The Extragalactic Gamma Ray Background
arXiv:0704.2888 · doi:10.1063/1.2757282
Abstract
One way to understand the nonthermal history of the universe is by establishing the origins of the unresolved and truly diffuse extragalactic gamma rays. Dim blazars and radio/gamma galaxies certainly make an important contribution to the galactic gamma-ray background given the EGRET discoveries, and previous treatments are reviewed and compared with a new analysis. Studies of the gamma-ray intensity from cosmic rays in star-forming galaxies and from structure formation shocks, as well as from dim GRBs, are briefly reviewed. A new hard gamma-ray source class seems required from the predicted aggregate intensity compared with the measured intensity.
5 pages, 1 figures, in Proc. of the 1st GLAST Symposium, Feb 5-8, 2007, Stanford, AIP, Eds. S. Ritz, P. F. Michelson, and C. Meegan; references added, minor changes