Egret observations of the extragalactic gamma-ray emission

P. Sreekumar, D.L. Bertsch, B.L. Dingus, J.A. Esposito, C.E. Fichtel, R.C. Hartman, S.D. Hunter, G. Kanbach, D.A. Kniffen, Y.C. Lin, H.A. Mayer-Hasselwander, P.F. Michelson, C. von Montigny, A. Mucke, R. Mukherjee, P.L. Nolan, M. Pohl, O. Reimer, E. Schneid, J.G. StacyF.W. Stecker, D.J. Thompson, T.D. Willis

    Research output: Contribution to journalJournal articleResearchpeer-review


    The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by EGRET aboard the Compton Gamma Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions with the local interstellar gas and radiation, as well as an almost uniformly distributed component that is generally believed to originate outside the Galaxy. Through a careful study and removal of the Galactic diffuse emission, the flux, spectrum, and uniformity of the extragalactic emission are deduced. The analysis indicates that the extragalactic emission is well described by a power-law photon spectrum with an index of -(2.10 +/- 0.03) in the 30 MeV to 100 GeV energy range. No large-scale spatial anisotropy or changes in the energy spectrum are observed in the deduced extragalactic emission. The most likely explanation for the origin of this extragalactic high-energy gamma-ray emission is that it arises primarily from unresolved gamma-ray-emitting blazars.
    Original languageEnglish
    JournalAstrophysical Journal
    Issue number2
    Pages (from-to)523-534
    Publication statusPublished - 1998


    • gamma rays, observations
    • surveys
    • diffuse radiation


    Dive into the research topics of 'Egret observations of the extragalactic gamma-ray emission'. Together they form a unique fingerprint.

    Cite this