A Kinematic Search for Bound Populations around Brightest Cluster Members in a Sample of 52 Clusters of Galaxies

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Abstract
We measured the radial velocities of 265 galaxies in the field of 52 clusters in the redshift range 0.05 < z < 0.25. In a 93% complete sample of galaxies close to the brightest cluster members (BCMs; d < 40 kpc) we found that the percentage (43 ± 9%) of galaxies with |dV| < 300 km s-1 is higher than the one (28 ± 4%) of a control sample of more distant galaxies. Moreover, we found that the velocity dispersion (576 km s-1) of the galaxies in the inner sample is lower than the one (866 km s-1) of the control sample. The sample's velocity dispersion is also lower than the expectation from the fit of the velocity dispersion profile of all data combined in a pseudocluster with dynamical models of the cluster mass distribution. We discuss these results in the light of the existence of a bound population of galaxies that will eventually merge with the BCM as a general feature of clusters of galaxies.