Crushing of interstellar gas clouds in supernova remnants. I. The role of thermal conduction and radiative losses

TL;DR

This study models how shock waves from supernova remnants interact with interstellar gas clouds, highlighting the roles of radiative cooling and thermal conduction in different shock regimes and their effects on cloud evolution.

Contribution

It provides a detailed analysis of the interplay between radiative cooling and thermal conduction in supernova remnant-cloud interactions across different Mach number regimes.

Findings

Radiative losses dominate at lower Mach numbers, leading to cloud fragmentation.

Thermal conduction causes cloud evaporation at higher Mach numbers.

Thermal conduction suppresses hydrodynamic instabilities at cloud boundaries.

Abstract

We model the hydrodynamic interaction of a shock wave of an evolved supernova remnant with a small interstellar gas cloud like the ones observed in the Cygnus loop and in the Vela SNR. We investigate the interplay between radiative cooling and thermal conduction during cloud evolution and their effect on the mass and energy exchange between the cloud and the surrounding medium. Through the study of two cases characterized by different Mach numbers of the primary shock (M = 30 and 50, corresponding to a post-shock temperature $T\approx 1.7\times 10^6$ K and $\approx 4.7\times 10^6$ K, respectively), we explore two very different physical regimes: for M = 30, the radiative losses dominate the evolution of the shocked cloud which fragments into cold, dense, and compact filaments surrounded by a hot corona which is ablated by the thermal conduction; instead, for M = 50, the thermal conduction dominates the evolution of the shocked cloud, which evaporates in a few dynamical time-scales. In both cases we find that the thermal conduction is very effective in suppressing the hydrodynamic instabilities that would develop at the cloud boundaries.