bluuebunny/crossref_metadata_2025_split huggingface dataset:
21 - cm observations of redshifts and their implications for the distance scale
Authors: Tully R. Brent , Fisher J. Richard 
Published: July 2016

RésuméIl existe une corrélation étroite entre la largeur de la raie d’hydrogène neutre à 21 cm et la luminosité des galaxies spirales ainsi qu’entre cette largeur et le diamètre des galaxies spirales. Elle existe pour un échantillon de spirales proches dont la distance est calibrée par les céphéides, ainsi que pour des spirales dans quelques amas. La comparaison entre ces deux relations nous donne la distance de l’amas et une valeur pour la constante de Hubble. Pour l’amas de Virgo la méthode nous donne une distance de 14, 5Mpc, donc Ho = 77 km/s/Mpc. Pour 1’ amas de la Grande Ourse, une distance de 12, 6 Mpc, donc Ho = 75 km/s/Mpc. Il faut signaler qu’on trouve ces résultats avec des galaxies vues plutôt par la tranche. Il existe une différence systématique: avec les galaxies vue de face on trouve des distances plus grandes. Pour les galaxies de champ la corrélation existe, bien que la dispersion augmente. Avec 74 galaxies des types Sc-Sd et d’inclinaison 45°-75° on trouve Ho = 80 km/s/Mpc, avec celles situées dans l’amas supergalactique on trouve Ho = 75, et avec celles hors de l’amas supergalactique on trouve Ho = 90 km/s/Mpc. Cette différence est significative à 2 sigma près.
Dynamical state of pairs of galaxies
Authors: Karachentsev I. D. 
Published: July 2016

Les estimations de masses de galaxies doubles sont obtenues sur la base des observations récentes de 148 paires de galaxies pour lesquelles les vitesses radiales des deux composantes ont été mesurées.On montre que le rapport masse orbitale moyenne sur luminosité dépend essentiellement du type morphologique des galaxies doubles et du type d’interaction entre les deux composantes de la paire. Les valeurs minimales de ce rapport sont obtenues pour les galaxies doubles dont les caractéristiques d’interaction sont linéaires, à savoir: ponts, queues, ainsi que pour les paires avec des composantes compactes et des galaxies de Markarian,La relation empirique entre le rapport masse-luminosité et la séparation spatiale des composantes de paires ne montre pas de façon évidente l’existence de halos stellaires cachés autour des galaxies doubles,
Constraints on the Unseen Galaxy Population from the Lyα Forest
Authors: M. Lanzetta Kenneth , Chen Hsiao-Wen , Webb John K. , Barcons Xavier 
Published: July 2016

AbstractHere we describe results of our attempt to determine what types of galaxies are responsible for the Lyα forest absorption systems, based on our ongoing imaging and spectroscopic survey of faint galaxies in fields of HST spectroscopic target QSOs. Our primary conclusions are that the bulk of the Lyα forest arises in more or less normal galaxies (that span the normal range of luminosity and morphology) and that any “unseen” low surface brightness galaxies are unlikely to contribute significantly to the luminosity density of the universe.
Low Luminosity Galaxies in Large Surveys
Authors: Huchra John P. 
Published: July 2016

AbstractThe debate about the slope and amplitude of the galaxy luminosity function at the faint end is discussed w.r.t. faint galaxies in large surveys, in particular the second CfA (CfA2) and the Las Campanas (LCRS) redshift surveys. Large surveys are necessary to determine the statistics of rare objects or objects that can only be seen out to limited volumes. Both surveys show excesses of faint galaxies over Schechter function fits, but the parent sample for the LCRS survey generally does not contain large or low surface brightness galaxies which do appear in the CfA2 survey. The objects that comprise the relatively large excess of faint galaxies in the CfA2 survey are shown to be primarily of low surface brightness and late morphological type and are generally emission line galaxies. Galaxy samples constructed like the LCRS will generally always be deficient in low luminosity galaxies and thus are not useful for constraining the faint end of the galaxy luminosity function.
The Faint End of the Galaxy Luminosity Function in Rich Clusters
Authors: Smith R.M. , Phillips S. , Driver S.P. , Couch W.J. 
Published: July 2016

AbstractRecent results on the determination of the shape of the faint end of the galaxy luminosity function in rich clusters are discussed. There is increasing evidence that in many cases the faint end of the function is steep, indicating a large population of dwarf, possibly low surface-brightness, galaxies. In addition, the magnitude at which the turn-up appears is approximately constant with richness and distance. However, it is clear that not all clusters show such a feature.
A Survey for Low Surface Brightness Dwarf Galaxies Around M31
Authors: Armandroff Taft E. , Davies James E. , Jacoby George H. 
Published: July 2016

AbstractBy applying a digital filtering technique to 1550 deg2 of the POSS-II in the vicinity of M31, we found two previously unidentified very low surface brightness dwarf galaxies which we designate And V and VI. Follow-up imaging with the KPNO 4-m telescope resolved these into stars easily. The V- and I- band images of And V indicate a distance similar to that of M31, and <[Fe/H]> ~ −1.5. All evidence strongly supports its classification as a dwarf spheroidal companion to M31. Data for And VI are being analyzed, but preliminary indications support a similar conclusion. Our search for more dwarfs, including follow-up observations of numerous candidates found via digital filtering, is incomplete; thus, further identifications may be forthcoming.
Dwarf Galaxies in Nearby Groups
Authors: Bremnes T. , Binggeli B. , Prugniel P. 
Published: July 2016

AbstractWe present preliminary results from two observing campaigns where global photometric data for most dwarf galaxies in the M81 and M101 groups as well as some field dwarfs were obtained. The galaxies in the denser M81 group are more often of dwarf elliptical type and are redder and fainter than those of the M101 group and surrounding field, which are mostly of the dwarf irregular types. But both types follow the same total magnitude - central surface brightness relation, so there might be an evolutionary connection between the two classes.
The Extreme Outer Regions of Disk Galaxies: Star Formation and Metal Abundances
Authors: Ferguson Annette , Wyse Rosemary , Gallagher Jay 
Published: July 2016

AbstractThe extreme outer regions of disk galaxies, lying at or beyond the classical optical radius defined by R25, present an opportunity to study star formation and chemical evolution under unique physical conditions, possibly reminscent of those which existed during the early stages of disk evolution. We present here some of the first results from a large study to measure star formation rates and metallicities in the extreme outer limits of a sample of nearby spiral galaxies. Despite their low gas column densities, massive star formation is often observed in these outer parts, but at an azimuthally–averaged rate much lower than that seen in the inner disk. Gas-phase O/H abundances of roughly 10% solar characterize the gas at 1.5–2 R25. The implications of our results for star formation ‘laws’ and models of disk evolution are discussed.
The Low Surface Brightness Galaxy HIPASS1126-72
Authors: Kilborn Virginia , de Blok Erwin , Staveley-Smith Lister , Webster Rachel 
Published: July 2016

AbstractThe low surface brightness galaxy HIPASS1126-72 was detected in the HI Parkes All Sky Survey (HIPASS). The galaxy was previously listed in the Southern Galaxy Catalogue under the name SGC1124.87221. This galaxy represents a class of galaxies that we will readily detect in the HIPASS survey, which have low surface brightness in the optical, but are easily detectable in neutral hydrogen.
What Causes the HI Holes in Gas-Rich LSB Dwarfs?
Authors: Rhode Katherine L. , Salzer John J. , Westpfahl David J. 
Published: July 2016

AbstractWe have carried out a deep, multi-color imaging study of Holmberg II (Ho II) and several other nearby LSB dwarf galaxies for which detailed HI maps exist. The formation of the HI holes in these galaxies has been attributed to multiple supernovae (SNe) occurring within windblown shells around young, massive star clusters. To search for evidence of the clusters, we have compared optical images with the HI maps and measured magnitudes and colors of objects in and around the HI holes.Although the SN scenario requires that detectable star clusters should often be present in the centers of the HI holes, our observations have in most cases failed to reveal these clusters at the expected magnitudes. In fact, many of the HI holes are located in regions of very low optical surface brightness, which show no evidence of recent star formation.
The Structure of the Multi-Phase ISM in Low Surface Brightness Galaxies
Authors: Spaans M. 
Published: July 2016

AbstractThe multi-phase structure of the interstellar medium in low surface brightness galaxies is investigated and compared to observations. It is found that the ambient pressure and metallicity very strongly influence the abundances of molecular hydrogen and carbon monoxide. The emissivity of the latter is computed and found to agree naturally with the upper limits measured for low surface brightness galaxies. The implications for star formation efficiency and galaxy evolution are discussed.
The HST/LCO Measurement of the Optical Extragalactic Background Light
Authors: Bernstein R.A. 
Published: July 2016

AbstractWe present the first detection of the mean flux of the optical extragalactic background light (EBL) at 3000, 5500, and 8000Å, derived from coordinated data sets from HST and Las Campanas Observatory. To isolate the extragalactic component, we have measured and subtracted the flux from foreground sources explicitly. In addition to detections in all three bands, we identify the minimum surface brightness contributed by resolved galaxies (23 < V < 28 AB mag) using a non-standard method of aperture photometry to which these data are uniquely suited. Individually resolved galaxies account for ~ 30% of the mean EBL coming from galaxies fainter than V = 23 AB mag. Taking into account the effective surface brightness detection limits of the deepest galaxy counts, and the results of LSB surveys at low redshift, the EBL we detect can be explained by galaxy populations already cataloged.
Detecting the Low Surface Brightness Universe: the Extragalactic Background Light and LSB Galaxies
Authors: Väisänen P. , Tollestrup E.V. 
Published: July 2016

AbstractIndividual sources are detected ideally to a confusion limit at a given wavelength, but there is still much information beyond that. Absolute background brightness measurements provide a crucial constraint to models describing the undetected population of sources in the distant – and/or low surface brightness – universe. We calculate how much low surface brightness galaxies (LSB) would contribute to the the overall extragalactic background light (EBL) and review the status of EBL measurements in the optical and infrared wavelengths. To be able to push deeper the detection limits on very faint sources a fluctuation analysis method is introduced. The use of these different approaches together is essential when studying the very faint and low surface brightness universe.
The Complex Kinematics of Galaxies in Hickson 67
Authors: Bettoni D. , Buson L. M. 
Published: July 2016

AbstractThe kinematics of galaxies belonging to the Hickson compact group HCG67 are investigated. The latter consists of four galaxies, three of which (a, c, d) are embedded in a common envelope. The fourth galaxy (b) is a spiral that is detected both in radio and in IR wave-bands. Our observations show that the three galaxies in apparent interaction are probably caught during an ongoing merger process.
HI Image Synthesis of Southern Compact Groups
Authors: Babic B. , Price R. M. , Jones K. 
Published: July 2016

AbstractFour southern compact groups, the Hickson Compact Groups HCG 22 and HCG 26 (Hickson 1982), and the groups AM 1238–396 and ESO 410-G(024—026) have been imaged in HI, along with 12cm continuum using the Australia Telescope Compact Array (ATCA). The initial findings for the latter two groups are presented here. While ESO 410-G is not in fact a physical group, due to the discordant redshifts amongst the members, it is however presented here.Overall for all the groups we find no other sources of HI in the field that might indicate that these are part of a larger loose group structure. This is not always the case, as with HCG 23 (Williams 1995) and HCG 95 (Hutchmeier 1999), both of whom find additional Hɪ sources within the primary beam accordant with the compact group’s velocity.The HI is also clearly associated with each of the individual member galaxies in all cases, except for HCG 26, which envelopes the whole group as was also shown by Williams and van Gorkom (Williams 1995).
Small Group Dynamics and Extended Gas
Authors: Combes F. 
Published: July 2016

AbstractInteractions between galaxies have spectacular effects on gas dynamics, and small galaxy groups are a privileged place to investigate them. In particular, they could test the existence of cold H2 gas as dark matter in the outer parts of galaxies. HI observations have revealed that galaxies in small groups are deficient in atomic gas, like in richer galaxy clusters such as Virgo, although in a lesser extent. Galaxy interactions could be the cause of this deficiency, stripping the gas out of galaxies and enriching the inter-cluster medium (ICM) in hot gas, which in turn strips gas through ram pressure. Alternatively, the gas present at the formation of the group could have been heated to its virial temperature, and be observed now as X-rays. The dynamical processes related to this extended gas in small galaxy groups are reviewed.
New Dwarf Galaxies in the IC342/Maffei Group
Authors: Huchtmeier W. K. , Karachentsev I. D. , Karachentseva V. E. 
Published: July 2016

AbstractThis is a report on the detection of HI emission from three ‘new’ dwarf galaxies Perseus A, Perseus B, and Camelopardalis D in the IC342/Maffei group of galaxies and of Draco A. The actual number of (probable) member galaxies of this group increases to 19 galaxies. Its velocity dispersion is 86 kms−1. With a distance of 2.2±0.5 Mpc this group is the nearest to the Local Group and might have considerable dynamical influence on the Local Group.
Compact Galaxy Groups in the South
Authors: Price R. M. , Babic B. , Jones K. 
Published: July 2016

Compact groups are intermediate between single and binary galaxy systems, and clusters of galaxies. Because of their small numbers of members, and the small separations between the members of each group, they are good candidates for the study of galaxy interactions and mergers. In particular, high resolution imaging of these systems in neutral hydrogen can yield important data on interactions between galaxies.The radio telescopes of the Australian National Telescope Facility (ATNF) are especially well suited to the study of neutral hydrogen gas in these systems. The Parkes 64-m telescope has a 15 arcminute FWHM beam at 21 centimeters wavelength which is sufficient to include the sky area of a typical compact group. Parkes was used for detection of HI in nine southern groups and for determination of their approximate velocities, if not previously known. Follow-up observations with the ATNF Compact Array synthesis telescope provided high resolution (20 arcsecond) images with appropriate frequency resolution to determine velocity fields for the gas distribution.
On the Nature of Compact Groups of Galaxies
Authors: de Carvalho Reinaldo R. 
Published: July 2016

AbstractBased on the spectroscopic survey of de Carvalho et al. (1997), we analyse the structural and dynamical properties of 17 Hickson Compact Groups (HCG). This analysis probes a region of 0.5° × 0.5° around each group and shows that most are part of larger structures. Our results also suggest that the Hickson sample is composed of different dynamical stages of the group’s evolution. Specifically, we identify three possible evolutionary phases among groups in the sample: loose groups, [core+halo] systems and compact groups, each one presenting a distinct surface density profile. This sequence is consistent with the replenishment scenario for the formation and evolution of compact groups within larger and less dense systems.
N-body simulations of interactions and mergings in small galaxy groups
Authors: Athanassoula E. 
Published: July 2016

AbstractIn this paper I focus on three topics related to the dynamical evolution of small galaxy groups, for which the input of N-body simulations has been decisive. These are the merging rates in compact groups, the properties of remnants of multiple mergers, and the evolution of disc galaxies surrounded by one or more satellites. The short dynamical times of compact groups make it difficult to understand why such groups are observed at all. N-body simulations have pointed out two possible classes of solutions to this problem. The first one proposes that there is ongoing formation of compact groups, or that the longevity of the group is due to secondary infall. For the second class of solutions the longevity of compact groups is due either to their specific initial conditions, or to a massive common halo, encompassing the whole group. I discuss here these alternatives, together with their respective advantages and disadvantages. I then turn to the structure of remnants of multiple mergers and compare the results of N-body simulations with the properties of observed elliptical galaxies. Finally I discuss the dynamical evolution of a disc galaxy surrounded by one or more spherical satellites.
A Numerical Experiment of a Triple Merger of Spirals
Authors: Aceves Héctor 
Published: July 2016

Several studies have addressed the topic of spiral interactions in pairs or in small groups (Barnes 1998). However there is no specific study, to our knowledge, of interacting triplets of spirals. Here we present a preliminary report of ongoing research on the dynamics of triplets that includes galaxies of different morphology. In particular we follow a triplet of equal-mass spirals until a merger remnant that resembles an elliptical-like galaxy has been formed.It is known that the HI component of spirals is a good tracer of interactions. Indeed, several triplets (e.g. in M81 group) that do not appear to be perturbed in optical images do so in H I maps. Although a self-consistent treatment of gas requires the inclusion of e.g. pressure forces, we use here a test-particle approach to study it during a triple interaction of spirals; this can yield information about the large-scale kinematical features of gaseous tails.
Binary Galaxy Spin Correlations in Small Galaxy Groups
Authors: Wirén S. , Valtonen M. J. , Liu B. 
Published: July 2016

AbstractStatistics of spin orientations in binary galaxies may be used as a tool to study the formation process of galaxies. Helou (1984) found that the spins of spiral galaxies in binary systems are anticorrelated, and he suggested that it may have to do with the inclination dependence of the galaxy merger process. We study this dependence in small groups of galaxies. An N-body code is developed which uses an inclination dependent dynamical friction law to affect mergers of galaxies. It is found that some correlation results in this way in groups, which have initially random spin orientations.
Dynamics and Merging in Compact Galaxy Groups
Authors: Zheng J.-Q. , Valtonen M. J. , Chernin A. D. , Wiren S. 
Published: July 2016

AbstractBy using a few body code with a frictional force we study the dynamics of small galaxy groups. The results have been compared with observational data on triples and binaries by Karachentsev et al. We start with four to five galaxy groups initially and take samples of the groups when the membership has dropped to two or three. It is possible to find merger evolution models which agree with observations. One interesting factor is the mass-to-light ratio of the observed systems: we find the best fit with the models when the mass-to-light ratio is about 50 in solar units.
Black hole ejections in mergers of small groups of galaxies
Authors: Heinämäki Pekka , Valtonen Mauri 
Published: July 2016

AbstractThe formation of a multiple black hole system via merging processes of galaxies is simulated. Starting from the hierarchical halo merger model by Lacey and Cole (1993) and the general assumption that supermassive black holes (> 106M⊙) are common in the nuclei of galaxies we followed the formation of a four black hole system. Ultimately, instability of the four body system led to 835 symmetric two-sided slingshot ejections out of 10,000 simulations. This result was applied to the most straightforward application of the slingshot process, namely to the origin of extended radio sources.
Tidal Perturbation and Active Galaxy Nuclei
Authors: Byrd Gene , Valtonen Mauri 
Published: July 2016

AbstractTheories of nuclear activity mechanisms in disk galaxies (such as Seyfert galaxies) range from intrinsic (e.g. bars) to external (tidal perturbation by passing companions). The Byrd et al. (1986, 1987) simulation survey determined the tidal perturbation necessary to induce nuclear activity. Observational surveys have raised doubt as to the tidal explanation of Seyfert-type activity in galaxies with some suggesting a weak or nonexistent correlation between tidal perturbation and Seyfert activity compared to a normal sample. The simulations show a several hundred million year delay in the appearance of activity after perturbation and a similar duration which can explain these null results. For double galaxies, we derive from the tidal hypothesis that: (1) There should be an excess of pairs where both are active over pairs with one active. (2) Nuclear activity will be preferentially excluded from pairs which are unequal and favorably distributed to pairs where the members are equal. (3) The size of pair members to create activity can be smaller if the pair members are equal in size than if they are unequal. (4) Pairs where one or both members are active should have a smaller velocity difference times separation than if both are normal. All the predictions are seen in observations of activity in Karachentsev’s (1983) list of double galaxies. Optimally, statistical studies of nuclear activity and companions should include their sizes, separations, and radial velocities relative to the primary. The study by Dultzin-Hacyan et al. (1999) which finds an excess of large companions around Seyfert 2 galaxies is a step in the right direction.
Wide triplets of galaxies
Authors: Chernin A. D. , Dolgachev V. P. , Domozhilova L. M. 
Published: July 2016

AbstractTriple systems of galaxies with the typical mass ∼ 10h13M⊙ and crossing time about the Hubble time provide evidence for ongoing collapse on the space scale ∼ 1 Mpc. This is confirmed by a set of computer simulations with the use of free-fall models.