/ 98 05 17 4 v 1 1 3 M ay 1 99 8 The Luminosity Function of Galaxies in Compact Groups 1

From R-band images of 39 Hickson compact groups (HCGs), we use galaxy counts to determine a luminosity function extending to MR = −14.0 + 5 log h75, approximately two magnitudes deeper than previous compact group luminosity functions. We find that a single Schechter function (Schechter 1976) is a poor fit (χν > 4) 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 α = −0.52 and the faint end with M = −16.1 and α = −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. Subject headings: galaxies — luminosity function, compact groups, evolution Observations were made on the 60 inch telescope at Palomar Mountain, which is jointly operated by the California Institute of Technology and the Carnegie Institution of Washington. Center for Gravitational Physics and Geometry, Pennsylvania State University Alfred P. Sloan Research Fellow 2 Hunsberger, Charlton, & Zaritsky Luminosity Function of HCG Galaxies