Galaxy clusters in the swift/burst alert telescope era: Hard X-rays in the intracluster medium

M. Ajello, P. Rebusco, N. Cappelluti, O. Reimer, H. Böhringer, J. Greiner, N. Gehrels, J. Tueller, A. Moretti

Research output: Contribution to journalArticlepeer-review

83 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)367-388
Number of pages22
JournalAstrophysical Journal
Issue number1
StatePublished - 2009
Externally publishedYes


  • Acceleration of particles
  • Galaxies: clusters: general
  • Magnetic fields
  • Radiation mechanisms: non-thermal
  • X-rays: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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