Presentation #108.02 in the session “Understanding Extragalactic Jets: Simulations and Observations”.
Central AGNs in cool-core clusters emit jets and blow radio bubbles. On larger scales, some cool cores host diffuse radio synchrotron emission that fills uniformly the whole core — the so-called radio minihalos. Their existence requires magnetic fields and ultra-relativistic electrons to be distributed throughout a large fraction of the cluster central core. Until recently, minihalos were thought to be rare sources, but our analysis of a complete Planck mass-selected cluster sample shows that almost all cool cores in massive clusters possess a radio minihalo. It has been proposed that sloshing motions of the cool gas in the core is responsible for the origin of minihalos, based on coincidence between radio and X-ray features. Sloshing-induced turbulence may accelerate seed electrons (e.g., aged relativistic electrons injected by past outbursts of the central AGN or left behind by a nearby tailed radio galaxy) and produce diffuse radio synchrotron emission that is spatially coincident with the sloshing region. Thus, radio minihalos may be the ultimate depository of the relativistic matter ejected by the central AGN over the cluster lifetime. In this talk, I will present examples of minihalos supporting the sloshing scenario. I will also present results of our statistical study of minihalos and their correlation with the X-ray and Sunyaev-Zel’dovich (SZ) properties of the cluster hosts.