arXiv subjects

Sally D. Hunsberger

Publications and source records attributed to Sally D. Hunsberger.

3 recordsLinked to original sources

arXiv2000

Identifying Old Tidal Dwarf Irregulars

We examine the observational consequences of the two possible origins for irregular galaxies: formation from collapse of a primordial cloud of gas early in the age of the Universe, and formation from tidal tails in an interaction that could have occured any time in the history of the Universe. Because the formation from tidal tails could have occurred a long time ago, proximity to larger galaxies is not sufficient to distinguish tidal dwarfs from traditional dwarfs. We consider the effects of little or no dark matter on rotation speeds and the Tully-Fisher relationship, the metallicity-luminosity relationship, structure, and stellar populations. From these selection criteria, we identify a small list of dwarf irregular galaxies that are candidates for having formed as tidal dwarfs.

astro-ph↗

arXiv1998

The Luminosity Function of Galaxies in Compact Groups

From R-band images of 39 Hickson compact groups (HCGs), we use galaxy counts to determine a luminosity function extending to M_R=-14.0, approximately two magnitudes deeper than previous compact group luminosity functions. We find that a single Schechter function is a poor fit to the data, so we fit a composite function consisting of separate Schechter functions for the bright and faint galaxies. The bright end is best fit with M^*=-21.6 and alpha=-0.52 and the faint end with M^*=-16.1 and alpha=-1.17. The decreasing bright end slope implies a deficit of intermediate luminosity galaxies in our sample of HCGs and the faint end slope is slightly steeper than that reported for earlier HCG luminosity functions. Furthermore, luminosity functions of subsets of our sample reveal more substantial dwarf populations for groups with x-ray halos, groups with tidal dwarf candidates, and groups with a dominant elliptical or lenticular galaxy. Collectively, these results support the hypothesis that within compact groups, the initial dwarf galaxy population is replenished by "subsequent generations" formed in the tidal debris of giant galaxy interactions.

astro-ph↗

arXiv1995

The Formation of Dwarf Galaxies in Tidal Debris: A Study of the Compact Group Environment

From R-band images of 42 Hickson compact groups, we present a sample of 47 candidate dwarf galaxies that are associated with the tidal tails and arms in the groups. The candidates, found in 15 tidal features, have R magnitudes and masses (for M/L = 1) in the ranges -16.5 < M_R - 5 log h_{75} < -11.5 and 2x10^6 M_{\odot} < M < 2x10^8 M_{\odot}, respectively. Their masses and locations are compared to the predictions of theoretical/N-body tidal dwarf formation scenarios. Considering the longevity of tidal debris in the compact group environment and the results of this survey, we estimate the contribution of the tidal dwarf formation mechanism to the population of dwarf galaxies observed at large in compact groups. If the majority of our dwarf galaxy candidates are confirmed as being gravitationally bound stellar systems, then a significant fraction, perhaps as much as one-half, of the dwarf population in compact groups is the product of interactions among giant parent galaxies.

astro-ph↗