GALAXY CLUSTERS IN THE SWIFT /BURST ALERT TELESCOPE ERA: HARD X-RAYS IN THE INTRACLUSTER MEDIUM

• Main Authors: Ajello, M. (Author), Rebusco, Paola (Contributor), Cappelluti, N. (Author), Reimer, O. (Author), Böhringer, H. (Author), Greiner, J. (Author), Gehrels, N. (Author), Tueller, J. (Author), Moretti, A. (Author)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor)
• Format: Article
• Language: English
• Published: Institute of Physics/American Astronomical Society, 2015-03-06T20:03:29Z.
• Subjects: Article
• Online Access: Get fulltext

We report the detection of 10 clusters of galaxies in the ongoing Swift/Burst Alert Telescope (BAT) all-sky survey. This sample, which mostly comprises merging clusters, was serendipitously detected in the 15-55 keV band. We use the BAT sample to investigate the presence of excess hard X-rays above the thermal emission. The BAT clusters do not show significant (e.g., ≥2σ) nonthermal hard X-ray emission. The only exception is represented by Perseus whose high-energy emission is likely due to NGC 1275. Using XMM-Newton, Swift/XRT, Chandra and BAT data, we are able to produce upper limits of the inverse Compton (IC) emission mechanism which are in disagreement with most of the previously-claimed hard X-ray excesses. The coupling of the X-ray upper limits of the IC mechanism to radio data shows that, in some clusters, the magnetic field might be larger than 0.5 μG. We also derive the first log N-log S and luminosity function distributions of galaxy clusters above 15 keV.
United States. National Aeronautics and Space Administration (NASA grant NNX07AV03G)
Deutsche Forschungsgemeinschaft (DFG Leibniz-Prize (HA 1850/28-1))
Massachusetts Institute of Technology (Pappalardo Postdoctoral Fellowship in Physics)