Anisotropic Thermal Conduction and the Cooling Flow Problem in Galaxy Clusters

Ian Parrish
UC Berkeley Astronomy Department


We examine the long-standing cooling flow problem in galaxy clusters with 3D MHD simulations including radiative cooling and anistropic thermal conduction along magnetic field lines. The central regions of the intracluster medium (ICM) can have cooling times as short as 100 Myr. In order to prevent a cooling catastrophe, the ICM must be heated by some mechanism, such as AGN feedback or thermal conduction from the thermal reservoir at large radii. The cores of galaxy clusters are unstable to the heat-flux-driven buoyancy instability (HBI), a convective instability. We find that the HBI rearranges the magnetic field lines to be preferentially perpendicular to the temperature gradient, suppressing the effective radial thermal conductivity to less than 10% of the Spitzer value. For cool core, low central entropy clusters, we find that thermal conduction alone cannot prevent a cooling catastrophe. For non cool core, high central entropy clusters, we find that thermal conduction can provide sufficient heating for cosmologically interesting timescales. Finally, we briefly mention where we are going for studying AGN feedback and buoyant bubbles.