AGN heating and ICM cooling in the HIFLUGCS sample of galaxy 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, LR, defined as the total synchrotron power between 10 MHz and 15 GHz. We adopt the central cooling time, tcool, as the diagnostic to ascertain cooling properties of the clusters and classify clusters with tcool < 1 Gyr as strong cooling core (SCC) clusters, with 1 Gyr < tcool <7.7 Gyr as weak cooling core (WCC) clusters and with tcool > 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-171 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 LR 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 LR 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, LBCG, with LR and cluster parameters. We invoke the relation between LBCG and the black hole mass, MBH, and find a surprisingly tight correlation between MBH and LR for SCC clusters. We find also an excellent correlation of LBCG with M500 and LX 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]