The Mass of the Coma Cluster: Combined X-Ray and Optical Results

The mass of the Coma Cluster of galaxies has been determined from X-ray data using a general technique which allows for direct comparison with optical results. The preferred model for both sets of data is one in which the mass distribution follows the distribution of the optical light. The total virial mass within 5h_50_^-1^ Mpc is (1.85 + 0.24) x 10^15^h_50_^-1^ M_sun_, and the mass-to-light ratio is 165 +/- 25h_50_ in solar units. A large class of more general dark matter distributions was also found to be consistent with the data. For these models the range in total mass is larger (1.1-3.0) x 10^15^h_50_^-1^ M_sun_, and-the mass-to-light ratio varies from 90h_50_ to 250h_50_. The ratio of virial mass to X-ray emitting gas mass seems to decrease with radius from the cluster center. The presently available X-ray data have significantly restricted the optically allowed distributions for the virial mass.