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The Curious Case of Abell 2256

By Tracy E. Clarke, Torsten Enßlin, Alexis Finoguenov, Huib Intema, Christoph Pfrommer, Reinout van Weeren, Huub Röttgering and Raymond Oonk


Abell 2256 is a rich, nearby (z=0.0594) galaxy cluster that has significant evidence of merger activity. We present new radio and X-ray observations of this system. The low-frequency radio images trace the diffuse synchrotron emission of the Mpc-scale radio halo and relics as well as a number of recently discovered, more compact, steep spectrum sources. The spectral index across the relics steepens from the north-west toward the south-east. Analysis of the spectral index gradients between low and and high-frequencies shows spectral differences away from the north-west relic edge such that the low-frequency index is significantly flatter than the high frequency spectral index near the cluster core. This trend would be consistent with an outgoing merger shock as the origin of the relic emission. New X-ray data from XMM-Newton reveal interesting structures in the intracluster medium pressure, entropy and temperature maps. The pressure maps show an overall low pressure core co-incident with the radio halo emission, while the temperature maps reveal multiple regions of cool emission within the central regions of Abell 2256. The two cold fronts in Abell 2256 both appear to have motion in similar directions.Comment: 4 pages, 3 figures, proceedings of contributed talk at "Non-Thermal Phenomena in Colliding Galaxy Clusters", held in Nice, 15-18 November 2010. To be published in Mem. S.A.I

Topics: Astrophysics - Cosmology and Nongalactic Astrophysics
Year: 2011
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