CLUSTERS OF GALAXIES ASSOCIATED WITH QUASARS .2. GALAXY CLUSTER DYNAMICS

Multiobject spectroscopy of galaxies associated with optically luminous quasars with 0.15 < Z < 0.6 is presented. The relative radial velocities of galaxies within 500 kpc of the quasars seem to be well described by a Gaussian distribution with a dispersion of 400-500 km s-1. This result is independent of whether the quasar is radio-loud or radio-quiet, and, more surprisingly, whether it is located in a rich cluster of galaxies or in a poor group. Comparison with galaxy cluster dynamics for different environments indicates that the rich clusters of galaxies associated with quasars have anomalously low velocity dispersions, whereas the poor groups of galaxies may be dynamically normal. This result is consistent with models of quasar formation triggered by galaxy-galaxy interaction, where the efficiency of such interactions is much greater for low relative velocities.