Models of Galaxy Clusters with Thermal Conduction

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Abstract
We present a simple model of hot gas in galaxy clusters, assuming hydrostatic equilibrium and energy balance between radiative cooling and thermal conduction. For five clusters, A1795, A1835, A2199, A2390, and RX J1347.5-1145, the model gives a good description of the observed radial profiles of electron density and temperature, provided that we take the thermal conductivity κ to be about 30% of the Spitzer conductivity. Since the required κ is consistent with the recent theoretical estimate of Narayan & Medvedev for a turbulent magnetized plasma, we consider a conduction-based equilibrium model to be viable for these clusters. We further show that the hot gas is thermally stable because of the presence of conduction. For five other clusters, A2052, A2597, Hydra A, Ser 159-03, and 3C 295, the model requires unphysically large values of κ to fit the data. These clusters must have some additional source of heat, possibly an active galactic nucleus, since all the clusters have strong radio galaxies at their centers. We suggest that thermal conduction, although not dominant in these clusters, may nevertheless play a significant role by preventing the gas from becoming thermally unstable.