The distribution of early- and late-type galaxies in the coma cluster

The spatial distribution and the morphology-density relation of Coma cluster galaxies are studied using a new homogeneous photometric sample of 450 galaxies down to B = 16.0 mag with quantitative morphology classification. The sample covers a wide area (10°×10°), extending well beyond the Coma cluster. Morphological classifications into early- (E+S0) and late- (S) type galaxies are made by an automated algorithm using simple photometric parameters, with which the misclassification rate is expected to be approximately 10% with respect to early and late types given in the Third Reference Catalogue of Bright Galaxies. The flattened distribution of Coma cluster galaxies, as noted in previous studies, is most conspicuously seen if the early-type galaxies are selected. Early-type galaxies are distributed in a thick filament extended from the NE to the WSW direction that delineates a part of large-scale structure. Spiral galaxies show a distribution with a modest density gradient toward the cluster center; at least bright spiral galaxies are present close to the center of the Coma cluster. We also examine the morphology-density relation for the Coma cluster including its surrounding regions.