Seeding Radio Relics by Turbulent Transport of AGN Bubble Material
Abstract
Radio relics, Mpc-long arc-like structures in the outskirts of galaxy clusters, are believed to arise from relativistic electrons emitting synchrotron radiation in the cluster magnetic field. These features often coincide with shock fronts seen in X-ray observations of the intracluster medium which are produced by mergers. For some time, the prevailing theory has been that the electron population which produces the radio relic is accelerated from the thermal pool by diffusive shock acceleration. However, cluster merger shocks are relatively weak, and it is not clear how the aforementioned mechanism could be efficient enough. An alternative proposal is that the shock reaccelerates a pre-existing population of mildly relativistic electrons. As a potential source for thispopulation, we propose that cosmic-ray electrons contained within AGN-blown bubbles are transported to larger radii and spread out across a large azimuthal distance by motions within the cluster gas. To test this hypothesis, we perform MHD simulations of AGN feedback using the Arepo code within clusters with two different types of gas motions, sloshing and merger-driven turbulence. We show that in each case the gas motions are able to produce distributions of cosmic rays which are plausible sources for radio relics by subsequent reacceleration by shocks.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23514403Z