| Description: | Radio halos are Mpc-scale diffuse synchrotron sources detected in merging galaxy clusters. Their origin is associated with the formation process of the cluster, where part of the merger kinetic energy is dissipated into non-thermal components. In order to recover their extended and low-brightness emission, radio halos have historically been studied at low-resolution. However, the new generation of radio interferometers is now allowing us to study radio halos in unprecedented detail. In this talk, I will report on recent advancements in the study of radio halos. In particular, I will focus on the discovery of substructures and surface brightness discontinuities in the diffuse radio emission detected with MeerKAT and LOFAR. The radio surface brightness discontinuities in radio halos are remarkably similar to those commonly observed in X-rays for shocks and cold fronts in merging clusters, while the co-location between radio and X-rays edges demonstrates the tight relation between thermal and non-thermal components in the intra-cluster medium. In addition to edges, radio halos can also show thin filamentary structures. This is the case of the Abell 2255 cluster, which is currently being observed with LOFAR for more than 300 h. One of the goals of this ultra-deep observation is indeed to investigate the origin of these enigmatic features. |
