STRUCTURE, ROTATION, AND THE PECULIAR VELOCITY CD GALAXY IN ABELL-2107

As part of a program to study the kinematics of cD clusters of galaxies, we have measured the radial velocities of 75 galaxies in the field of Abell 2107. Sixty-eight of these galaxies are cluster members. The mean observed velocity of A2107 is 12335+/-86 km s-1 and the velocity dispersion is 672(-52)+67 km s-1. The cD galaxy has a peculiar velocity of 270 km s-1 with respect to the cluster mean. The distribution of velocities is well fitted by a Gaussian, but the velocities are spatially correlated. We have investigated simple two-body subcluster models for A2107, which are consistent with the observed data and account for the peculiar velocity of the cD galaxy. Alternatively, the spatial distribution of velocities is also consistent with rotation of a single cluster at the 98% confidence level. However, the pure rotation model fails to explain the peculiar velocity of the cD galaxy, which lies at the center of the cluster.