A New Estimate of the Extragalactic Gamma-Ray Background from EGRET Data

Abstract

We use the GALPROP model for cosmic-ray (CR) propagation to obtain our best prediction of the Galactic component of gamma rays, and show that away from the Galactic plane it gives an accurate prediction of the observed EGRET intensities. On this basis we re-evaluate the isotropic extragalactic gamma-ray background (EGRB). We find that for some energies previous work underestimated the Galactic contribution and hence overestimated the background. Our new EGRB spectrum shows a positive curvature similar to that expected for models of the extragalactic emission based on the blazar population.