The distribution of dark matter in the coma cluster

Abstract

Limitations on positional and kinematical data for the distribution of dark matter in the Coma cluster are shown to cast doubt on any assumption of a constant M/L ratio. Attention is given to the possible forms of a smooth, spherical background potential (BP) for which positive phase space distribution functions that agree with available positions and radial velocities. Virial theorem, as applied to clusters of galaxies, assumes that galaxies and dark matter have similar distributions. The theorem can be used, together with complete velocity profiles calculated from velocity dispersion data, to constrain the distribution of dark matter. The constant M/L ratio then could be valid for the Coma cluster, provided subclustering or asymmetries in the galaxy distribution are negligible. 28 references.