bluuebunny/crossref_metadata_2025 huggingface dataset:
Space astrometry prospects and limitations
Authors: Kovalevsky J. , Mignard F. , Froeschlé M.
Published: June 2019

Among the few parameters that describe the generalized space time metrics, astrometric techniques are essentially sensitive to the displacement of the apparent positions of celestial bodies. This includes the relativistic light deflection and aberration. The possibilities of small field and wide field astrometry in measuring these effects are described. The case of the second order aberration terms is considered with some detail from the theoretical point of view, both for stellar and planetary aberration. New results are presented in the latter case.

A section is devoted to a description of the existing space astrometry projects among which Space Telescope and HIPPARCOS are approved but will not contribute significantly to relativistic studies. Several “second generation” projects exist that aim at 2 or 3 orders of magnitude improvement in precision. They would yield results on second order relativistic effects and may be used to determine masses of some single stars. However, the present state of engineering of space astrometric missions has permitted to identify several limitations of the present and future missions. They will not all be readily suppressed and one should be very careful in assessing now their potentialities. It seems however that interferometric techniques have more chance to reach the 10−4and 10−5arc second precision than the imaging methods.
HI Rotation Curves of Galaxies
Authors: Sancisi R. , van Albada T. S.
Published: June 2019

The observational evidence on the discrepancy between the mass distribution in galaxies derived from HI rotation curves and that derived from the distribution of light is reviewed. In the outer parts the discrepancy is such that in some galaxies there is at least three times as much dark matter as luminous matter. This is a direct consequence of the nearly constant circular velocity far beyond the edge of the visible part of the galaxy, as derived from the motion of HI. The discrepancy is clearly present already near the edge of the visible disk (R25). In the inner regions, i.e. inside approximately 2.5 disk scale-lengths, no dark matter is required, but its presence can not be ruled out. There is no evidence for a dependence on galaxy luminosity or morphological type. These results suggest a strong coupling between luminous matter and dark matter within individual galaxies, and among galaxies as well. Finally attention is drawn to the large-scale asymmetries in the outer parts of galaxies and to possible implications for the vertical distribution of dark matter.
About the Coma Cluster (Progress Report)
Authors: Gerbal D. , Mathez G. , Mazure A. , Salvadore-Solé E.
Published: June 2019

The study of the dynamics of the Coma Cluster is of interest for several reasons. First, there exists a great deal of observational information about the cluster, including data on morphology, magnitude, color and redshift for the galaxies, and reasonably detailed x-ray data for the hot gas. Second, the present dynamical state of the cluster is reasonably well-defined. In addition, the segregation of the more luminous (≡ massive) galaxies towards the cluster center shows that two-body relaxation effects are well-advanced (Capelato et al. 1980). The profile of velocity dispersion with radius shows that in the outer parts of the cluster the galaxy velocities are non-isothermal (des Forêts et al. 1984). There is, however, evidence of continuing dynamical evolution. The velocity field of the galaxies at large distances from the center of the cluster suggests continuing infall (Capelato et al. 1982), and two sub-condensations are located in the inner regions (Mazure and Proust 1986). A new dynamical analysis for the cluster is being carried out in two stages. First, a relaxed model with a wide mass spectrum (c.f. Inagaki 1980) is fitted to the data. The contribution of the intergalactic gas is taken into account. With HO = 75 km/sec/Mpc, the total mass within a 3° radius of the center is ∼ 1.5 × 1015 M⊙, of which ∼ 30% is in the intergalactic medium, and M/L ∼ 75 M⊙/L⊙. The ratio of specific energies of the galaxies and the gas is ∼ 1.1, i.e., there is no scale-height problem (these results are described more fully by Gerbal et al. 1986). A second “model independent” analysis using the profiles of the galactic density and velocity dispersion gives the radial dependence of the galactic mass, the gas mass and also gives the total mass, which is found to be ∼ 1.1 × 1015 M⊙ within 3° (Gerbal et al. 1984).
Dynamical Interaction between the Different Components of SO-SD Galaxies
Authors: Bacon R. , Martinet L.
Published: June 2019

Using both photometric and gas kinematic data of three galaxies of different type (NGC 7814 SO, NGC 2841 Sb, NGC 300 Sd), we estimate the density of the dark halo and visible components which gives the best fit with the observed rotation curves. We then compute the ratio of each component force to the total force as function of radius. Finally, we derive from the potential energy tensor the quantitative effect of each component on bulge, disk and halo dynamics.
The Evaporation of Strange Matter in the Early Universe
Authors: Alcock Charles , Farhi Edward
Published: June 2019

A new candidate for the dark matter of the universe is strange matter. This substance consists of roughly equal numbers of up, down and strange quarks confined in a quark phase which is conjectured to have a lower energy per baryon number than ordinary nuclei. Strange matter is absolutely stable, has a density comparable to that of nuclei and can exist in lumps ranging in size from a few fermis to ∼ 10 km. If it is distributed in space in lumps larger than ∼ 1 cm, it could close the universe without ever encountering the earth and would be astronomically unobservable.
Conference Summary
Authors: Gunn James E.
Published: June 2019

I will attempt in this talk to address the questions that Drs. Schwarzschild and Faber posed at the beginning, in the light of what has been said in the last few days and a few things that were not but perhaps should have been.
Measurements of solar internal rotation obtained with the Mt. Wilson 60-foot solar tower
Authors: Rhodes Edward J. , Cacciani Alessandro , Woodard Martin , Tomczyk Steven , Korzennik Sylvain , Ulrich Roger K.
Published: June 2019

We have obtained estimates of the solar internal rotational velocity from measurements of the frequency splittings of p-mode oscillations. Specifically, we have analyzed a 10-day time series of full-disk Dopplergrams obtained during July and August 1984 at the 60-Foot Tower Telescope of the Mt. Wilson Observatory. The Dopplergrams were obtained with a Na magneto-optical filter and a 244 × 248-pixel CID camera. From the time series we computed power spectra for all of the prograde and retrograde sectoral p-modes from ℓ = 0 to 200 and for all of the tessaral harmonics up to ℓ = 89. We then applied a cross-correlation analysis to the resulting sectoral power spectra to obtain estimates of the frequency splittings. From ℓ = 4 to ℓ = 30 we obtained a mean value of the frequency spitting of roughly 450 nHz (sidereal) in close agreement with most previously published results, while from ℓ = 40 to ℓ = 140 we obtained a mean value of about 470 nHz. We believe that the latter value is slightly higher than the surface rotational splitting of 461 nHz because of possible confusion due to the temporal sidelobes introduced by the day/night observing cycle. Confirmation of this possibility will have to await our computation of tesseral power spectra for degrees greater than our current limit of 89. Finally, for degrees between 140 and 200, the frequency splittings are indistinguishable from the surface rotation rate.
Ground based observations of solar luminosity oscillations
Authors: Andersen B. N. , Domingo V.
Published: June 2019

Results from ground based observations of low degree solar luminosity variations are presented. By using data from up to 15 consecutive excellent days the majority of the 1=0, 1 and 2 peaks in the region 2.5–3.5 mHz may marginally be identified.
Solar gravity modes from ACRIM/SMM irradiance data
Authors: Fröhlich Claus
Published: June 2019

Solar irradiance data from the ACRIM solar constant experiment on board the Solar Maximum Mission satellite (SMM) have been used to search for solar gravity modes. The power spectra of the time series of 270 days in 1980 and of 240 days in 1984 are analysed using a statistical method for the determination of the basic g-mode period separation To and the rotational frequency vR. In the view of the proposal of weakly interacting massive particles (WIMP) in the solar core and their impact on To the search has been extended down to 25 minutes. The results of the analysis of both time series in the frequency range from 10 to 40 μHz are best fitted by a To of 29.85 minutes. This is close to the expected value for the WIMP model. The angular velocity in the center of the Sun inferred from the rotational splitting of the g-modes amounts to 6.6·10−6 per sec, which is 2.3 times the photospheric rate.
The influence of a modified mixing-length theory and of an adopted description of the atmosphere on the solar five-minute oscillations
Authors: Pamyatnykh A. A.
Published: June 2019

The influence of the modified treatment of subphotospheric convection, as recommended by Deupree (1979) and by Deupree and Varner (1980), on the frequencies of solar five-minute oscillations of degree 1 = 1–100 is studied. As compared with the results for a standard solar model, the convection theory modification has practically no effect on the frequencies near the low frequency edge of the observational interval (at ν ⋍ 2000 μHz), but causes a frequency decrease for high overtones; the effect is larger at larger frequencies. At ν ⋍ 4000 μHz the frequency decrease is about 4–6 μHz for all 1 ≤ 40 and about 8–10 μHz for 1 ⋍ 60–100. If, additionally, we use the dependence T(τ) according to Holweger and Müller (1974) instead of the HSRA model, the joint effect is 1.5–2 times larger. In this case the slope of the theoretical curves in “echelle diagrams” turns out to be in agreement with the observational one for 1 ≤ 20, but the frequencies themselves are approximately 10 μHz lower than those from observations.
Inversion of asymptotic gravity-mode frequencies and its application to the Sun
Authors: Ellis A. N.
Published: June 2019

Solar gravity modes can be used to probe the stratification below the convection zone. An asymptotic formula for high-order gravity-mode frequencies has been obtained in terms of a stratification parameter β. The domain of validity of this formula is investigated by least-squares regression of frequencies obtained from a theoretical model. Random noise is introduced to simulate real observations. An estimate is made of the critical noise-level above Which β cannot be inferred.
A search of the effects of magnetic field in the solar five-minute oscillations
Authors: Vorontsov S. V.
Published: June 2019

An overshoot region near the base of the solar convection zone may be the region where intense magnetic fields are stored during the solar cycle (Spiegel and Weiss, 1980; Schmitt and Rosner, 1983; Pidatella and Stix, 1986). In this report we study the possible influence of such a field on the frequencies of the solar five-minute oscillations.
Sunspot seismology
Authors: Thomas John H. , Lites Bruce W. , Abdelatif Toufik E.
Published: June 2019

The 5 minute oscillations in a sunspot umbra are the response of the sunspot to forcing by the 5 minute p-modes in the surrounding convection zone (Thomas 1981). This interaction of solar p-modes with a sunspot can be used to probe the structure of a sunspot beneath the visible surface of the Sun (Thomas, Cram, and Nye 1982). Here we report briefly the results of both an observational study and a simple theoretical analysis of this interaction. A full account of these results will be published elsewhere (Abdelatif, Lites, and Thomas 1986; Abdelatif and Thomas 1987).
The solar oscillations spectrum and the solar cycle
Authors: Jiménez A. , Pallé P.L. , Pérez J.C. , Régulo C. , Cortés T. Roca , Isaak G.R. , McLeod C.P. , van der Raay H.B.
Published: June 2019

During the summer seasons of the years 1977 to 1985 daily velocity measurements of solar global oscillations have been obtained using a resonant scattering spectrometer. After calculating the power spectra of the daily residuals, the mean for each season is found. Several discrete frequency intervals are defined in the spectrum which yield information on the characteristics of the oscillations and noise levels. The mean power in these intervals and the cut-off frequency of the p-mode spectrum, determined for each year, are correlated with the solar activity cycle. Furthermore, several series of 13 contiguous days for each year are analyzed. The frequency and amplitude of the p modes of 1 ≤ 3 and 11 ≤ n ≤ 33 are determined and their average for these years is found. The frequency differences between modes of the same degree 1 and between neighbouring modes are found. Their variation over the years is compared with the solar activity cycle.
Asteroseismology: results and prospects
Authors: Däppen W. , Dziembowski W.A. , Sienkiewicz R.
Published: June 2019

Asteroseismology is interpreted as an extension of the field of variable stars, and not just as the stellar analogue of helioseismology. The main effects of stellar mass and evolution on oscillation frequencies are discussed with the help of simplified wave-propagation diagrams. Frequency separations resulting from asymptotic expressions are compared with the corresponding results from numerical computations. The validity of asymptotic theory can be gauged in this way. The seismological issues of solar-like stars and Ap stars are discussed in some detail, and a progress report on the equation of state for stellar interiors is given. The review ends with a summary of properties and important physical problems for selected classes of variable stars.
Search for oscillations in some Ap stars
Authors: Belmonte J.A. , Pallé P.L. , Cortés T. Roca
Published: June 2019

Photometric observations of some Ap stars with a 50 cm telescope have been carried out at Izaña (Tenerife) in February 1986. The stars observed were, generally, magnetic - cool Ap stars. A search for global oscillations in the range 3 to 15 minutes has been undertaken and they seem to be present in some of the stars observed.
An improved limit for the rate of period change in the ZZ Ceti star G117-B15A or The Most Stable Optical Clock Known
Authors: Kepler S.O. , Winget D.E. , Robinson E.L. , Nather R.E.
Published: June 2019

The rate of change of period with time for the g-mode pulsations in ZZ Ceti stars depends directly on the cooling timescale for a DA white dwarf, and therefore a measurement of its value can yield an evolutionary timescale for the white dwarf. We have obtained an upper limit for the rate of change of the period of the dominant pulsation in the light curve of the ZZ Ceti star G117-B15A of |dP/dt| ≤ 9.9 × 10−15 s/s at the 68% confidence level, equivalent to a timescale for period change of
On the excitation of solar five-minute oscillations
Authors: Antia H.M. , Chitre S.M. , Gough D.O.
Published: June 2019

A simple prescription for the dynamics of convection perturbed by stellar pulsation is used in an estimation of the growth rates of solar five-minute modes. Convection appears to enhance the excitation of the modes, and the maximum in the growth rate versus frequency found previously when oscillatory convective perturbations were ignored is still present.
Gravity wave generation by large scale bubbles
Authors: Brandenburg Axel
Published: June 2019

The response of an isothermal atmosphere to small disturbances in entropy is studied taking compressible effects fully into account. The method of Green's functions is applied to solve the linearized hydrodynamic equations by Fourier transformation. A bubble may be created by perturbing the entropy within a finite volume. At first Lamb waves will be then emitted radially and the bubble undergoes a series of Brunt-Väisälä oscillations. We find that horizontally propagating waves are generated only by large bubbles “exceeding a radius of about ten pressure scale heights, whereas smaller bubbles lead to motions propagating principally in the vertical direction.
Overstable convection in a non-uniform magnetic field
Authors: Hermans D. , Goossens M. , Kerner W. , Lerbinger K.
Published: June 2019

The linear spectrum of a non-homogeneous, compressible and thermally conducting planar plasma with a vertical gravitational field and a sheared horizontal magnetic field is studied. It is shown that the spectrum has two continuous parts. The Alfvén continuum of linear ideal MHD is unaffected by radiative conduction, but the slow continuum is removed and replaced by a new continuous part which has been called isothermic continuum. Purely exponentially growing and overstable normal modes have been determined numerically and the distribution of their eigenfrequencies in the complex plane has been studied. The eigenfrequencies lie on specific curves in the complex plane which are partially determined by the isothermic continuum.
Continuous magnetic calibration of (velocity) sensitivity of oscillation spectrometers
Authors: Isaak G.R. , Jones A.R.
Published: June 2019

Modulation of the magnetic field in optical resonance spectrometers in order to calibrate the slope of the observable intensity ratios in terms of differential velocities is described.
Observational Parameters: Definitions and Limits
Authors: Lutz J.H.
Published: June 2019

This review paper gives an overview of many of the observational topics that will be covered during the symposium. Trends and new developments in planetary nebula observations will be highlighted.
Unified Model Atmosphere Studies of Central Stars of Planetary Nebulae
Authors: Gabler R. , Gabler A. , Méndez R. H. , Kudritzki R. P.
Published: June 2019

A first step in the accurate quantitative spectroscopic analysis of central stars of PN has been based on fitting the results of NLTE, hydrostatic, plane-parallel model atmosphere calculations to the observed H and He absorption-line profiles in high-resolution spectra of bright central stars (Méndez et al. 1988, A&A 190, 113 and subsequent papers). Such analyses have provided very useful determinations of the basic atmospheric parameters: Teff, log g and He abundance.
Spectral Analyses of WC-Type Central Stars
Authors: Hamann W.-R. , Koesterke L.
Published: June 2019

Models have been developed in Kiel for massive (Pop. I) WR stars which account for multi-level non-LTE radiation transfer in spherically expanding atmospheres. The published (Koesterke et al. 1992) grid of models for WC composition (40% helium, 60% carbon by mass) can be applied to low-mass stars as well by means of the scaling properties of WR spectra (Hamann et al. 1992) and allow a rough guess of the parameters, while individual calculations are necessary for a detailed analysis and the determination of the chemical composition.
Advances in Numerical Simulations of Gaseous Nebulae
Authors: Ferland Gary J.
Published: June 2019

I outline recent advances in numerical simulations of gaseous nebulae. These fall into three major areas; the Opacity Project and its extensions, the role of grains within the ionized gas, and the effects of mechanical heat on the nebula. These advances, together with improvements in stellar atmosphere calculations, should lead to a new generation of more realistic simulations of conditions in planetary nebulae and predictions of their emitted spectra.
Evolution of PN Morphologies: Concepts, Models and Observations
Authors: Balick Bruce
Published: June 2019

The shapes of planetary nebulae (PNs) provide paleontological clues about the origin and evolution of the gas expelled in the late phases of stellar evolution. The morphological classes of planetaries and various structural components of the nebulae are interpreted as hydrodynamic interactions of episodes of relatively brief, axisymmetric wind driven mass-loss events. Theoretical studies of the past five years are compared with extant data to show that astrophysical hydro models are achieving a very high level of success as explanations for the shapes of most PNs.

The most successful models are those for which the star is assumed to expel much or most of its mass in an equatorial wasteband. In stark contrast are dense ansae, dense and low-ionization knots of fast-moving gas, for which the mass distribution is decidedly polar. The origins of both the equatorial wastebands and polar knots remain decidedly enigmatic.
Trigonometric Parallaxes of Planetary Nebulae
Authors: Pier J. R. , Harris H. C. , Dahn C. C. , Monet D. G.
Published: June 2019

Parallaxes are presented for nine Planetary Nebulae central stars.
Reddening Distances for Planetary Nebulae from Broad Band BVIc CCD Imaging
Authors: Pollacco D.L. , Ramsay G.
Published: June 2019

If the zero age main sequence is expressed in the (V–I) versus (B–V)–(V–I) plane the reddening lines are found to lie at a great enough angle to allow reasonably accurate spectral type classification for stars later than ∼ F5. Earlier spectral types can also be identified but with lower accuracy. Comparison with the Q method of UBV photometry and with spectra of some of the program stars shows that the BVIc technique produces reliable results. As late–type stars constitute the most numerous spectral types and are plentiful in all galactic plane directions BVIc reddening distances can be derived close to the desired direction (although to smaller distances than techniques that utilize early type stars). The applicability of the technique is further enhanced by the use of CCDs which generally have a spectral response well suited for BVIc imaging observations. Using the new technique the distance to the PN NGC2440 was found to be (3100 ± 320)pc.
High-Resolution CCD Imagery of NGC 6537 and NGC 7027
Authors: Heap S.R.
Published: June 2019

Using Hα and Hβ images obtained at the CFHT, we derived the spatially varying reddening within NGC 6537 and NGC 7027. We then corrected the observed Hβ picture for dust extinction to obtain pictures more in accord with radio maps. The left panels below show NGC 6537; the right panels, NGC 7027. The top panels show the observed Hβ picture, and the bottom panels, the Hβ picture corrected for spatially varying extinction. Note that the bright optical knot in NGC 7027 corresponds to a hole in the extinction.
Optical Spectroscopy of Six Carbon-Rich Proto-Planetary Nebulae
Authors: Hrivnak B.J.
Published: June 2019

We are engaged in a program of optical spectroscopy of proto–planetary nebulae (PPN). The objects were initially selected from the IRAS database on the basis of their strong infrared excesses, indicating dust temperature of 150–250 K. Spectra have been obtrained at medium resolution for the purpose of obtaining the spectral type, luminosity class, and to search for chemical peculiarities resulting from the post–AGB nature of the objects. We found our PPN candidates to typically display F–G supergiant spectra.
Twodimensional Axialsymmetrical Hydrodynamical Simulations of PN-Evolution
Authors: Zweigle J. , Bremer M. , Grewing M.
Published: June 2019

In order to investigate the early evolution of planetary nebulae (PNe) we solved numerically the hydrodynamical equations in cylindrical coordinates (r, z) assuming azimutal symmetry. The numerical method used is described in detail by Mair et al. (1988). Our simulations model the interaction of a fast, tenuous, spherical symmetrical central star wind with a slow, dense, aspherical Red Giant Envelope (RGE) expelled from the progenitor star. For the aspherical RGE with a polar/equatorial density contrast we used the initial model given by Mellema et al. (1991) in cylindrical coordinates. We have investigated the influence of each initial model parameter upon the evolution of PNe. Thereby we confirm that the polar/equatorial density contrast in the RGE and the thickness of the RGE-disk play an important role for the morphology of PNe. In agreement with the results from Mellema et al. (1991). The polar/equatorial density contrast in the RGE influences the ratio of the distances of the bright inner rim to the central star in z- and r-direction. This ratio increases with decreasing polar/equatorial density contrast. We find the thickness of the RGE-disk to be a key parameter for getting an elliptical or a butterfly PN: thin RGE-disks produce the first type of nebulae, thick disks the latter. We thank G. Mair, E. Müller and W. Hillebrandt for making available to us a copy of the SADIE code.
The Evolution of Planetary Nebulae, Their Precursors and Their Progeny — A Commentary
Authors: Iben Icko
Published: June 2019

There appears to exist in the minds of most of the participants of this conference a highly stylized picture of how the majority of all stars evolve after reaching the asymptotic giant branch. This is a fascinating development as, just three decades ago, no one understood what an asymptotic giant branch (AGB) star is or does, either theoretically or observationally, and, just two decades ago, no one understood the nature of the transition from AGB to planetary nebula, other than that it happened. And, yet, today, the evolution from AGB to planetary nebula and to white dwarf is described by a very beguiling picture whose outlines have become substantially fixed.
Brown Dwarf Companions to Solar-Type Stars and other Brown Dwarfs
Authors: Martín Eduardo L. , Connelley Mike , Potter Dan , Bouy Hervé
Published: June 2019

We report on our ongoing imaging efforts to detect brown dwarfs orbiting solar-type stars and other brown dwarfs. We study the properties of brown dwarf companions as a function of primary mass. Our results indicate that the frequency of brown dwarf companions around solar-type stars for separations larger than about 40 AU is non-negligible. The frequency of brown dwarf binaries is about 20%. There is a dearth of brown dwarf binaries with separations larger than ∼20 AU. We propose that brown dwarf systems are a scaled down version of stellar systems, which probably form via triggered collapse of small molecular cores.
Total Organic Carbon in Red Paleosoils and Basalts from ODP Leg 197 and their Potential use as Suitable Models for Mars Soil Analogues
Authors: Bonaccorsi Rosalba
Published: June 2019

Although on Mars no near-surface life has been detected, some preservation of organics with depth is expected. Stratigraphic and geochemical information on low-organic carbon (50% samples with Total Organic Carbon = 0.05 − 0.12%) Fe-oxides/oxyhydroxide-rich horizons of deeply buried red paleosoils (late Paleocene-early Eocene(?) in age) are presented here. They were retrieved during the Ocean Drilling Program (ODP) Leg 197 (Emperor Seamounts, North Pacific Transect). Organic traces in Hole 1205A are likely to reflect a complex history of paleosoil formation. Materials from an extremely deep (sub-basement) diagenetic setting, i.e., 46.8 to 309.9 meters below seafloor (mbsf), could represent a model for possible deep subsurface soils preserved on Mars.
Precambrian Surface Temperatures and Molecular Phylogeny
Authors: Schwartzman David , Lineweaver Charles H.
Published: June 2019

The timing of emergence of major organismal groups is consistent with the climatic temperature being equal to their upper temperature limit of growth (Tmax), implying a temperature constraint on the evolution of each group, with the climatic temperature inferred from the oxygen isotope record of marine cherts. Support for this constraint comes from the correlation of Tmax with the rRNA molecular phylogenetic distance from the last common ancestor (LCA) for both thermophilic Archaea and Bacteria. In particular, this correlation for hyperthermophilic Archaea suggests a climatic temperature of about 120°C at the time of the LCA, likely in the Hadean.
Against the Use of Power Law Luminosity Functions for ET Beacons
Authors: Dreher John W.
Published: June 2019

Not infrequently it is suggested that the luminosity function (the distribution of the space densities of objects as a function of their luminosities) of extraterrestrial transmitters can plausibly be modeled as a power law, L-α, of the luminosity L (Drake 1973; Gulkis 1985; Lampton 2002). This assertion is usually motivated by analogy to the luminosity function for stars in the solar vicinity, which can be (very) roughly modeled as such a power law Fig. 1, data from Mihalas and Binney (1981). The argument then continues that if the power law is sufficiently flat (α < 1.5), then a flux limited sample of transmitters will be dominated by the most luminous, since their relative scarcity is more than made up by the much larger volume in which they can be detected. This is an extreme example of the infamous Malmquist bias (Mihalas & Binney 1981). It is then concluded that if the distribution of ET transmitters were to have such a flat distribution, then the seemingly obvious SETI search strategy of starting with the nearest stars and working outward would be incorrect, and, since we do not know the value of α it makes sense to “hedge” our bets by performing all-sky SETI searches even if such searches are much less sensitive.
Searching for Extraterrestrial Technologies Within Our Solar System
Authors: Tough Allen , Lemarchand Guillermo A.
Published: June 2019

We speculate about possible cosmic exploration by extraterrestrial civilizations using interstellar smart probes. We call attention to some emerging technologies that may be used for interstellar exploration. We estimate that advanced civilizations may already have these technologies and may be using them to contact their galactic neighbors. We explore some observational consequences of these contacting strategies.
Wide Cultural Communications in Interstellar Messages
Authors: Musso Paulo.
Published: June 2019

The idea of communicating cultural concepts in a SETI message, suggesting that analogy may be a useful tool, is developed in this paper in a systematic way, aiming at the construction of an effective message with wide cultural content. Here, I discuss both materials and methods in relation to three questions. Firstly, which of the main concepts of our culture are likely to be communicated in this way? Secondly, is the conceptual cluster (Dutil, 2004) sufficient as a basis to apply the analogical methodology or should it be extended further? And lastly, what is the possible contribution of the different kinds of logic (i.e. classical, mathematical, fuzzy and so on) and which are their relationships (if any) with analogy?
Simulations of Large Scale Structure Formation: The Connection to Smaller Scales
Authors: Steinmetz Matthias
Published: June 2019

Maps of the cosmos, in particular maps of the cosmic microwave background and of the large scale distribution of galaxies have been crucial ingredients in the development of the standard model of structure formation, sometimes also labeled “concordance model”. This model has proven to be remarkably successful in explaining an impressive array of observations on scales of hundreds of kpc to thousands of Mpc. In this contribution I will attempt to extend those studies to smaller, (sub)galactic scales and will confront detailed gas-dynamical simulations of the formation of individual galaxies with observational data on these scales, reporting some successes and failures of this endeavor. Ongoing surveys that are mapping the distribution of stars in the Milky Way should be able to clearly identify the imprints of the hierarchical galaxy formation process providing an independent check of the validity of the structure formation paradigm.
The Digitized First Byurakan Survey - DFBS
Authors: Mickaelian A. M. , Sargsyan L. A. , Erastova L. K. , Balayan S. K. , Gigoyan K. S. , Hovhannisyan L. R. , Nesci R. , Gaudenzi S. , Massaro E. , Rossi C. , Sclavi S. , Trevese D. , Weedman D. , Houck J. , Barry D. , Brandl B.
Published: June 2019

The First Byurakan Survey (FBS) is the largest spectral survey in the Northern sky. One can select objects by color, broad absorption and emission lines, and SED; classify and investigate them. The digitization of the FBS is aimed at making a DFBS database available for the astronomical community. Besides scanning, we are creating plate solutions, extraction software, wavelength and flux calibration, templates for different types of objects, numerical classification, a catalog of objects, a database of spectra, a user interface and a DFBS web page. New research projects based on the DFBS are possible, including a search for new QSOs and other AGN, a continuation of the second part of FBS, and identifications of radio, IR and X-ray sources. The DFBS database will be available at the end of 2004.
Mapping the Reionization Era Through the 21 cm Line Emission
Authors: Ciardi Benedetta , White Simon D. M.
Published: June 2019

We will present simulations of the IGM reionization process and discuss its observability through the 21 cm line. We find that the primordial stellar sources considered in this study give a value of the reionization epoch and of the electron optical depth consistent with the observations by WMAP, without invoking the presence of additional sources of ionization. Depending on the redshift of reionization, broad-beam observations at frequencies < 100–150 MHz with the next generation of radio telescopes should reveal angular fluctuations in the sky brightness temperature in the range 5 —20 mK on scales < 5 arcmin.
SWIRE and SIRTF Surveys
Authors: Lonsdale Carol J.
Published: June 2019

The launch of SIRTF on August 25, 2003 opens an exciting new era for the infrared. Building on the legacy of IRAS, COBE & ISO, SIRTF will image the sky from 3.6–160 μm in tiered surveys, from wide (∼80 sq. deg.) reaching z∼1 in depth for L*FIR galaxies, to small, deep, confusion-limited surveys. SIRTF will measure the accumulation of stellar mass at high redshift, and the evolution of dusty systems (disks, starbursts & AGN) since z∼4, on size scales up to several hundred Mpc. The next decade will also see two major all-sky IR surveys, ASTRO-F and WISE (Wide-field Infrared Survey Explorer), and the launch of Herschel and Planck.
X-ray Cluster Large Scale Structure and Cosmology
Authors: Pierre Marguerite
Published: June 2019

We outline the main arguments in favor of cosmological X-ray surveys of galaxy clusters. We summarize recent advances in our understanding of cluster physics. After a short review of past surveys, we present the scientific motivations of the XMM Large Scale Structure survey. We further illustrate how such a survey can help constrain the nature of the dark energy as well as cluster scaling law evolution, i.e. non-gravitational physics.
Probing the Redshift Desert Using the Gemini Deep Deep Survey: Observing Galaxy Mass Assembly at z > 1
Authors: Glazebrook Karl ,   Gemini Deep Deep Survey Team
Published: June 2019

The aim of the Gemini Deep Deep Survey is to push spectroscopic studies of complete galaxy samples (both red and blue objects) significantly beyond z = 1; this is the redshift where the current Hubble sequence of ellipticals and spirals is already extant. In the Universe at z = 2 the only currently spectroscopically confirmed galaxies are blue, star-forming and of fragmented morphology. Exploring this transition means filling the ‘redshift desert’ 1 < z < 2 where there is a dearth of spectroscopic measurements. To do this we need to secure redshifts of the oldest, reddest galaxies (candidate ellipticals) beyond z > 1 which has led us to carry out the longest exposure redshift survey ever done: 100 ksec spectroscopic MOS exposures with GMOS on Gemini North. We have developed an implementation of the CCD “nod & shuffle” technique to ensure precise sky-subtraction in these ultra-deep exposures. At the halfway mark the GDDS now has ∼ 36 galaxies in the redshift desert 1.2 < z < 2 extending up to z = 1.97 and I < 24.5 with secure redshifts based on weak rest-frame UV absorption features complete for both red, old objects and young, blue objects. The peak epoch of galaxy assembly is now being probed by direct spectroscopic investigation for the first time. on behalf of the GDDS team I present our first results on the properties of galaxies in the ‘redshift desert’.
Turbulence and magnetic fields in molecular clouds
Authors: Henriksen R. N.
Published: June 2019

in this paper I first review some of the simple structural concepts associated with compressible turbulence. In particular the hierarchical or self-similar fractal structure to be expected is formulated in a manner readily compared to the observations, and to previous work. In the next section I present the first results of a wavelet analysis on molecular clouds, which seem to comfirm the hierarchical scaling. I conclude with an extention of the theory to include magnetic fields. This latter theory represents an alternative to the more conventional dynamo theory.
Clouds, cores, and stars in the nearest molecular complexes
Authors: Myers P. C.
Published: June 2019

The properties and structure of six molecular complexes within 500 pc of the Sun are described and compared. They are generally organized into elongated filaments which appear connected to less elongated, more massive clouds. Their prominent star clusters tend to be located in the massive clouds rather than in the filaments. The complexes have similar structure, but big differences in scale, from a few pc to some 30 pc. They show a pattern of regional virial equilibrium, where the massive, centrally located clouds are close to virial equilibrium, while the less massive filaments and other small clouds have too little mass to bind their observed internal motions. Complexes can be ranked according to increasing size, mass, core mass, and the mass and number of the associated stars: they range from Lupus to Taurus to Ophiuchus to Perseus to Orion B to Orion A. The cores in nearby complexes tend to have maps which are elongated, rather than round. The core size, velocity dispersion, and column density of most cores are consistent with virial equilibrium. Cores in Orion tend to exceed cores in Taurus in their line width, size, temperature, mass, and in the mass of the associated star, if any. Stars in Orion tend to be more numerous and more massive than in Taurus, while those in Taurus tend to be more numerous and more massive than in Lupus. The mass of a core tends to increase with the mass of the cloud where it is found, with the mass of the star cluster with which it is associated, and with its proximity to a star cluster. These properties suggest that complexes and their constituent cores and clusters develop together over time, perhaps according to the depth of the gravitational well of the complex.
Dust emission from star forming clouds: a progress report
Authors: Mezger P. G. , Sievers A. , Zylka R.
Published: June 2019

Model computations of protostellar evolution depend very strongly on the initial conditions: Fragmentation of massive cloud cores or coagulation of substellar condensations, the physical state of gas and dust (e.g. the formation of ice-mantles and grain coagulation), the presence of magnetic fields and its effect on gas and dust, and the formation of accretion disks as a consequence of an initial angular momentum of the protostellar condensation. The MPIfR bolometer group together with the molecular spectroscopists R. Mauersberger and T.L. Wilson have embarked on a program aimed at the exploration of the earliest evolutionary stages of high- and low-mass star formation. Here follows a brief progress report.
Some processes influencing the stellar initial mass function
Authors: Larson Richard B.
Published: June 2019

Current evidence suggests that the stellar initial mass function has the same basic form everywhere, and that its fundamental features are (1) the existence of a characteristic stellar mass of order one solar mass, and (2) the existence of an apparently universal power-law form for the mass spectrum of the more massive stars. The characteristic stellar mass may be determined in part by the typical mass scale for the fragmentation of star forming clouds, which is predicted to be of the order of one solar mass. The power-law extension of the mass spectrum toward higher masses may result from the continuing accretional growth of some stars to much larger masses; the fact that the most massive stars appear to form preferentially in cluster cores suggests that such continuing accretion may be particularly important at the centers of clusters. Numerical simulations suggest that forming systems of stars may tend to develop a hierarchical structure, possibly self-similar in nature. If most stars form in such hierarchically structured systems, and if the mass of the most massive star that forms in each subcluster increases as a power of the mass of the subcluster, then a mass spectrum of power-law form is predicted. Some possible physical effects that could lead to such a relation are briefly discussed, and some observational tests of the ideas discussed here are proposed.
Luminosity function, star density, and star formation efficiency in regions of star formation - near infrared observations -
Authors: Hodapp Klaus-Werner , Rayner John , Chen Hua
Published: June 2019

Clusters of young stars have been found near a number of compact HII regions. These clusters do not show a turnover in the K-band luminosity and are probably several million years old. In L 1641 only moderate clustering tendency has been observed and many sources show signs of extremely young age.
Fragmentation in molecular clouds
Authors: Clark Frank O. , Prusti Timo , Laureijs R. J.
Published: June 2019

B209. Fragments are detected in the outer parts of the B209 molecular cloud in a region of density 1000 cm−3 using 12CO, 13CO, H2CO, IRAS 60 and 100 μm images, discernable as velocity components, and have characteristics: ∼ 0.4 pc; ∼ 2 M⊙; ∼ 1.6 M⊙ km/s pc; Tgas ∼ 11 K; Tdust> ∼ 16 K??. The system of fragments has ∼ 0.5 pc and ∼ 1.6 M⊙ km/s pc. These are illustrated in Figure 1, which contains an IRAS 100 μm map made with Geisha and attendant U. Köln Gornergrat CO spectra for each respective fragment. The differing characteristic velocities of each fragment are readily apparent.
“The mass distribution of the young stellar population in Chamaeleon I and in Rho Ophiuchi”
Authors: Gregório Hetem Jane C. , Lépine J.R.D. , Ortiz R.
Published: June 2019

We obtain the mass distribution and the age distribution of the young stars associated with Chamaeleon I and Rho Ophiuchi, two nearby sites of star formation. Our method consists in determining the temperature and the luminosity of each object in order to locate it on the HR diagram, and then comparing the position on the HR diagram with the evolutionary tracks and isochrones presented by Cohen and Kuhi (1979). The star-formation process is found to have started more recently in ρ Oph than in Cham I.
Observational constraints on angular momentum transfer during gravitational collapse*
Authors: Keto Eric
Published: June 2019

A simple calculation of the expected spectral signatures of model protostellar accretion flows suggests how the rotation curve of the accretion disk may be deduced from radio frequency molecular line observations. We compare synthetic observations with actual data to derive rotation curves, braking torques, and minimum magnetic field energies required to effect the braking.
New Sample of Young Stellar Objects
Authors: Moy S. M. , MacDonald G. H. , Habing R. J.
Published: June 2019

in recent years there has been much interest in the study of large samples of molecular cloud cores and related infrared sources in an attempt to observe true protostars - objects in transition between a molecular cloud core and a young stellar object (YSO). We present here a survey of 48 possible protostellar objects chosen initially by their IRAS colours and subsequently observed in (1—0) HCO+ emission at Onsala in Feb 1990. Future observations in (3—2)13CO & (3—2)12CO will be made with the JCMT and in (1,1) and (2,2) NH3 emission with the Bonn 100m telescope.
Turbulence in TMC1-C and ρ-Oph core
Authors: Sunada K. , Kitamura Y. , Hasegawa T. , Hayashi M.
Published: June 2019

We made 13CO and C180 (both J = 1 — 0) maps of the 4′ × 4′ (0.2 pc × 0.2 pc) area toward TMC1-C and ρ-Oph core with the 45-m telescope of the Nobeyama radio Observatory in order to find small scale velocity fluctuation in molecular clouds based on the analysis described by Kleiner and Dickman (1987).
Characterisation of spatial structure in molecular clouds
Authors: Veeraraghavan Shoba , Fuller Gary A.
Published: June 2019

Two topological tools for studying the global structure of molecular clouds, the genus and the contour-crossing statistic, are discussed. Preliminary results for the Taurus molecular cloud complex are presented.
Status of Experiments for Direct Detection of Galactic Dark Matter Particles
Authors: Smith Peter F.
Published: June 2019

There is increasing evidence that the majority of dark matter is non-baryonic. Principal candidates are weakly interacting massive particles (WIMPS), axions, and neutrinos. There has been increasing effort on sensitive WIMP searches, motivated in particular by supersymmetry theory, which predicts a stable neutral particle in the mass range 10-1000 GeV. Interactions of these with normal matter would produce low energy nuclear recoils which could be observed by underground detectors capable of discriminating these from background. Current experimental progress is summarised, together with plans for more sensitive experiments. These include gaseous detectors with directional sensitivity, offering the prospect of a ‘dark matter telescope’ which would provide information on the dark matter velocity distribution. Axions could be detected by conversion to microwave photons, and experimental sensitivity is approaching the theoretically-required levels. Relic neutrinos could also form a component of the dark matter if any has a cosmologically significant mass, and the latter could be checked with a new detector able to detect the higher neutrino flavours from a Galactic supernova burst. More distant future possibilities are outlined for direct detection of relic neutrinos by coherent scattering.
Constraining the Cosmic Mass Density from the SBF Survey Peculiar Velocities
Authors: Blakeslee J. P. , Tonry J. L. , Dressler A. , Ajhar E. A. , Davis M. , Willick J. A. , Strauss M. A. , Narayan V. K.
Published: June 2019

The recently completed I-band SBF Survey of Galaxy Distances contains about 300 galaxy distances within cz ≲ 4000 km/s. These data allow for good constraints on the local mass density and velocity fields. The mass density parameter βI ≡ Ω0.6/bI, where bI is the biasing factor of the IRAS redshift survey galaxies, is found to be βI ≍ 0.45.
Bayesian Joint Estimation of Non-Gaussianity and the Power Spectrum
Authors: Rocha Graça , Magueijo João , Hobson Mike , Lasenby Anthony
Published: June 2019

This paper gives a summary of our rigorous, non-perturbative, Bayesian framework which enables one jointly to test Gaussianity and estimate the power spectrum of CMB anisotropies. A detailed and thorough presentation of this new technique has been given in Rocha et al. 2000. There we apply our method to Very Small Array (VSA) simulations based on signal Gaussianity, showing that out algorithm is indeed not biased.
Proper motions of water masers: W 51 North, Main, and South
Authors: Imai Hiroshi , Sasao Tetsuo , Kameya Osamu , Watanabe Teruhiko , Omodaka Toshihiro , Nishio Masanori , Asaki Yoshiharu , Nakajima Jun-Ichi
Published: June 2019

We describe the proper motion measurements of water masers in the massive-star forming region W 51A and the analysis of the 3-D kinematics in three maser clusters of W 51A. We found a systematic expanding motion in one of the clusters named W 51 North, while no systematic motion was detected in other two clusters named W 51 Main and South. The 3-D motions of the clusters relative to the position reference feature in W 51 North indicate a separating motion between the W 51 North and the W 51 Main/South clusters. We estimated the distance to W 51 North as to be 6.7±2.1 kpc on basis of the statistical parallax and the model fitting methods.