Dwarf Galaxy Formation in the Compact Group Environment

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Session 114 -- Compact Groups, Galaxy and Quasar Clustering
Oral presentation, Thursday, 12, 1995, 10:00am - 11:30am

[114.04] Dwarf Galaxy Formation in the Compact Group Environment

S. D. Hunsberger (Penn State), J. C. Charlton (Penn State), D. Zaritsky (UCO/Lick Observatory, UC Santa Cruz)

Because dwarf galaxies are the dominant type of galaxy in the Universe, the formation process of dwarf galaxies is at least as equally important as that of the giants. The dwarf population is not merely an extension of giants to fainter luminosites; fundamental differences between these classes (Kormendy 1985, Binggeli 1985) suggest different formation mechanisms. Recent analytic calculations and N-body simulations (Elmegreen et al. 1993, Barnes \& Hernquist 1992) predict that star-forming clumps with masses comparable to those of dwarf galaxies can form in the tidal debris from galaxy interactions. Examples of such clumps are observed in the tidal tails of the Antennae and Superantennae systems (Mirabel et al. 1992, Mirabel et al. 1991). \par The high space density of galaxies in compact groups makes them a unique environment in which to systematically examine the formation and evolution of dwarf galaxies. Mergers and interactions are frequent and tidal debris is common. We obtained R band images of 42 Hickson compact groups and identified 40 possible dwarfs in 7 of the 42 groups which exhibit noticeable tidal interaction. The median magnitude of the dwarf candidates is $-14.3$ and the range of magnitudes is $-16.0 \le M_R \le -13.0$. With these results, we estimate the number of dwarfs expected to form over the lifetime of a group and find it comparable to an estimate of the total number of dwarfs presently observed in a group. By using these data to better understand the tidal origin of dwarf galaxies and then expanding the study to other environments, we will determine the fraction of all dwarfs that may have formed as a result of tidal interactions.

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