Stars quenching stars: how photoionization by local sources regulates gas cooling and galaxy formation

TL;DR

This paper proposes that photoionization from local star formation sources can significantly delay gas cooling and regulate star formation in galaxies, potentially replacing the need for other feedback mechanisms.

Contribution

It introduces a physically constrained mechanism where local photoionization suppresses gas cooling, affecting galaxy formation models.

Findings

Photoionization removes key coolants from halo gas.

Gas cooling and accretion times increase by 10-100 times.

A critical SFR exists that halts cold mode accretion.

Abstract

Current models of galaxy formation lack an efficient and physically constrained mechanism to regulate star formation (SF) in low and intermediate mass galaxies. We argue that the missing ingredient could be the effect of photoionization by local sources on the gas cooling. We show that the soft X-ray and EUV flux generated by SF is able to efficiently remove the main coolants (e.g., HeII, OV and FeIX) from the halo gas via direct photoionization. As a consequence, the cooling and accretion time of the gas surrounding star-forming galaxies may increase by one or two orders of magnitude. For a given halo mass and redshift, the effect is directly related to the value of the star formation rate (SFR). Our results suggest the existence of a critical SFR above which "cold" mode accretion is stopped, even for haloes with virial masses well below the critical shock-heating mass suggested by previous studies.The evolution of the critical SFR with redshift, for a given halo mass, resembles the respective steep evolution of the observed SFR for z<1. This suggests that photoionization by local sources would be able to regulate gas accretion and star formation, without the need for additional, strong feedback processes.