High energy X-ray and gamma-ray observations of galaxy clusters

Galaxy clusters are the largest and most massive gravitationally bound systems in the Universe. Galaxy clusters are bright sources of X-rays owing to thermal emission of the hot intracluster medium. Furthermore, galaxy clusters might be sources of TeV gamma rays emitted by non-thermal high-energy protons and electrons accelerated by large scale structure formation shocks, galactic winds, or active galactic nuclei. In addition, gamma rays may be produced in dark matter particle annihilation processes at the cluster cores. I report on observations of the galaxy cluster 3C 129 with the XMM-Newton X-ray observatory. These observations have two major aims. First. I search for interactions of the nonthermal plasma of the large head-tail radio galaxy 3C 129 with the thermal intracluster medium. Second, I study the X-ray emission from the core of the radio galaxy. I derive an upper limit on the deficit in the ICM plasma due to the interacting radio jet which is less than the expected 10%. Additionally, I find an excess in the core emission over the Chandra observations, suggesting the presence of extended emission near the core. I also report on the search for TeV emission from the galaxy clusters Perseus and Abell 2029 using the 10 m Whipple Cherenkov telescope during the 2003-2004 and 2004-2005 observing seasons. I apply a two-dimensional analysis technique to scrutinize the clusters for TeV emission, first determining flux upper limits on TeV gamma-ray emission from point sources within the clusters then deriving upper limits on the extended cluster emission. I subsequently compare the flux upper limits with EGRET upper limits at 100 MeV and theoretical models. Assuming that the gamma-ray surface brightness profile mimics that of the thermal X-ray emission and that the spectrum of cluster cosmic rays extends all the way from thermal energies to multi-TeV energies with a differential spectral index of -2.1, the results imply that the cosmic ray proton energy density is less than 7.9% of the thermal energy density for the Perseus cluster.