Description
Abell 2219 (z = 0.225) is only the second galaxy cluster merger where both the forward and reverse shock fronts are identified with X-ray temperature and density measurements and one of only a handful with any shock fronts unambiguous detected as both temperature and density discontinuities. The reason for this rarity is the requirement of a near plane-of-sky merger, to mitigate the effects of projection, and also the inherently low X-ray surface brightness of shocked regions in the outskirts of clusters. These sharp discontinuities, along with cluster cold fronts, have the potential to constrain micro-scale transport processes in the hot intra-cluster medium which currently present a sharp discontinuity in our understanding. Revealing this important physics requires the superb spatial resolution of Chandra.
Chandra observations of Abell 2219 have revealed this system is in the early throes of a violent merger; the cluster and sub-cluster are currently at (or marginally before) core passage. Abell 2219 is also one of the hottest and most luminous (more than twice as bright in the X-rays as either the Bullet cluster or Abell 520) galaxy clusters known, with a system temperature of 12 keV, and unusually, a hot yet dense core, suggesting evidence for ongoing shock activity at the core.
In this work we analyse the shock fronts to provide constraints on particle acceleration; relate the spectral index variations in the radio halo to the X-ray features; and, characterize the properties of the disrupted sub-cluster core.
