bluuebunny/crossref_metadata_2025_split huggingface dataset:
Doppler Imaging of Stars with Surface Inhomogeneities
Authors: Cameron Andrew Collier 
Published: July 2016

AbstractI review recent progress in the field of stellar surface imaging, with particular reference to advanced methods for mapping surface-brightness distributions on magnetically active late-type stars. New signal enhancement techniques, utilising profile information from hundreds or thousands of photospheric lines simultaneously, allow images to be derived for stars several magnitudes fainter than was previously possible. For brighter stars, the same techniques make it possible to map features as small as two or three degrees in extent on the stellar surface. While this opens up whole new areas of research, such as the ability to use starspot tracking to study surface differential rotation patterns on single and binary stars, caution must be exercised in the treatment of “nuisance” parameters such as the stellar rotation rate, surface abundances and radial velocity. At the very high S:N levels we now use, the effects of systematic errors in these parameters are easier to identify, isolate and eliminate. This leads to the possibility of making precise radial velocity variations (at the few hundred m s−2 level or better) in late-type stars even with equatorial rotation speeds as high as 100 km s−1. This is particularly topical given the recent discovery that one of our prime imaging targets, the young southern K0 dwarf AB Doradus, has an astrometric companion in a highly eccentric orbit with an inferred mass close to the H-burning limit.
Discovering new spectroscopic components in visual multiple stars
Authors: Tokovinin A.A. 
Published: July 2016

AbstractA radial velocity survey of the components of visual multiple stars has been done since 1994 with the correlation radial velocity spectrometer. About 50 spectroscopic sub-systems have been discovered, and a summary of the 30 published orbits is given. Difficulties of measuring the radial velocities of multiple stars are discussed and illustrated by 2 examples. New discoveries will lead to a better understanding of the formation of multiple stellar systems. Close and wide sub-systems can not be considered as a result of independent random combination, but are related by common origin. Almost all close binaries with periods less than 6 days possibly have more distant components which assisted in the formation of close pairs by taking away their angular momentum. On the other hand, among the distant visual tertiary companions the frequency of sub-systems with periods under 100 days is about 3 times higher than for field G dwarfs.
Inner Spiral Arms of the Barred Galaxy NGC 4314
Authors: Ann H. B. , Kwon K. H. 
Published: July 2016

AbstractThe nuclear region of the barred galaxy NGC 4314 was observed and modeled by VIJHK photometry, long-slit spectroscopy, and SPH simulations. Young stellar populations is supposed to be made from the gas which are accumulated in the nuclear ring and/or inner spiral arms by the strong bar potential.
Neutral Gas in Resonance-Ring Galaxies
Authors: Ryder Stuart , Buta Ronald , Toledo Hector 
Published: July 2016

AbstractWe have mapped the distribution and kinematics of H ɪ in NGC 1433 and NGC 6300 with the Australia Telescope Compact Array, in order to test the association between resonances and ring phenomena. We find a bar pattern speed in NGC 1433 of Ωp = 26 ± 5 km s kpc−1, and postulate that NGC 6300 is still evolving to a mature resonance-ring galaxy.
Buckling Bars and Boxy Bulges
Authors: Merrifield M. R. 
Published: July 2016

AbstractIt has been suggested that the peanut-shaped bulges seen in some edge-on disk galaxies are produced when bars in these galaxies buckle. This paper reviews the modelling which seeks to show how bars buckle, and I present a very simple new model which captures the essential physics of this process. I then discuss the problems in establishing observationally the connection between peanut-shaped bulges and bars. Confirmation of the link has proved difficult because boxy bulges are only apparent in edge-on galaxies whereas bars are only easily detectable in more face-on systems. Finally, I present a new technique which avoids this difficulty by searching for the distinctive kinematic signature of an edgeon bar; application of this method to spectra of peanut-shaped bulges reveals that they are, indeed, associated with hidden bars.
Gas and Stellar Kinematics in the Disk and Bar of Mrk 573
Authors: Afanasiev V. L. , Burenkov A. N. , Shapovalova A. I. , Vlasyuk V. V. 
Published: July 2016

AbstractResults of 3D-spectroscopy for the nearby Seyfert galaxy Mrk 573 obtained at the 6-m telescope with the scanning Fabry-Perot interferometer and the Multi-Pupil Field Spectrograph (MPFS) are presented. Emission lines images of the galaxy center demonstrate a complex structure of ENLR, coinciding with the radio data. An analysis of the velocity field shows that some gas structures do not lie in the plane of the galaxy. An explanation of the observed velocity field and gas distribution by radiation of a helical structure located inside an ionization cone is proposed.
Barred Extreme IRAS Galaxies
Authors: van Driel Wim , van den Broek Bert 
Published: July 2016

AbstractWe studied a statistically complete sample of 57 southern socalled extreme IRAS galaxies, i.e., objects with a high far-infrared/blue luminosity ratio, LFIR/LB>3, using optical (imaging and spectra), radio continuum, and CO(1–0) line observations. The sample can be divided into three distinct categories: dwarfs (20%), barred spirals (35%), and interacting systems (35%). The barred galaxies are generally morphologically undisturbed, isolated systems, with average star formation rates (4 M⊙ yr–1) and efficiencies (LFIR/MH2 = 16 L⊙/M⊙) for galaxies in our sample. An enhanced massive star formation rate is the cause of the infrared brightness in 93% of all galaxies in the sample. The nuclear region is the most important star formation locus, generally unresolved at 1" resolution, i.e., less than 0.2-0.6 kpc size (H0=75 km s–1 Mpc–1), though 2 kpc size in three cases. In about two-thirds of the extreme IRAS SB’s, fainter, diffuse (2.5-10 kpc size) massive star formation is seen in the bar as well.
Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 1365
Authors: Lindblad P. A. B. , Lindblad P. O. , Athanassoula E. 
Published: July 2016

Several authors have explored the field of gas dynamics in barred systems. One of the aims of these investigations was to compare the model gaseous response, due to some assumed underlying stellar gravitational field, with observed gas density distribution and kinematics of barred galaxies. The gas is known to respond in a highly non-linear way, and therefore should give clues to dynamical parameters like the mass distribution, positions and existence of principal resonances and thereby the pattern speed.High resolution HI data now exist for NGC 1365 (Jörsäter & van Moorsel 1995), and the kinematical HI data have been combined with optical long slit measurements to obtain the velocity field (Lindblad et al. 1995) used for extracting the rotation curve, representing the axisymmetric forces in NGC 1365, and for comparisons with models. A mosaic image of NGC 1365 in the J-band was used to compute the perturbing potential used in the models.
A New Fueling Process in a Weak Bar
Authors: Wada Keiichi , Habe Asao 
Published: July 2016

AbstractA massive gaseous disk in the central region of a galaxy sensitively responds to a weakly distorted potential, and a large amount of gas can be fed into within 1/20 of the core radius of the potential in several 107 yr. The ILRs, the dissipative nature of the gas, and the self-gravity of the gas are essential for triggering this effective fueling. We also found that a counterrotating gaseous core can be formed as a result of the fueling. Our result suggests that the merger of galaxies is not the only way to form the observed counterrotating core in galaxies.
Galactic Slow Bar as an Unstable Mode of a Stellar Disk
Authors: Polyachenko Evgenij V. , Polyachenko Valerij L. 
Published: July 2016

AbstractAn estimate for the slow bar instability boundary for a generalized disk polytropic model is derived. The effects of a spherical halo are studied: it turns out that a halo can be favorable to this instability (at the same time suppressing the bending instability).
Some Problems Related to Geodetic Datum Definitions for Terrestrial Measurements
Authors: Groten E. 
Published: July 2016

AbstractProblems related to the precj se definition of reference systems for measurements of crustal motion are discussed. Difficulties in defining vertical positions are emphasized. Using the Goddard Earth Model 6 and surface gravity data, a new absolute orientation vector for the European Datum is evaluated and corresponding deficiencies are discussed.
1.1.4 Pioneer 10 Observations of Zodiacal Light Brightness near the Ecliptic: Changes with Heliocentric Distance
Authors: Hanner M. S. , Sparrow J. G. , Weinberg J. L. , Beeson D. E. 
Published: July 2016

AbstractSky maps made by the Pioneer 10 Imaging Photopolarimeter (IPP) at sun-spacecraft distances from 1 to 3 AU have been analyzed to derive the brightness of the zodiacal light near the ecliptic at elongations greater than 90 degrees. The change in zodiacal light brightness with heliocentric distance is compared with models of the spatial distribution of the dust. Use of background starlight brightnesses derived from IPP measurements beyond the asteroid belt, where the zodiacal light is not detected, and, especially, use of a corrected calibration lead to considerably lower values for zodiacal light than those reported by us previously.
2.1.7 Dust in the Outer Solar System – Review of Early Results from Pioneers 10 and 11
Authors: Soberman R. K. , Alvarez J. M. , Weinberg J. L. 
Published: July 2016

AbstractThe Pioneer 10/11 spacecraft, launched in 1972 and 1973, carried three experiments to measure cosmic dust. A comparison of these first direct measurements of dust in the outer solar system indicates that the sizes, optical properties, and spatial distribution are more complex than previously supposed.
3.5 The Dust Coma of Comets
Authors: Michel K.W. , Nishimura T. 
Published: July 2016

AbstractAnalytical expressions for the dust entrainment in the limits of low and high gas production from cometary nuclei are derived. The resulting volume density is used to evaluate the dust production of Comets Encke and Kohoutek from IR-measurements. It is predicted, that the dust in solar direction was diffuse for Comet Kohoutek during approach to the Sun, but sharp for Comet Encke and nearly independent of heliocentric distance. The dust production rate of Encke ist not sufficient to sustain the Zodiacal cloud of micron sized particles. Particle impact probabilities and hazards are estimated for a space probe in a fly-by mission to Encke.
The Discovery and Observation of Multiple Stellar Systems
Authors: Batten A. H. , Scarfe C. D. 
Published: July 2016

AbstractThe difficulties of discovering and observing multiple stellar systems are reviewed and discussed with especial reference to those systems which are best observed by a combination of visual and spectroscopic or visual and photometric means. Attention is drawn to the difficulties that often exist in reconciling the results of two different methods of observation. A brief discussion of the possibility of detecting spectroscopically invisible companions of low mass is included in the paper.
A New Michelson Stellar Interferometer
Authors: Twiss R. Q. , Tango W. J. 
Published: July 2016

AbstractA new 1.87 m fixed-baseline interferometer designed for binary star observation is now in operation at the Italian outstation of the Royal Observatory Edinburgh. It has a theoretical resolving power of 0.015 arcsee and a limiting B magnitude of 6.5. Atmospheric seeing is dynamically corrected, allowing a quantitative measurement of fringe visibility.
White Dwarf Formation in Two-Body Systems: Sirius AB, Procyon AB, 40 Eri BC AND Stein 2051 AB
Authors: Roark Terry P. 
Published: July 2016

AbstractThe orbital histories of the systems Sirius AB, Procyon AB, 40 Eri BC and Stein 2051 AB are examined. It is assumed that the changes in the orbital elements are a direct result of mass loss from the white dwarf precursor component. This loss is considered to be isotropic and no exchange between the components is allowed. These histories, coupled with observed atmospheric abundances, theoretical ages and cooling times lead to the conclusion that stars as massive as 10M⊙ can be white dwarf progenitors. Indeed, in the case of Sirius B, there is evidence that the progenitor mass was not less than 8M⊙ and that the star did not lose mass in an explosive manner.
Review of the Dynamical Aspects of Triple Systems
Authors: Szebehely V. 
Published: July 2016

AbstractA classification of possible motions of triple systems is presented emphasizing the transient phenomena occurring in addition to the final (asymptotic) outcome and clarifying the discrepancies between the astronomical and mathematical formulations. A conjectured possible instability is described and it is shown that systems with negative total energy and low angular momentum may lead to instability and to the formation of binaries. The ejected or escaping star may have high velocity if the triple close approach preceding the escape is sufficiently close. The computational results of several systematic series of such escapes are applied to various stellar configurations.The present status of the fundamental problem of partitioning the phase-space into stable and unstable regions is reviewed and a recently developed technique, applicable to stellar dynamics is described. Recently discovered families of periodic orbits and previously established classical configurations are shown to weaken the general instability conjecture.The possible existence of triple systems in states of dissolution offer intriguing observational challenges regarding the discovery of these projected temporary trapezium type systems.
Numerical Experiments on the Decay of Three-Body Systems
Authors: Valtonen M. J. , Aarseth S. J. 
Published: July 2016

AbstractNumerical results are presented for calculations of stellar three-body systems. Among the triple systems with similar initial separations between each of the stars, the equal-mass systems are most stable with typical half-lives of about 40 crossing times. In the other extreme, systems with a very small total angular momentum or a large mass difference have half-lives of only about 10 crossing times. The escaping star is usually the lightest one, while the escape probability for the heaviest star approaches zero when its mass exceeds the combined mass of the other two stars by more than a factor of about 5. The final binary becomes very eccentric (ē ≳ 0.8) when the three stars are restricted to a plane and do not have a very high total angular momentum, or when the total angular momentum is very small.
Data Processing and Analysis for Space-Based Astronomy
Authors: Mistrik I. 
Published: July 2016

AbstractThe sensors on a spacecraft, the spacecraft data handling system, the mission support ground data system, the experimenter’s scientific data reduction and analysis system, the post-mission data storage and dissemination system all comprise elements of the data handling system for a space-based astronomy.Primary treatement is given to the experimenter’s scientific data system where the following aspects of astronomy missions are discussed: increasingly close operational contact of the experimenters with the sensors calls for moving data processing operations to the earliest possible point of the system. On the other hand, potential need for subsequent reprocessing of data would favor the central ground-based facility for initial processing with the open-end system philosophy.One approach, extant and planned implementation of the scientific data analysis system for the zodiacal light experiment of the solar probe Helios, is presented in detail, taking into consideration experience from the various astronomy missions, in particular Pioneer and Skylab.
The Use of Standardized Data Formats with the Westerbork Radio Telescope
Authors: Harten R.H. , Spoelstra T.A.Th. 
Published: July 2016

AbstractSince 1970 the Westerbork Synthesis Radio Telescope has been collecting data on galactic and extragalactic fields. The data is stored and cataloged on magnetic tape using a standard format. This data is routinely reduced and analyzed at different observatories in Europe. A reduction program package allows manipulation and display of the data. After the initial reduction all tape output from the reduction programs uses the same tape format regardless of the program. Transportation of data between observatories is done via magnetic tape with the same standard format. For data transportation to observatories not normally using Westerbork information a common tape format has been developed. Suggestions to alleviate problems with this data transfer are discussed.
The distance scale beyond the Local Group – A progress report on work in the southern hemisphere
Authors: Smith Malcolm G. 
Published: July 2016

Afin d’éviter la répétition du contenu de nombreuses revues récentes, cette contribution rapporte principalement les projets d’étude au-delà du groupe local, en cours de réalisation dans l’hémisphère Sud.La majeure partie de ce travail n’ayant commencée que récemment, les résultats sont préliminaires. Divers sujets sont traités: le groupe du Sculpteur (§ II), des groupes proches de l’hémisphère Sud et des galaxies de champ (§ III), ainsi que les distances des amas denses les plus proches de l’hémisphère Sud. D’autres travaux seront cités dans certaines revues de la conférence: (i) les études sur les nuages de Magellan, et d’autres objets du groupe local, (ii) les problèmes d’anisotropie de l’expansion de Hubble, (iii) les estimations des distances des objets quasi stellai-res.
Spectroscopy and the Hubble diagram of faint radio galaxies
Authors: Spinrad Hyron , Smith Harding E. 
Published: July 2016

RésuméL’ÉTUDE SPECTRALE ET LE DIAGRAMME DE HUBBLE DES RADIOGALAXIESNous discutons les identifications récentes et les observations des radiogalaxies faibles, au décalage spectrale z = 0.75, en les présentant dans des diagrammes Hubble.
A search for neutral hydrogen in primordial protoclusters
Authors: Davies R. D. , Pedlar A. 
Published: July 2016

Résumé:La prévision de Sunyaev et Zel’dovich que les proto-amas peuvent passer par une phase d’hydrogène neutre pendant leur formation a été testée par la recherche de leur émission de la raie d’hydrogène décalée vers le rouge. Des limites supérieures comprises entre 0. 07 et 0. 17 °K ont été obtenues dans une bande de 2. 5 MHz à 327 MHz ce qui correspond à un décalage vers le rouge de z = 3.33. Ces résultats indiquent qu’il ne peut pas exister plus de proto-amas d’hydrogène que la quantité calculée par ces auteurs.
The “conventional” view of redshifts
Authors: Rees M. O. 
Published: July 2016

Exposé du point de vue “conventionnel” sur les décalages vers le rouge.In Peebles’ well-known textbook, one chapter is entitled “a child’s garden of cosmological models”. Maybe a “jungle” would better describe the lush diversity of theories expounded at this exceptionally interesting conference. If there is a dominant orthodoxy in cosmology, the proceedings here have successfully obscured it – a participant without prior exposure to the subject would not have gleaned from this week’s discussions what views were “conventional” and what were not. Anyway, I presume that my brief is to assess the status of the cosmological views that would commend themselves to Peebles and his like: that is to say, the package of ideas in which there was a “hot big bang”, galaxies and clusters condensed via gravitational instability, the quasar phenomenon is related to galactic nuclei, and all large redshifts (except perhaps quasar absorption lines) are due to the expansion of the universe. This, at least, is the framework within which we “conventional” people attempt to interpret the data – or (in the view of some “radicals”) the self-imposed blinkers by which our vision is confined.
Historical Introduction
Authors: Freeman K.C. 
Published: July 2016

AbstractOur ideas about the surface brightness distribution of galaxies has changed greatly since 1970. I contrast the view at that time with our present view of the subject, and then briefly discuss some topics in the studies of Low Surface Brightness Galaxies (LSBG) that I think are particularly interesting: the Tully-Fisher relation, LSBG as systems of high angular momentum, LSBG in clusters of galaxies, and the potential impact of the HIPASS survey.
The Space Density of Spiral Galaxies as function of their Luminosity, Surface Brightness and Scalesize
Authors: de Jong Roelof S. , Lacey Cedric 
Published: July 2016

AbstractThe local space density of galaxies as a function of their basic structural parameters -like luminosity, surface brightness and scalesize-is still poorly known. Our poor knowledge is mainly the result of strong selection biases against low surface brightness and small scalesize galaxies in any optically selected sample. We show that in order to correct for selection biases one has to obtain accurate surface photometry and distance estimates for a large (≳ 1000) sample of galaxies. We derive bivariate space density distributions in the (scalesize, surface brightness)-plane and the (luminosity, scalesize)-plane for a sample of ~1000 local Sb-Sdm spiral galaxies. We present a parameterization of these bivariate distributions, based on a Schechter type luminosity function and a log-normal scalesize distribution at a given luminosity. We show how surface brightness limits and (1+z)4 cosmological redshift dimming can influence interpretation of luminosity function determinations and deep galaxy counts.
Low Surface Brightness Dwarf Galaxies in the Bristol – Anglo-Australian Observatory Virgo Cluster Survey
Authors: Jones J.B. , Phillipps S. , Schwartzenberg J.M. , Parker Q.A. 
Published: July 2016

AbstractWe describe a new, deep photographic survey of the Virgo Cluster which uses multiple exposures on Tech Pan film with the United Kingdom Schmidt Telescope to probe the dwarf population to fainter surface brightness limits than previous surveys. We have identified galaxies having sizes (≥ 3 arcsec scale length) and surface brightnesses (≤ 24.5 R mag arcsec−2) characteristic of those expected for dwarf spheroidal galaxies in the cluster. The survey is providing substantial samples of extremely low luminosity galaxies outside the environment of the Local Group and nearby groups for the first time. An initial study of two small areas has found dwarf spheroidal candidates in large numbers (500 deg−2) which indicate a steep, continuously rising luminosity function at low luminosities.
Counting the Ghosts: Optical Field Surveys for Low Surface Brightness Galaxies
Authors: Dalcanton Julianne J. 
Published: July 2016

AbstractGiven the difficulties in detecting even a single LSB, surveying statistically significant numbers of LSBs presents a daunting task. Large, systematic surveys with well understood selection criteria are necessary for assessing the full cosmological significance of the LSB population. Here I briefly review some of the progress which has been made in the last ten years, and suggest strategies which may prove fruitful in the future.
Environmental Effects on the Faint End of the Luminosity Function
Authors: Phillipps S. , Jones J.B. , Smith R.M. , Couch W.J. , Driver S.P. 
Published: July 2016

AbstractRecent studies have demonstrated that many galaxy clusters have luminosity functions (LFs) which are steep at the faint end. However, it is equally clear that not all clusters have identical LFs. In this paper we explore whether the variation in LF shape correlates with other cluster or environmental properties.