gas mass that is > 100 times larger than the currently observed SMBH masses, 4) available independently of merging events. The main results of numerical simulations of Es with central SMBH, in which a physically based implementation of radiative and mechanical feedback effects is considered, are presented.
Constraints on turbulent pressure in the X-ray halos of giant elliptical galaxies from resonant scattering
Authors: Werner Norbert , Zhuravleva Irina , Churazov Eugene , Simionescu Aurora , Allen Steve W. , Forman William , Jones Christine , Kaastra Jelle
Published: October 2010

The dense cores of X-ray emitting gaseous halos of large elliptical galaxies with temperatures below about 0.8 keV show two prominent Fe XVII emission features, which provide a sensitive diagnostic tool to measure the effects of resonant scattering. We present here high-resolution spectra of five bright nearby elliptical galaxies, obtained with the Reflection Grating Spectrometers (RGS) on the XMM-Newton satellite. The spectra for the cores of four of the galaxies show the Fe XVII line at 15.01 Angstrom being suppressed by resonant scattering. The data for NGC 4636 in particular allow the effects of resonant scattering to be studied in detail. Using deprojected density and temperature profiles for this galaxy obtained with the Chandra satellite, we model the radial intensity profiles of the strongest resonance lines, accounting for the effects of resonant scattering, for different values of the characteristic turbulent velocity. Comparing the model to the data, we find that the isotropic turbulent velocities on spatial scales smaller than about 1 kpc are less than 100 km/s and the turbulent pressure support in the galaxy core is smaller than 5% of the thermal pressure at the 90% confidence level, and less than 20% at 99% confidence. Neglecting the effects of resonant scattering in spectral fitting of the inner 2 kpc core of NGC 4636 will lead to underestimates of the chemical abundances of Fe and O by about 10-20%.
Thermodynamics in Variable Speed of Light Theories
Authors: Racker Juan , Sisterna Paolo , Vucetich Hector
Published: October 2010

Variable speed of light theories (VSL) are interesting because they could solve several cosmological puzzles. In this work we study the thermodynamics and Newtonian limit of the varying speed of light theory developed by J. Magueijo (Magueijo 2000). In the covariant and locally Lorentz invariant VSL proposed by Magueijo c is a dimensionless dynamical scalar field c=c0eψ, where c0 is a constant. The matter and gravitational lagrangians are multiplied by the factors ebψ and eaψ respectively.
Accelerating universe and the time-dependent fine-structure constant
Authors: Fujii Yasunori
Published: October 2010

I start with assuming a gravitational scalar field as the dark-energy supposed to be responsible for the accelerating universe. Also from the point of view of unification, a scalar field implies a time-variability of certain “constants” in Nature. In this context I once derived a relation for the time-variability of the fine-structure constant α: Δα/α =ζ Ƶ(α/π) Δσ, where ζ and Ƶ are the constants of the order one, while σ on the right-hand side is the scalar field in action in the accelerating universe. I use the reduced Planckian units with c=ℏ =MP(=(8π G)−1/2)=1. I then compared the dynamics of the accelerating universe, on one hand, and Δα/α derived from the analyses of QSO absorption lines, Oklo phenomenon, also different atomic clocks in the laboratories, on the other hand. I am here going to discuss the theoretical background of the relation, based on the scalar-tensor theory invented first by Jordan in 1955.
Searching for space-time variation of the fine structure constant using QSO spectra: overview and future prospects
Authors: Berengut J. C. , Dzuba V. A. , Flambaum V. V. , King J. A. , Kozlov M. G. , Murphy M. T. , Webb J. K.
Published: October 2010

Current theories that seek to unify gravity with the other fundamental interactions suggest that spatial and temporal variation of fundamental constants is a possibility, or even a necessity, in an expanding Universe. Several studies have tried to probe the values of constants at earlier stages in the evolution of the Universe, using tools such as big-bang nucleosynthesis, the Oklo natural nuclear reactor, quasar absorption spectra, and atomic clocks (see, e.g. Flambaum & Berengut (2009)).
The effects of coupling variations on BBN
Authors: Olive Keith A.
Published: October 2010

The effect of variations of the fundamental nuclear parameters on big-bang nucleosynthesis are modeled and discussed in detail taking into account the interrelations between the fundamental parameters arising in unified theories. Considering only 4He, strong constraints on the variation of the neutron lifetime, neutron-proton mass difference are set. We show that a variation of the deuterium binding energy is able to reconcile the 7Li abundance deduced from the WMAP analysis with its spectroscopically determined value while maintaining concordance with D and 4He.
Constraints on the variations of fundamental couplings by stellar models
Authors: Coc A. , Ekström S. , Descouvemont P. , Vangioni E.
Published: October 2010

The effect of variations of the fundamental constants on the thermonuclear rate of the triple alpha reaction, 4He(αα,γ)12C, that bridges the gap between 4He and 12C is investigated. We follow the evolution of 15 and 60 M⊙ zero metallicity star models, up to the end of core helium burning. They are assumed to be representative of the first, Population III stars undergoing a very peculiar evolution due to the absence of initial CNO elements (zero metallicity). The calculated oxygen and carbon abundances resulting from helium burning can then be used to constrain the variations of the fundamental constants.
WMAP 5-year constraints on α and me
Authors: Scóccola Claudia G. , Landau Susana J. , Vucetich Héctor
Published: October 2010

We have studied the role of fundamental constants in an updated recombination scenario. We focus on the time variation of the fine structure constant α, and the electron mass me in the early Universe. In the last years, helium recombination has been studied in great detail revealing the importance of taking new physical processes into account in the calculation of the recombination history. The equations to solve the detailed recombination scenario can be found for example in Wong et al. 2008. In the equation for helium recombination, a term which accounts for the semi-forbidden transition 23p–11s is added. Furthermore, the continuum opacity of HI is taken into account by a modification in the escape probability of the photons that excite helium atoms, with the fitting formulae proposed Kholupenko et al 2007. We have analized the dependences of the quantities involved in the detailed recombination scenario on α and me. We have performed a statistical analysis with COSMOMC to constrain the variation of α and me at the time of neutral hydrogen formation. The observational set used for the analysis was data from the WMAP 5-year temperature and temperature-polarization power spectrum and other CMB experiments such as CBI, ACBAR and BOOMERANG and the power spectrum of the 2dFGRS. Considering the joint variation of α and me we obtain the following bounds: -0.011 < $\frac{Δ α}{α_0}$ < 0.019 and -0.068 < $\frac{Δ m_e}{(m_e)_0$ < 0.030 (68% c.l.). When considering only the variation of one fundamental constant we obtain: -0.010 < $\frac{Δ α}{α_0$ < 0.008 and -0.04 < $\frac{Δ m_e}{(m_e)_0}$ < 0.02 (68% c.l.). We compare these results with the ones presented in Landau et al 2008, which were obtained in the standard recombination scenario and using WMAP 3 year release data. The constraints are tighter in the current analysis, which is an expectable fact since we are working with more accurate data from WMAP. The bounds obtained are consistent with null variation, for both α and me, but in the present analysis, the 68% confidence limits on the variation of both constants have changed. In the case of α, the present limit is more consistent with null variation than the previous one, while in the case of me the single parameters limits have moved toward lower values. To study the origin of this difference, we have performed another statistical analysis, namely the analysis of the standard recombination scenario together with WMAP5 data, the other CMB data sets and the 2dFGRS power spectrum. We see that the change in the obtained results is due to the new WMAP data set, and not to the new recombination scenario. The obtained results for the cosmological parameters are in agreement within 1 σ with the ones obtained by the WMAP collaboration, without considering variation of fundamental constants.
Will cosmic acceleration last forever?
Authors: Alcaniz J. S.
Published: October 2010

Although the transition from an initially decelerated to a late-time accelerating cosmic expansion is becoming observationally established, the duration of the accelerating phase depends on the cosmological scenario and, several models, which includes our standard one, imply an eternal acceleration or even an accelerating expansion until the onset of a future cosmic singularity. In this regard, an interesting theoretical question arises if one tries to reconcile the standard description of the current cosmic acceleration with the only candidate for a consistent quantum theory of gravity we have today, i.e., Superstring theory.
Spatial and temporal variations of fundamental constants
Authors: Levshakov S. A. , Agafonova I. I. , Molaro P. , Reimers D.
Published: October 2010

Spatial and temporal variations in the electron-to-proton mass ratio, μ, and in the fine-structure constant, α, are not present in the Standard Model of particle physics but they arise quite naturally in grant unification theories, multidimensional theories and in general when a coupling of light scalar fields to baryonic matter is considered. The light scalar fields are usually attributed to a negative pressure substance permeating the entire visible Universe and known as dark energy. This substance is thought to be responsible for a cosmic acceleration at low redshifts, z < 1. A strong dependence of μ and α on the ambient matter density is predicted by chameleon-like scalar field models. Calculations of atomic and molecular spectra show that different transitions have different sensitivities to changes in fundamental constants. Thus, measuring the relative line positions, Δ V, between such transitions one can probe the hypothetical variability of physical constants. In particular, interstellar molecular clouds can be used to test the matter density dependence of μ, since gas density in these clouds is ~15 orders of magnitude lower than that in terrestrial environment. We use the best quality radio spectra of the inversion transition of NH3 (J,K)=(1,1) and rotational transitions of other molecules to estimate the radial velocity offsets, Δ V ≡ Vrot - Vinv. The obtained value of Δ V shows a statistically significant positive shift of 23±4stat±3sys m s−1 (1σ). Being interpreted in terms of the electron-to-proton mass ratio variation, this gives Δμ/μ = (22±4stat±3sys)×10−9. A strong constraint on variation of the quantity F = α2/μ in the Milky Way is found from comparison of the fine-structure transition J=1-0 in atomic carbon C i with the low-J rotational lines in carbon monoxide 13CO arising in the interstellar molecular clouds: |Δ F/F| < 3×10−7. This yields |Δ α/α| < 1.5×10−7 at z = 0. Since extragalactic absorbers have gas densities similar to those in the ISM, the values of |Δ α/α| and |Δ μ/μ| at high-z are expected to be at the same level as estimated in the Milky Way providing no temporal dependence of α and μ is present. We re-analyzed and reviewed the available optical spectra of quasars to probe Δα/α from intervening absorbers. The Fe i system at z = 0.45 towards HE 0000–2340 provides one of the best opportunities for precise measurements of Δα/α at low redshift. The current estimate is Δα/α = (7±7)×10−6. With the updated sensitivity coefficients for the Fe ii lines we re-analyzed the z = 1.84 system from the high-resolution UVES/VLT spectrum of Q 1101–264 (FWHM = 3.8 km s−1) and found Δα/α = (4.0±2.8)×10−6. The most accurate upper limit on cosmological variability of α is obtained from the Fe ii system at z = 1.15 towards the bright quasar HE 0515–4414 (V=14.9): Δα/α = (-0.12±1.79)×10−6, or |Δα/α| < 2×10−6. The limit of 2×10−6 corresponds to the utmost accuracy which can be reached with available to date optical facilities.
Searching for places where to test the variations of fundamental constants
Authors: Petitjean P. , Noterdaeme P. , Srianand R. , Ledoux C. , Ivanchik A. , Gupta N.
Published: October 2010

It has been realised in the last few years that strong constraints on the time-variations of dimensionless fundamental constants of physics can be derived at any redshift from QSO absorption line systems. Variations of the fine structure constant, α, the proton-to-electron mass ratio, μ, or the combination, x=α2gp/μ, where gp is the proton gyromagnetic factor, have been constrained. However, for the latter two constants, the number of lines of sight where these measurements can be performed is limited. In particular the number of known molecular and 21 cm absorbers is small. Our group has started several surveys to search for these systems. Here is a summary of some of the characteristics of these absorbers that can be used to find these systems.
New limit on a varying proton-to-electron mass ratio from high-resolution optical quasar spectra
Authors: Malec A. L. , Buning R. , Murphy M. T. , Milutinovic N. , Ellison S. L. , Prochaska J. X. , Kaper L. , Tumlinson J. , Carswell R. F. , Ubachs W.
Published: October 2010

Molecular transitions recently discovered at redshift zabs=2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-electron mass ratio, μ ≡ mp/me. Observed with the Keck telescope, the optical spectrum has the highest resolving power and largest number (86) of H2 transitions in such analyses so far. Also, (7) HD transitions are used for the first time to constrain μ-variation. These factors, and an analysis employing the fewest possible free parameters, strongly constrain μ's relative deviation from the current laboratory value: Δμ/μ =(+5.6±5.5stat±2.7sys)×10−6. This is the first Keck result to complement recent constraints from three systems at zabs>2.5 observed with the Very Large Telescope.
VLT and E-ELT spectrographs & fundamental-constants
Authors: Molaro Paolo
Published: October 2010

The fundamental dimensionless physical constants cannot be predicted by theory but can only be measured experimentally. And so it is of their possible variation where there are several theoretical predictions but unfortunately with little theoretical guidance on the expected rate of change. The role of fundamental constants in the representation of nature as well as the implications of their variability for the Equivalence Principle and cosmology have been highlighted in many contributions at this conference (cfr K. Olive and J.P Uzan, these proceedings). Measuring the variability of the fine structure constant α or the electron-to-proton ratio μ by means of absorption lines implies the measurement of a tiny variation of the position of one or a few lines with regard to other lines which are taken as reference. For the fine structure constant the relation between its change and the doppler velocity shift is: