The powerful outburst in Hercules A
Abstract
The radio source Hercules A resides at the center of a cooling flow cluster of galaxies at redshift z = 0.154. A Chandra X-ray image reveals a shock front in the intracluster medium (ICM) surrounding the radio source, about 160 kpc from the active galactic nucleus (AGN) that hosts it. The shock has a Mach number of 1.65, making it the strongest of the cluster-scale shocks driven by an AGN outburst found so far. The age of the outburst ~5.9e7 y, its energy about 3e61 erg and its mean power ~1.6e46 erg/s. As for the other large AGN outbursts in cooling flow clusters, this outburst overwhelms radiative losses from the ICM of the Hercules A cluster by a factor of ~100. It adds to the case that AGN outbursts are a significant source of preheating for the ICM. Unless the mechanical efficiency of the AGN in Hercules A exceeds 10%, the central black hole must have grown by more than 1.7e8 Msun to power this one outburst.
Cite
@article{arxiv.astro-ph/0504350,
title = {The powerful outburst in Hercules A},
author = {P. E. J. Nulsen and D. C. Hambrick and B. R. McNamara and D. Rafferty and L. Birzan and M. W. Wise and L. P. David},
journal= {arXiv preprint arXiv:astro-ph/0504350},
year = {2009}
}
Comments
4 pages, 5 figures, accepted by ApJL