A detailed study of dwarf galaxies in the core of the Coma Cluster

Abstract

In an earlier paper, we determined the morphological types of galaxies in the Coma Cluster using data from the HST/ACS Coma Cluster treasury survey. Of the 132 members, 51 are non-dwarfs and 81 are dwarfs. We define dwarfs to have an absolute luminosity MF814W≥-18.5 as in Marinova et al. (2012). In this paper, we identify the morphological types of these dwarf galaxies and conduct a detailed study of their properties. Using GALFIT, we determined the structural properties of our sample, and with spectroscopic redshifts, we determined memberships and distances to identify dwarfs. A visual examination of the residual images reveals that our sample of 78 dwarf galaxies comprises dwarf lenticular (dS0) 22%, dwarf elliptical (dE) 69%, dwarf spirals (dSp) 4%, dwarf ring (dring) 1%, dwarf barred spirals (dSBp) 3% and dwarf irregular (dIrr) 1% galaxies. The bulge-disk decomposition (Sérsic + exponential) fits are only good for the dS0 galaxies. The remainder of the sample gives good fits only for single Sérsic fits. The color-magnitude relation (CMR) shows that the dEs are redder and fainter than the rest of the sample (except one dIrr galaxy). The Kormendy relation reveals that dE galaxies have lower surface brightness than the rest of the sample. Our research leads us to conclude that dwarf galaxies appear to have a different formation and evolution process than non-dwarf galaxies.