Regulation of thermal conductivity in hot galaxy clusters by MHD turbulence

TL;DR

This paper proposes that MHD turbulence driven by heat flux instability regulates thermal conduction in galaxy clusters, helping to stabilize cooling cores through turbulent mixing and magnetic field effects, supported by observed metal distributions.

Contribution

It introduces a model where MHD turbulence driven by heat flux instability controls thermal conduction and stabilizes cooling cores in galaxy clusters, a novel mechanism in cooling flow theory.

Findings

Turbulent mixing correlates with thermal gradients in cooling flows.

Metal distribution in cluster centers supports the model.

Magnetic field effects influence thermal conduction regulation.

Abstract

The role of thermal conduction in regulating the thermal behavior of cooling flows in galaxy clusters is reexamined. Recent investigations have shown that the anisotropic Coulomb heat flux caused by a magnetic field in a dilute plasma drives a dynamical instability. A long standing problem of cooling flow theory has been to understand how thermal conduction can offset radiative core losses without completely preventing them. In this Letter we propose that magnetohydrodynamic turbulence driven by the heat flux instability regulates field-line insulation and drives a reverse convective thermal flux, both of which may mediate the stabilization of the cooling cores of hot clusters. This model suggests that turbulent mixing should accompany strong thermal gradients in cooling flows. This prediction seems to be supported by the spatial distribution of metals in the central galaxies of clusters, which shows a much stronger correlation with the ambient hot gas temperature gradient than with the parent stellar population.