Thermal and nonthermal effects in merging clusters of galaxies

This thesis presents several studies of merging clusters of galaxies at X-ray and radio wavelengths, and analyzes the observable effects of mergers on the intracluster medium (ICM). It focuses primarily on nonthermal radio halos and relics and on the thermal effects of moving cold cores of gas propagating through the ICM. We present a systematic search for diffuse radio halos and relics in all of the Abell clusters that are visible in the Westerbork Northern Sky Survey. We found 7 candidates for which we provide the first evidence of diffuse radio emission. We also investigate the correlation between cluster X-ray luminosity and radio power of halos and discuss the implications of this correlation for future surveys. An analysis of Abell 2199 sets strong upper limits on the radio flux from the cluster. These limits are used to constrain the cluster magnetic field by requiring consistency between the radio flux and the hard X-ray (HXR) flux observed by BeppoSAX, assuming that the HXR, excess is inverse Compton scattering of cosmic microwave background photons by relativistic electrons in the ICM. The magnetic field must be very weak in order to avoid producing an observable radio halo. We also consider a nonthermal bremsstrahlung model for the HXR excess. In X-rays, the present an analysis of a highly asymmetric cluster merger from a Chandra observation of Abell 85. The merger shows significant disruption of the less massive subcluster from ram pressure. A cold core, coincident with the cD galaxy, is observed in the subcluster. We derive dynamical information from the motion of the cold core through the main cluster's ICM and construct a consistent kinematic model for the merger based on this dynamical analysis. Also in X-rays, we present an analysis of a Chandra observation of Abell 2034. The cluster has signatures of an ongoing merger, including a cold front and significant heating of the intracluster medium. We again derive dynamical information from the cold front. Emission to the south of the cluster, previously thought to be a merging subcluster, may be a moderate redshift background cluster seen in projection.