Constraints on Galactic populations from the unidentified EGRET sources

Jennifer M. Siegal-Gaskins, Vasiliki Pavlidou, Angela V. Olinto, Carolyn Brown, Brian D. Fields

Research output: Chapter in Book/Report/Conference proceedingConference contribution


A significant fraction of the sources in the third EGRET catalog have not yet been identified with a low-energy counterpart. We evaluate the plausibility of a Galactic population accounting for some or all of the unidentified EGRET sources by making the simple assumption that galaxies similar to the Milky Way host comparable populations of gamma-ray emitters. Rather than focusing on the properties of a specific candidate emitter, we constrain the abundance and spatial distribution of proposed Galactic populations. We find that it is highly improbable that the unidentified EGRET sources contain more than a handful of members of a Galactic halo population, but that current observations are consistent with all of these sources being Galactic objects if they reside entirely in the disk and bulge. We discuss the additional constraints and new insights into the nature of Galactic gamma-ray emitting populations that GLAST is expected to provide.

Original languageEnglish (US)
Title of host publicationFirst GLAST Symposium
PublisherAmerican Institute of Physics Inc.
Number of pages3
ISBN (Print)9780735404311
StatePublished - 2007

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


  • Gamma-rays: Observations
  • Gamma-rays: Theory
  • Unidentified sources

ASJC Scopus subject areas

  • General Physics and Astronomy


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