Redshifts and morphology of galaxies in the Coma cluster

Abstract

Using new observations of redshift and morphology, a sample of galaxies brighter than a radio magnitude of 15.8 is nearly completed to a radial distance of 2.79 deg from the center of the Coma cluster. The redshift results show that the line-of-sight velocity dispersion first decreases and then increases again with distance from the cluster center with a mean value of 896 km/s. A marginally positive test for solid-body rotation of 85 plus or minus 66 km/s per degree is also found. These results are consistent with numerical models of partially relaxed systems. The morphological study shows that the relative number of spiral and irregular galaxies increases with radial distance. This seems consistent with the existence of a hot intracluster medium, although an alternative view cannot be excluded at this time that the elliptical and spiral galaxies form independent systems.