On the kinematical behavior of galaxies in clusters

Abstract

We have analyzed the sample of 15 galaxy clusters published by Dressler and Shectman (1988a) to search for a trend for spiral and irregular galaxies to have greater velocity dispersion than the ellipticals and lenticulars. We have shown that this trend is highly significant, with a probability of less than 0.05% that it may result from statistical fluctuations in our sample of clusters. An analogous but much less significant effect appears also to be present between lenticular and elliptical galaxies. We interpret these results as evidence that late-type galaxies are still in the process of infalling towards the virialized cluster cores.