The Cluster of Galaxies Surrounding Cygnus A II: New Velocities and a Dynamical Model

We have spectroscopically identified 77 new members of the Cygnus A cluster, bringing the total to 118 galaxies consistent with cluster membership. We use these data combined with the results from X-rays to deduce a dynamical model for the system. The data are consistent with a cluster-cluster merger viewed at a projection angle of 30-45 degrees, 0.2-0.6 Gyr prior to core passage. We estimate the richness of the combined cluster system at Abell richness class 2 or greater, suggesting the merger of two richness class 1 clusters.