The powerful outburst in Hercules A

P. E. J. Nulsen; D. C. Hambrick; B. R. McNamara; D. Rafferty; L. Birzan; M. W. Wise; L. P. David

doi:10.1086/430945

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The powerful outburst in Hercules A

P. E. J. Nulsen·D. C. Hambrick·B. R. McNamara·D. Rafferty·L. Birzan·M. W. Wise·L. P. David

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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.

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P. E. J. Nulsen, D. C. Hambrick, B. R. McNamara, D. Rafferty, L. Birzan, M. W. Wise, L. P. David. 2005-04-15. The powerful outburst in Hercules A. https://doi.org/10.1086/430945

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