Schedule Mar 18, 2011
Multi-frequency Radio and X-ray Study of the Merging Cluster Abell 2256
Tracy Clarke (NRL)

Cluster mergers are known to drive strong shocks into the intracluster medium and generate turbulence. These shocks and turbulence accelerate relativistic particles, compress magnetic fields and heat the intracluster medium. At the same time, the cluster merger results in a transient boost of the cluster X-ray luminosity and SZ effect.

A clear observational connection appears to exist between mergers and the presence of large regions of diffuse synchrotron emission leading to the potential use of these radio signatures as a merge-o-meter for large cluster samples. Unfortunately, we still do not understand the details of the particle acceleration mechanism(s).

In order to better understand the processes at work, we have undertaken a detailed radio and X-ray study of the well known merging cluster Abell 2256. The radio maps reveal a wealth of total intensity and polarization structure within this system including highly polarized Mpc scale radio relics, a Mpc scale radio halo and numerous steep spectrum synchrotron filaments with lengths of order 200 kpc. Spectral index maps reveal spectral gradients across the relics and suggest the presence of a Mach 2.6 shock near the north-west boundary of the relics. XMM-Newton pressure maps show a low pressure core co-incident with the radio halo emission, while temperature maps reveal two cold fronts with similar directions of motion.

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