A radio and X-ray study of the merging cluster A2319

Abstract

A2319 is a massive, merging galaxy cluster with a previously detected radio halo that roughly follows the X-ray emitting gas. We present the results from recent observations of A2319 at ∼20 cm with the Karl G. Jansky Very Large Array and a re-analysis of the X-ray observations from XMM-Newton, to investigate the interactions between the thermal and non-thermal components of the intracluster medium. We confirm previous reports of an X-ray cold front, and identify a distinct core to the radio halo, ∼800 kpc in extent, that is strikingly similar in morphology to the X-ray emission, and drops sharply in brightness at the cold front. We also detect radio emission trailing off from the core that blends smoothly into the ∼2 Mpc halo detected with the Green Bank Telescope (GBT). We speculate on the possible mechanisms for such a two-component radio halo, with sloshing playing a dominant role in the core. By directly comparing the X-ray and radio emission, we find that a hadronic origin for the cosmic ray electrons responsible for the radio halo would require a magnetic field and/or cosmic ray proton distribution that increases with radial distance from the cluster centre, and is therefore disfavoured.