Thermal diffusion in the IGM of clusters of galaxies

Abstract

We revisit the phenomenon of elements diffusion in the intergalactic medium (IGM) in clusters of galaxies. The diffusion is driven by gravity, concentration and temperature gradients. The latter cause thermal diffusion, which has been so far ignored in IGM studies. We consider the full problem based on the Burgers' equations and demonstrate that the temperature gradients present in clusters of galaxies may successfully compete with gravity, evacuating metals from cooler regions. Under the combined action of gravity and temperature gradients, complicated metallicity profiles with several peaks and depressions may be formed. For a typical cool core cluster, the thermal diffusion may significantly reduce and even reverse the gravitational sedimentation of metals, resulting in the depression in their abundance in the core. This may have implications for diagnostics of the low temperature plasma in the centers of clusters of galaxies.