On the prevalence of radio-loud active galactic nuclei in brightest cluster galaxies: implications for AGN heating of cooling flows 论文

摘要

The prevalence of radio-loud active galactic nucleus (AGN) activity in present-day massive haloes is determined using a sample of 625 nearby groups and clusters selected from the Sloan Digital Sky Survey. Brightest group and cluster galaxies (BCGs) are more likely to host a radioloud AGN than other galaxies of the same stellar mass (by below a factor of 2 at a stellar mass of 5 10 11 M , but rising to over an order of magnitude below 10 11 M ). The distribution of radio luminosities for BCGs does not depend on mass, however, and is similar to that of field galaxies of the same stellar mass. Neither the radio-loud fraction nor the radio luminosity distribution of BCGs depends strongly on the velocity dispersion of the host cluster. The radio-AGN fraction is also studied as a function of distance from the cluster centre. Only within 0.2r 200 do cluster galaxies exhibit an enhanced likelihood of radio-loud AGN activity, which approaches that of the BCGs. In contrast to the radio properties, the fraction of galaxies with optical emission-line AGN activity is suppressed within r 200 in groups and clusters, decreasing monotonically towards the cluster centre.