The contribution of non-central radio galaxies to AGN feedback in rich galaxy clusters

TL;DR

This study investigates the role of non-central radio galaxies in heating the intra-cluster medium of galaxy clusters, using radio and X-ray observations to estimate jet powers and their potential impact on cluster cooling.

Contribution

It provides the first detailed estimates of jet powers from non-central radio galaxies in multiple clusters, highlighting their possible significance in cluster heating processes.

Findings

Non-central radio galaxies are detected in 4.5% of galaxies above the survey limit.

Most unresolved radio sources are likely due to star formation, not AGN activity.

Jet powers range from 10^43 to 10^46 erg/s, comparable to central brightest cluster galaxies.

Abstract

We present a combined radio/X-ray study of six massive galaxy clusters, aimed at determining the potential for heating of the intra-cluster medium (ICM) by non-central radio galaxies. Since X-ray cavities associated with the radio lobes of non-central galaxies are generally not detectable, we use Giant Metrewave Radio Telescope 610~MHz observations to identify jet sources and estimate their size, and Chandra data to estimate the pressure of the surrounding ICM. In the radio, we detect 4.5% of galaxies above the spectroscopic survey limit (M*K+2.0) of the Arizona cluster redshift survey (ACReS) which covers five of our six clusters. Approximately one tenth of these are extended radio sources. Using star formation (SF) rates determined from mid-infrared data, we estimate the expected contribution to radio luminosity from the stellar population of each galaxy, and find that most of the unresolved or poorly-resolved radio sources are likely star formation dominated. The relatively low frequency and good spatial resolution of our radio data allows us to trace star formation emission down to galaxies of stellar mass ~10^9.5 Msol. We estimate the enthalpy of the (AGN dominated) jet/lobe and tailed sources, and place limits on the energy available from unresolved radio jets. We find jet powers in the range ~10^43-10^46 erg/s, comparable to those of brightest cluster galaxies. Our results suggest that while cluster-central sources are the dominant factor balancing ICM cooling over the long term, non-central sources may have a significant impact, and that further investigation is possible and warranted.