Nonthermal Emission from Accreting and Merging Clusters of Galaxies

We compare the nonthermal emission from clusters of galaxies undergoing minor mergers (“accreting” clusters) and major mergers (“merging” clusters). We define major mergers as the mergers that change the inner dark matter structure of clusters; minor mergers are all others. For accreting clusters, the radial distribution of the nonthermal emission in the clusters is also calculated. The relativistic electrons, which are the origin of the nonthermal radiation through inverse Compton (IC) and synchrotron emission, are assumed to be accelerated at shocks produced by accretion or mergers. We estimate the typical accretion rate and merger probability according to a hierarchical clustering model. We predict that in the inner region of accreting clusters the nonthermal emission has a flat spatial distribution at all frequency. For synchrotron and hard X-ray emissions, we predict an increase of the emissions at the cluster edge due to accretion. We show that the total luminosity of IC emission from accreting and merging clusters are similar. On the other hand, the luminosity of synchrotron radio emission of Present address: Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818