Thermal instability in the collisionally cooled gas

Abstract

We have presented the non-equilibrium (time-dependent) cooling rate and ionization state calculations for a gas behind shock waves with $v\sim 50-150$ km s${}^{-1}$ ($T_s\sim 0.5-6\times 10^5$ K). Such shock waves do not lead to the radiative precursor formation, i.e. the thermal evolution of a gas behind the shock waves are controlled by collisions only. We have found that the cooling rate in a gas behind the shock waves with $v\sim 50-120$ km s${}^{-1}$ ($T_s\sim 0.5-3\times 10^5$ K) differs considerably from the cooling rate for a gas cooled from $T=10^8$ K. It is well-known that a gas cooled from $T=10^8$ K is thermally unstable for isobaric and isochoric perturbations at $T \simgt 2\times 10^4$ K. We have studied the thermal instability in a collisionally controlled gas for shock waves with $v\sim 50-150$ km s${}^{-1}$. We have found that the temperature range, where the postshock gas is thermally unstable, is significantly modified and depends on both gas metallicity and ionic composition of a gas before shock wave. For $Z \simgt 0.1Z_\odot$ the temperature range, where the thermal instability criterion for isochoric perturbations is not fulfilled, widens in comparison with that for a gas cooled from $T=10^8$ K, while that for isobaric perturbations remains almost without a change. For $Z\sim Z_{\odot }$ a gas behind shock waves with $v \simlt 65$ km s${}^{-1}$ ($T_s \simlt 10^5$ K) is thermally stable to isochoric perturbations during full its evolution. We have shown that the transition from isobaric to isochoric cooling for a gas with $Z \simgt 0.1Z_\odot$ behind shock waves with $T_s=0.5-3\times 10^5$ K proceeds at lower column density layer behind a shock wave than that for a gas cooled from $T=10^8$ K. (abridged)

8 pages, 10 figures, accepted to MNRAS

References in corpus (5)

• Time-Dependent Ionization in Radiatively Cooling Gas
• Metal Cooling in Simulations of Cosmic Structure Formation
• Nonequilibrium ionization states and cooling rates of the photoionized enriched gas
• Spectral shape of the UV ionizing background and HeII absorption at redshifts 1.8 < z < 2.9
• Carbon ionization states and the cosmic far-UV background with HeII absorption

Cited by in corpus (5)

• Non-equilibrium cooling rate for a collisionally cooled metal-enriched gas
• Evolution of multiple supernova remnants
• Dynamics of a Supernova Envelope in a Cloudy Interstellar Medium
• Modeling of Spiral Structure in a Multi-Component Milky~Way-Like Galaxy
• Relativistic Thermal Emission from Accretion Disks in Kerr-MOG Spacetimes