Unresolved unidentified source contribution to the gamma-ray background

V. Pavlidou, J. M. Siegal-Gaskins, B. D. Fields, A. V. Olinto, C. Brown

Research output: Contribution to journalArticlepeer-review


The large majority of EGRET point sources remain without an identified low-energy counterpart, and a large fraction of these sources are most likely extragalactic. Whatever the nature of the extragalactic EGRET unidentified sources, faint unresolved objects of the same class must have a contribution to the diffuse extragalactic gamma-ray background (EGRB). Understanding this component of the EGRB, along with other guaranteed contributions from known sources, is essential if we are to use this emission to constrain exotic high-energy physics. Here, we follow an empirical approach to estimate whether a potential contribution of unidentified sources to the EGRB is likely to be important, and we find that it is. In addition, we show how upcoming GLAST observations of EGRET unidentified sources, as well as of their fainter counterparts, can be combined with GLAST observations of the Galactic and extragalactic diffuse backgrounds to shed light on the nature of the EGRET unidentified sources even without any positional association of such sources with low-energy counterparts.

Original languageEnglish (US)
Pages (from-to)27-36
Number of pages10
JournalAstrophysical Journal
Issue number1
StatePublished - Apr 10 2008


  • Diffuse radiation
  • Gamma rays: observations
  • Gamma rays: theory

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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