On the evolution of giant radio halos and their connection with cluster mergers

Understand

Giant radio halos are diffuse, Mpc-scale, synchrotron sources located in the central regions of galaxy clusters and provide the most relevant example of cluster non-thermal activity.

• Radio and X-ray surveys allow to investigate the statistics of halos and may contribute to constrain their origin and evolution.
• We investigate the distribution of clusters in the plane X-ray (thermal, L_X) vs synchrotron (P_{1.4})luminosity, where clusters hosting giant radio halos trace the P_{1.4}--L_X correlation and clusters without radio halos populate a region that is well separated from that spanned by the above correlation.
• The connection between radio halos and cluster mergers suggests that the cluster Mpc-scale synchrotron emission is amplified during these mergers and then suppressed when clusters become more dynamically relaxed.