Radial Density and Temperature Profiles of the Intracluster Gas Constructed Jointly from the X‐Ray Surface Brightness Measurement and the Universal Density Profile

In this paper we have made an attempt to derive the radial profiles ofdensity and temperature of intracluster gas based on the two well-establishedfacts at present: the X-ray observed surface brightness of clusters describedby the standard beta model and the (NFW) universal density profile as theunderlying dark matter distribution. We have numerically solved the hydrostaticequation by demanding that the volumed-averaged baryon fraction of a clustershould asymptotically approach the universal value at its viral radius. We haveshown that the radial temperature variation derived from these constraintsdiffers significantly from the conventional polytropic equation of state: Thegas temperature profile may show a dramatic increase or decrease with outwardradius, depending sensitively on the beta parameter. A large beta value(typically greater than 0.8) is required in order to ensure that the X-raytemperature makes a drop at the virial radius. This indicates that either theNFW profile is inappropriate to apply for the overall dark matter distributionof clusters or other non-gravitational heating processes may play an importantrole in the dynamical evolution of clusters.Comment: 26 pages, 4 figures, accepted for publication in Ap