THE ASTRONOMICAL JOURNAL      VOLUME 104, NUMBER 6, PAGE 2078     DECEMBER 1992

    STRUCTURE, ROTATION, AND THE PECULIAR VELOCITY cD GALAXY IN ABELL 2107

                              WILLIAM R. OEGERLE

     Space Telescope Science Institute, 3700 San Martin Drive, Baltimore,
                                Maryland 21218

                                 JOHN M. HILL

       Steward Observatory, University of Arizona, Tucson, Arizona 85721

                                   ABSTRACT

    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 A2105 is 12335 +/- 86 km/s and
    the velocity dispersion is 672 [+67,-52] km/s.  The cD galaxy has a
    peculiar velocity of 270 km/s 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.