Multiwavelength observations of clusters of galaxies and the role of   cluster mergers
  Some clusters of galaxies have been identified as powerful sources of non-thermal radiation, from the radio to X-ray wavelengths. The classical models proposed for the explanation of this radiation usually require large energy densities in cosmic rays in the intracluster medium and magnetic fields much lower that those measured using the Faraday rotation. We study here the role that mergers of clusters of galaxies may play in the generation of the non-thermal radiation, and we seek for additional observable consequences of the model. We find that if hard X-rays and radio radiation are respectively interpreted as inverse Compton scattering (ICS) and synchrotron emission of relativistic electrons, large gamma ray fluxes are produced, and for the Coma cluster, where upper limits are available, these limits are exceeded. We also discuss an alternative and testable model that naturally solves the problems mentioned above. 
Pasquale Blasi