Temperature Profiles of Nearby Clusters of Galaxies

Abstract

We report results from the analysis of 21 nearby galaxy clusters, 11 with cooling flow (CF) and 10 without cooling flow, observed with BeppoSAX. The temperature profiles of both CF and non-CF systems are characterized by an isothermal core extending out to 0.2 r_180; beyond this radius both CF and non-CF cluster profiles rapidly decline. Our results differ from those derived by other authors who either found continuously declining profiles or substantially flat profiles. Neither the CF nor the non-CF profiles can be modeled by a polytropic temperature profile, the reason being that the radius at which the profiles break is much larger than the core radius characterizing the gas density profiles. For r > 0.2 r_180, where the gas can be treated as a polytrope, the polytropic indices derived for CF and non-CF systems are respectively 1.20 +/- 0.06 and 1.46 +/- 0.06. The former index is closer to the isothermal value, 1, and the latter to the adiabatic value, 5/3. Published hydrodynamic simulations do not reproduce the peculiar shape of the observed temperature profile, probably suggesting that a fundamental ingredient is missing.