Intergalactic Filaments as Isothermal Gas Cylinders

TL;DR

This study uses cosmological simulations to show that intergalactic filaments often form isothermal gas cylinders with specific density and temperature profiles, influencing galaxy gas accretion processes.

Contribution

It demonstrates that hydrodynamic gas properties, rather than dark matter, primarily determine the formation of isothermal gas cylinders in intergalactic filaments.

Findings

Gas density in filaments is about 500 times the cosmic mean.

Gas temperature is typically 10,000-20,000 K, just above the Lyman alpha cooling floor.

The total mass per unit length of these cylinders is determined by temperature and ionization state.

Abstract

Using a cosmological simulation at redshift 5, we find that the baryon-rich cores of intergalactic filaments extending outward from galaxies commonly form isothermal gas cylinders in regions favorable to their formation. The central gas density is typically about 500 times the cosmic mean total density, and the temperature is typically 1-2 times 10^4 K, just above the Lyman alpha cooling floor. These findings argue that the hydrodynamic properties of the gas are more important than the dark matter in determining this structure. It is noteworthy that the temperature and ionization state of the gas completely determine a finite total mass per unit length of an isothermal cylinder. Our findings may have implications for understanding the "cold mode" mechanism of gas transport into galaxies.