Radio Observations of Cluster Mergers
  A very important aspect of the radio emission from galaxy clusters is represented by the diffuse radio sources associated with the intracluster medium: radio halos and relics. These radio sources indicate the existence of large scale magnetic fields and of a population of relativistic electrons in the cluster volume. The observational results provide evidence that these phenomena are related to cluster merger activity, which supplies the energy to the reacceleration of the radiating particles. The details of the halo-merger connection are investigated through the comparison between the radio and the X-ray emission. 
Luigina Feretti (Ist. Radioastronomia, Bologna)