The ESO Nearby Abell Cluster Survey: Kinematics of Galaxies in Clusters

Abstract

We summarize several results based on the velocity data-set for cluster galaxies provided by ENACS (the ESO Nearby Abell Cluster Survey). We describe the distribution of velocity dispersions of a complete sample of rich galaxy clusters, and compare it to the distribution of cluster X-ray temperatures, and with predictions of theoretical models. We then address the issue of the existence of a Fundamental Plane (FP) for rich clusters, first suggested by Schaeffer et al. We confirm the existence of this FP with the ENACS data-set. The cluster FP is different from the FP of elliptical galaxies, and from the virial prediction. Some implications of the cluster FP are discussed. Finally, we describe the phase-space distributions of different populations of cluster galaxies. Different galaxy classes are defined according to their morphological or spectral type, and the presence of emission-lines. Star-forming (late-type) galaxies have a velocity dispersion profile that (in combination with their wider spatial distribution) is suggestive of first infall into the cluster. On the contrary, quiescent (early-type) galaxies show evidence of a dynamically relaxed distribution.