Substructure in the ENACS clusters

Subclustering is investigated in a set of 67 rich cluster galaxy samples ex tracted from the ESO Nearby Abell Cluster survey (ENACS) catalog. We apply four well-known statistical techniques to evaluate the frequency with which substructure occurs. These diagnostics are sensitive to different aspects of the spatial and velocity distribution of galaxies and explore different scales, thus providing complementary tests of subclustering. The skewness a nd kurtosis of the global radial velocity distributions, useful for judging the normality, and the powerful a test of Dressier & Shectman, which measu res local deviations from the global kinematics, show that the ENACS cluste rs exhibit a degree of clumpiness in reasonable agreement with that found i n other less homogeneous and smaller cluster datasets. On the other hand, t he average two-point correlation function of the projected galaxy distribut ions reveals that only similar to 10% of the systems investigated show evid ence for substructure at scale lengths smaller than 0.2 h(-1) Mpc. This is much less than in earlier studies based on the Dressier & Shectman's cluste r sample. We find indications of a possible systematic deficiency of galaxi es at small intergalactic separations in the ENACS clusters.