Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-06-15
High Energy Gamma-Ray Astronomy: 2nd International Symposium, Proceedings of the conference held 26-30 July 2004 in Heidelberg
Astronomy and Astrophysics
Astrophysics
6 pages, 3 figures, 1 table
Scientific paper
10.1063/1.1878467
The GALPROP model for cosmic-ray propagation is able to make explicit predictions for the distribution of galactic diffuse gamma-rays. We compare different propagation models with gamma-ray spectra measured by EGRET for various regions of the sky. This allows sensitive tests of alternative explanations for the apparent excess emission observed at GeV gamma-rays. We find that a population of hard-spectrum gamma-ray sources cannot be solely responsible for the excess since it also appears at high latitudes; on the other hand a hard cosmic-ray electron spectrum cannot explain the gamma-ray excess in the inner Galaxy. By normalizing the cosmic ray spectra within reasonable bounds under preservation of their shape we are able to obtain our best prediction of the Galactic component of diffuse gamma rays, and show that away from the Galactic plane it gives an accurate prediction of the observed gamma-ray intensities. On this basis we reevaluate the extragalactic gamma-ray background. We find that for some energies previous work underestimated the Galactic contribution and hence overestimated the background. The new EGRB spectrum shows a positive curvature similar to that expected for models of the extragalactic gamma-ray emission based on contributions from unresolved blazars.
Moskalenko Igor V.
Reimer Olaf
Strong Andrew W.
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