Search for TeV Emission from Galaxy Clusters

Galaxy clusters are predicted to be emitters of high energy gamma rays due to the relativistic particles accelerated by merger and accretion shocks. The gamma rays are produced either by inverse Compton scattering of relativistic electrons or by high energy proton cascades due to p-p collisions. Some predictions of TeV fluxes from clusters such as Coma are near the sensitivity of current detectors. In this paper we report upper limits for TeV gamma-ray emission from clusters using data from the Milagro gamma-ray observatory. Milagro is a unique TeV gamma-ray observatory, located in the mountains above Los Alamos, NM, that has a ~2 sr field of view and > 90% duty factor, making it ideal for surveying the sky for new classes of TeV astrophysical sources.