AGN heating and ICM cooling in the HIFLUGCS sample of galaxy clusters

TL;DR

This study investigates the relationship between AGN radio luminosity and cooling properties in galaxy clusters, revealing strong correlations and evidence of AGN feedback regulating the cooling process, especially in strong cooling core clusters.

Contribution

It provides new insights into the scaling relations between AGN activity, cluster mass, and cooling properties, highlighting the role of AGN feedback in galaxy cluster evolution.

Findings

Higher radio luminosity in SCC clusters correlates with cluster mass.

Strong correlation between black hole mass and radio luminosity in SCC clusters.

AGN presence is more common in cooling core clusters.

Abstract

We have carried out an intensive study of the AGN heating-ICM cooling network by comparing various cluster parameters of the HIFLUGCS sample to the integrated radio luminosity of the central AGN, L_R, defined as the total synchrotron power between 10 MHz and 15 GHz. We adopt the central cooling time, t_cool, as the diagnostic to ascertain cooling properties of the clusters and classify clusters with t_cool < 1 Gyr as strong cooling core (SCC) clusters, with 1 Gyr < t_cool <7.7 Gyr as weak cooling core (WCC) clusters and with t_cool > 7.7 Gyr as non-cooling core (NCC) clusters. We find 48 out of 64 clusters (75%) contain cluster center radio sources (CCRS) cospatial with or within 50 h^{-1}_{71} kpc of the X-ray peak emission. Further, we find that the probability of finding a CCRS increases from 45% to 67% to 100% for NCC, WCC and SCC clusters, respectively, suggesting an AGN-feedback machinery in SCC clusters which regulates the cooling in the central regions. We find L_R in SCC clusters depends strongly on the cluster scale such that more massive clusters harbor more powerful radio AGN. The same trend is observed between L_R and the classical mass deposition rate, MDR, albeit much stronger, in SCC and partly also in WCC clusters. We also perform correlations of the 2MASS K-band luminosity of the brightest cluster galaxy, L_BCG, with L_R and cluster parameters. We invoke the relation between L_BCG and the black hole mass, M_BH, and find a surprisingly tight correlation between M_BH and L_R for SCC clusters. We find also an excellent correlation of L_BCG with M500 and L_X for the entire sample; however, SCC clusters show a tighter trend in both the cases. We discuss the plausible reasons behind these scaling relations in the context of cooling flows and AGN feedback. [Abridged]