Stabilization of systems of galaxies by subclustering

We investigate the contribution of gravitationally bound subsystems to the potential energy of systems of galaxies. We derive a statistical correction factor to the virial mass using Holmberg's observed frequency function of multiple galaxies. It is of the order of ten for groups of galaxies and negligible for rich clusters. However, we emphasize that an individual treatment is necessary. As an illustration we calculate the contribution to the binding energy by observed binary galaxies in the de Vaucouleurs groups 48 and 49, and the Coma Cluster. In all three cases a single double galaxy removes the virial mass paradox. We conclude that corrections for subclustering are substantial in stability analyses of systems of galaxies, that they can remove easily mass discrepancies of the order of ten in groups and rich clusters, and that they should be made individually and not statistically.