A powerful AGN outburst in RBS 797
Number of pages
Faculty of Science (FNWI)
Anton Pannekoek Institute for Astronomy (API)
Utilizing ~50 ks of Chandra X-Ray Observatory imaging, we present an analysis of the intracluster medium (ICM) and cavity
system in the galaxy cluster RBS 797. In addition to the two previously known cavities in the cluster core, the new and deeper
X-ray image has revealed additional structure associated with the active galactic nucleus (AGN). The surface brightness decrements
of the two cavities are unusually large and are consistent with elongated cavities lying close to our line of sight. We estimate
a total AGN outburst energy and mean jet power of (3-6) × 1060 erg and (3-6) × 1045 erg s-1, respectively, depending on the
assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently among the most powerful AGN outbursts known
in a cluster. The average mass accretion rate needed to power the AGN by accretion alone is ~1 M ☉ yr-1. We show that accretion
of cold gas onto the AGN at this level is plausible, but that Bondi accretion of the hot atmosphere is probably not. The brightest
cluster galaxy (BCG) harbors an unresolved, non-thermal nuclear X-ray source with a bolometric luminosity of 2 × 1044 erg
s-1. The nuclear emission is probably associated with a rapidly accreting, radiatively inefficient accretion flow. We present
tentative evidence that star formation in the BCG is being triggered by the radio jets and suggest that the cavities may be
driving weak shocks (M ~ 1.5) into the ICM, similar to the process in the galaxy cluster MS 0735.6+7421.
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