DWARF GALAXIES IN THE COMA CLUSTER

Two catalogues of galaxy morphology for the Coma cluster, one magnitude limited and the other diameter limited, are used to investigate the properties of dwarf galaxies in Coma, the densest of the nearby cluster environments. Both surveys cover an area of 3.97 square degrees. The magnitude limited sample is complete to m(b) = 20.0, and the diameter limited survey is complete to 9 arcsec. The source for the galaxy magnitudes-Godwin et al. [MNRAS, 202, 113 (1983)]-also provides (b - r) galaxy colors for approximately 90% of the sample. We discuss the radial distribution of all dwarf galaxies in the Coma cluster after sorting them by morphological type: dwarf irregular, dwarf elliptical, and dwarf spheroidal, and based on these distributions assert that (1) dwarf irregulars are not cluster members, (2) dwarf ellipticals track the distribution of E and SO galaxies, and (3) the population of dwarf spheroidal galaxies, while tracking the E and SO population in the cluster, has been destroyed in the cluster core. The evidence for dwarf spheroidal destruction can be used to place an upper limit on the internal stellar velocity dispersion for the Coma dwarf spheroidals. We show that the total early-type galaxy luminosity function (E + SO + dE + dSph) is statistically incompatible with a standard Shechter luminosity function and that the bright portion of the luminosity function follows a log-normal distribution. Finally, we show that the ratio of dwarfs to giants in Coma is no larger than that in the Virgo cluster and therefore that the dwarf-to-giant ratio ceases to increase with increasing cluster richness.