AGN feedback and its quenching efficiency

TL;DR

This paper reviews recent observations of gas outflows driven by AGN, discussing their role in suppressing star formation and the complexities of measuring their overall quenching effectiveness.

Contribution

It provides a comprehensive discussion of AGN feedback mechanisms, especially the quenching efficiency, based on recent observational data and case studies.

Findings

AGN-driven outflows have mass outflow rates 1-5 times the star formation rate

Radio jets can effectively suppress star formation in certain galaxy environments

The net impact of AGN feedback on star formation can be both positive and negative

Abstract

In the last decade, observations have accumulated on gas outflows in galaxies, and in particular massive molecular ones. The mass outflow rate is estimated between 1-5 times the star formation rate. For the highest maximal velocities, they are driven by AGN; these outflows are therefore a clear way to moderate or suppress star formation. Some of the most convincing examples at low redshift come from the radio mode, when the radio jets are inclined towards the galaxy plane, or expand in the hot intra-cluster medium, in cool core clusters. However, AGN feedback can also be positive in many occasions, and the net effect is difficult to evaluate. The quenching efficiency is discussed in view of recent observations.