AAS 201st Meeting, January, 2003
Session 116. Galaxies - Activating
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

## [116.10] A Census of the Dwarf Galaxies in Stephan's Quintet Including New Tidal Dwarf Galaxy Candidates

C. Palma, S.D. Hunsberger, J.C. Charlton, P.R. Durrell (Penn State), S.C. Gallagher (MIT Center for Space Research)

We present a mosaic of two \textit{Hubble Space Telescope} pointings in Stephan's Quintet (Hickson Compact Group 92). These WFPC2 B (F450W), V (F569W) and I (F814W) images cover NGC 7319, its associated tidal tail, NGC 7318A/B, and the tidal debris just north of NGC 7318A/B. Using the detection algorithm in the FOCAS software package, we have identified 68 dwarf galaxy-sized objects within the surveyed portion of the compact group.

The high resolution \textit{HST} images reveal that 13 of these objects are probable background galaxies, leaving 55 candidate dwarf galaxy members of the compact group. Many (21) of these candidate dwarf galaxies are blue star forming regions in the tidal debris surrounding NGC 7318A/B that are known to be bright H-\alpha sources from ground-based imaging. Among the remaining candidate dwarf galaxies, there are also 12 objects found within the bright isophotes of the NGC 7319 tidal tail that we consider tidal dwarf candidates. Thus, 33 out of 55 candidate dwarfs in the Quintet are found in the optically bright tidal debris regions.

However, even among the 22 candidate dwarf galaxies found outside of the bright optical tidal tails, we identify several of these as new \textit{tidal dwarf galaxy} candidates. Recent VLA maps of the Quintet show that the NGC 7319 tidal tail has a significant H\textsc{I} component (the Arc-N'' feature) that extends further north than the optical tail. There are several dwarf galaxy candidates \textit{outside} the optical tail that appear to be associated with features in the H\textsc{I} tail, which suggests that these dwarfs may be tidal dwarf galaxies, too. Since optical surveys of interacting galaxies are likely to misclassify tidal dwarf galaxies that are similar to those in the H\textsc{I} tail of the Quintet, we suggest that the importance of the tidal dwarf phenomenon may be underestimated.

We acknowledge support for this work from the NSF and from STScI.