DYNAMICS OF THE MICROWAVE-DECREMENT CLUSTER ABELL-665

We have measured the radial velocities of 41 galaxies in the field of Abell 665, the richest cluster in the Abell catalog and one of only three clusters for which detection of a microwave decrement is well established. Thirty-three of the 41 galaxies observed are determined to be cluster members. The distribution of velocities is well fitted by a Gaussian indicating that the cluster is not a superposition of groups or clusters at significantly different velocities. Nevertheless, based on the positions of a larger sample of galaxies, we find that subclustering is likely to be present. The mean observed redshift of A665 is 0.18144 +/- 0.00084, and the velocity dispersion is 1201(-126)+183 km s-1, in rough agreement with predictions from recent models of the microwave decrement and X-ray-emitting intracluster gas. The brightest cluster member (BCM) has a velocity which is 447 km s-1 larger than our sample's median velocity. The hypothesis that the median cluster velocity could be as large as the velocity of the BCM can be ruled out at the 98% confidence level. This large peculiar velocity may be indicative of velocity subclustering which is not apparent in the observed sample of 33 velocities.