The effect of saturated thermal conduction on clouds in a hot plasma by Bastian Sander et al. on Tuesday 29 November

We numerically investigate the internal evolution of multiphase clouds, which

are at rest with respect to an ambient, highly ionized medium (HIM)

representing the hot component of the circumgalactic medium (CGM).

Time-dependent saturated thermal conduction and its implications like

condensation rates and mixing efficiency are assessed in multiphase clouds. Our

simulations are carried out by using the adaptive mesh refinement code Flash.

We perform a grid of models of which we present here those characteristic for

the presented study. The model clouds are initially in both hydrostatic and

thermal equilibrium and are in pressure balance with the HIM. Thus, they have

steep gradients in both temperature and density at the interface to HIM leading

to non-negligible thermal conduction. Several physical processes are considered

numerically or semi-analytically: thermal conduction, radiative cooling and

external heating of gas, self-gravity, mass diffusion, and dissociation of

molecules and ionization of atoms. It turns out that saturated thermal

conduction triggers a continuous condensation irrespective of cloud mass.

Dynamical interactions with ambient HIM all relate to the radial density

gradient in the clouds: (1) mass flux due to condensation is the higher the

more homogeneous the clouds are; (2) mixing of condensed gas with cloud gas is

easier in low-mass clouds, because of their shallower radial density gradient;

thus (3) accreted gas is distributed more efficiently. A distinct and

sub-structured transition zone forms at the interface between cloud and HIM,

which starts at smaller radii and is much narrower as deduced from analytical

theory.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15284v1