DWARF GALAXIES IN THE COMA CLUSTER - II - PHOTOMETRY AND ANALYSIS

We use the dataset derived in our previous paper (Seeker and Harris 19 97) to study the dwarf galaxy population in the central similar or equ al to 700 arcmin(2) of the Coma cluster, the majority of which are ear ly-type dwarf elliptical (dE) galaxies. Analysis of the statistically decontaminated dE galaxy sequence in the color-magnitude diagram revea ls that the mean dE color at R = 18.0 mag is (B - R) similar or equal to 1.4 mag, but that a highly significant trend of color with magnitud e exists [Delta(B - R)/Delta R = -0.056 +/- 0.002 mag] in the sense th at fainter dEs are bluer and thus presumably more metal poor. The mean color of the faintest dEs in our sample is (B - R) similar or equal t o 1.15 mag, consistent with a color measurement of the diffuse intracl uster light in the Coma core. This intracluster light could then have originated from the tidal disruption of faint dEs in the cluster core. The total galaxy luminosity function (LF) is well modeled as the sum of a log-normal distribution for the giant galaxies, and a Schechter f unction for the dE galaxies with a faint-end slope alpha = -1.41 +/- 0 .05. This value of alpha is consistent with those measured for the Vir go and Fornax clusters. The spatial distribution of the faint dE galax ies (19.0 < R less than or equal to 22.5 mag) is well fit by a standar d King model with a central surface density of Sigma(0) = 1.17 dEs arc min(-2) and a core radius R-c = 22.15 arcmin (similar or equal to 0.46 h(-1) Mpc). This core is significantly larger than the R-c = 13.71 arc min (similar or equal to 0.29h(-1) Mpc) found for the cluster giants a nd the brighter dEs (R less than or equal to 19.0 mag), again consiste nt with the idea that faint dEs in the dense core have been disrupted. Finally, we find that most dEs belong to the general Coma cluster pot ential rather than as satellites of individual giant galaxies: An anal ysis of the number counts around ten cluster giants reveals that they each have on average 4 +/- 1 dE companions within a projected radius o f 13.9h(-1) kpc.