Heating Hot Atmospheres with Active Galactic Nuclei

TL;DR

This paper discusses how active galactic nuclei (AGN) inject energy into galaxy cluster atmospheres, preventing cooling and star formation, and explores the mechanisms and implications of this feedback process.

Contribution

It provides insights into the energy transfer from AGN to hot gas in galaxy clusters and examines the role of feedback in galaxy evolution.

Findings

Radio jet powers match energy needed to offset cooling

AGN outbursts require substantial black hole growth

Heating mechanisms influence large-scale cluster properties

Abstract

High resolution X-ray spectroscopy of the hot gas in galaxy clusters has shown that the gas is not cooling to low temperatures at the predicted rates of hundreds to thousands of solar masses per year. X-ray images have revealed giant cavities and shock fronts in the hot gas that provide a direct and relatively reliable means of measuring the energy injected into hot atmospheres by active galactic nuclei (AGN). Average radio jet powers are near those required to offset radiative losses and to suppress cooling in isolated giant elliptical galaxies, and in larger systems up to the richest galaxy clusters. This coincidence suggests that heating and cooling are coupled by feedback, which suppresses star formation and the growth of luminous galaxies. How jet energy is converted to heat and the degree to which other heating mechanisms are contributing, eg. thermal conduction, are not well understood. Outburst energies require substantial late growth of supermassive black holes. Unless all of the approximately 10E62 erg required to suppress star formation is deposited in the cooling regions of clusters, AGN outbursts must alter large-scale properties of the intracluster medium.