| Two clusters of galaxies with radio-quiet cooling cores (2005) | |||||||||||||||
Abstract | |||||||||||||||
| Two Clusters Galaxies with Radio Quiet Cooling Cores Megan Donahue and Mark Voit Michigan State University Physics Astronomy Dept East Lansing donahue msu edu voit msu edu arXiv astro Aug Christopher Dea Dept Physics Rochester Institute Technology Lomb Memorial Rochester Stefi Baum Center for Imaging Science Rochester Institute Technology Lomb Memorial Rochester William Sparks Space Telescope Science Institute San Martin Baltimore ABSTRACT Radio lobes inflated active galactic nuclei the centers clusters are promising candidate for halting condensation clusters with short central cooling times because they are common such clusters order test the AGNheating hypothesis obtained Chandra observations two clusters with short central cooling times yet evidence for AGN activity Abell and Abell The cores these clusters indeed appear systematically different from cores with more prominent radio emission They not have significant central temperature gradients and their central entropy levels are markedly higher than clusters with stronger radio emission corresponding central cooling times Gyr Also there evidence for fossil ray cavities produced earlier episode AGN heating suggest that either the central gas has not yet cooled the point which feedback necessary prevent from condensing possibly because conductively stabilized the gas experienced major heating event Gyr the past and has not required feedback since then The fact that these clusters with evident feedback have higher central . Radio lobes inflated by active galactic nuclei at the centers of clusters are a promising candidate for halting condensation in clusters with short central cooling times because they are common in such clusters. In order to test the AGNheating hypothesis, we obtained Chandra observations of two clusters with short central cooling times yet no evidence for AGN activity: Abell 1650 and Abell 2244. The cores of these clusters indeed appear systematically different from cores with more prominent radio emission. They do not have significant central temperature gradients, and their central entropy levels are markedly higher than in clusters with stronger radio emission, corresponding to central cooling times ~ 1 Gyr. Also, there is no evidence for fossil X-ray cavities produced by an earlier episode of AGN heating. We suggest that either (1) the central gas has not yet cooled to the point at which feedback is necessary to prevent it from condensing, possibly because it is conductively stabilized, or (2) the gas experienced a major heating event & >~ Gyr in the past and has not required feedback since then. The fact that these clusters with no evident feedback have higher central entropy and therefore longer central cooling times than clusters with obvious AGN feedback strongly suggests that AGNs supply the feedback necessary to suppress condensation in clusters with short central cooling times (Refer to PDF file for exact formulas).. Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Numbers SAO GO3-4159X and AR3-4017A issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. | |||||||||||||||
Details der Publikation | |||||||||||||||
| |||||||||||||||