in Proc. of the 1st GLAST Symposium, Feb 5-8, 2007, Stanford, AIP, Eds. S. Ritz, P. F. Michelson, and C. Meegan
astro-ph/0704.2888

For a PDF version of the article, click here.

Abstract. One way to understand the nonthermal history of the universe is by establishing the origins of the unresolved and truly diffuse extragalactic γ rays. Dim blazars and radio / γ galaxies certainly make an important contribution to the galactic γ-ray background given the EGRET discoveries, and previous treatments are reviewed and compared with a new analysis. Studies of the γ-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 γ-ray source class seems required from the predicted aggregate intensity compared with the measured intensity.

Keywords: gamma-rays - blazars - background radiations
PACS: 95.85.Pw, 98.54.Cm, 98.62.Nx, 98.70.Rz, 98.70.Vc

Table of Contents

• INTRODUCTION
• BLAZARS AND RADIO / γ GALAXIES
• STAR-FORMING GALAXIES
• CLUSTERS OF GALAXIES
• GAMMA RAY BURSTS
• ADDITIONAL CONTRIBUTIONS
• REFERENCES