Nonpolytropic Model for the Coma Cluster

In this article we demonstrate, for the first time, how a physically motivated static model for both the gas and galaxies in the Coma Cluster of galaxies can jointly fit all available X-ray and optical imaging and spectroscopic data. The principal assumption of this nonpolytropic model (Cavaliere & Fusco-Femiano 1981, hereafter CFF), is that the intracluster gas temperature is proportional to the square of the galaxy velocity dispersion everywhere throughout the cluster; no other assumption about the gas temperature distribution is required. After demonstrating that the CFF nonpolytropic model is an adequate representation of the gas and galaxy distributions, the radial velocity dispersion profile, and the gas temperature distribution, we derive the following information about the Coma Cluster: 1. The central temperature is about 9 keV and the central density is 2.8 x 10^-3^ cm^-3^ for the X-ray emitting plasma; 2. The binding mass of the cluster is approximately 2 x 10^15^ M_sun_ within 5 Mpc (for H_0_ = 50 km s^-1^ Mpc^-1^), with a mass-to-light ratio of ~160 M_sun_/L_sun_; 3. The contribution of the gas to the total virial mass increases with distance from the cluster center, and we estimate that this ratio is no greater than ~50% within 5 Mpc. The ability of the CFF nonpolytropic model to describe the current X- ray and optical data for the Coma Cluster suggests that a significant fraction of the thermal energy contained in the hot gas in this as well as other rich galaxy clusters may have come from the interaction between the galaxies and the ambient cluster medium.