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130 - K. W. Cavagnolo 2011
Utilizing $sim 50$ 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 dee per 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 $approx 3 - 6 times 10^{60}$ erg and $approx 3 - 6 times 10^{45}$ erg s$^{-1}$, respectively, depending on the assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently among the the most powerful AGN outbursts known in a cluster. The average mass accretion rate needed to power the AGN by accretion alone is $sim 1 M_{odot}$ 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 BCG harbors an unresolved, non-thermal nuclear X-ray source with a bolometric luminosity of $approx 2 times 10^{44}$ 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 ($M sim 1.5$) into the ICM, similar to the process in the galaxy cluster MS 0735.6+7421.
112 - K. W. Cavagnolo 2010
Using Chandra X-ray and VLA radio data, we investigate the scaling relationship between jet power, P_jet, and synchrotron luminosity, P_rad. We expand the sample presented in Birzan et al. (2008) to lower radio power by incorporating measurements for 21 gEs to determine if the Birzan et al. (2008) P_jet-P_rad scaling relations are continuous in form and scatter from giant elliptical galaxies (gEs) up to brightest cluster galaxies (BCGs). We find a mean scaling relation of P_jet approximately 5.8x10^43 (P_rad/10^40)^(0.70) erg/s which is continuous over ~6-8 decades in P_jet and P_rad with a scatter of approximately 0.7 dex. Our mean scaling relationship is consistent with the model presented in Willott et al. (1999) if the typical fraction of lobe energy in non-radiating particles to that in relativistic electrons is > 100. We identify several gEs whose radio luminosities are unusually large for their jet powers and have radio sources which extend well beyond the densest parts of their X-ray halos. We suggest that these radio sources are unusually luminous because they were unable to entrain appreciable amounts of gas.
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