The Launching of Cold Clouds by Galaxy Outflows. V. The Role of Anisotropic Thermal Conduction

Abstract

Motivated by observations of multiphase galaxy outflows, we explore the impact of isotropic and anisotropic electron thermal conduction on the evolution of radiatively cooled, cold clouds embedded in hot, magnetized winds. Using the adaptive-mesh refinement code AthenaPK , we conduct simulations of clouds impacted by supersonic and transonic flows with magnetic fields initially aligned parallel and perpendicular to the flow direction. In cases with isotropic thermal conduction, an evaporative wind forms, stabilizing against instabilities and leading to a mass-loss rate that matches the hydrodynamic case. In anisotropic cases, the impact of conduction is more limited and strongly dependent on the field orientation. In runs with initially perpendicular fields, the field lines are folded back into the tail, strongly limiting conduction, but magnetic fields act to dampen instabilities and slow the stretching of the cloud in the flow direction. In the parallel case, anisotropic conduction aids cloud survival by forming a radiative wind near the front of the cloud, which suppresses instabilities and reduces mass loss. In all cases, anisotropic conduction has a minimal impact on the acceleration of the cloud.

Keywords

• Circumgalactic medium