Population studies of the unidentified EGRET sources

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

Research output: Contribution to journalArticlepeer-review


The third EGRET catalog contains a large number of unidentified sources. This subset of objects is expected to include known gamma-ray emitters of Galactic origin such as pulsars and supernova remnants, in addition to an extragalactic population of blazars. However, current data allows the intriguing possibility that some of these objects may represent a new class of yet undiscovered gamma-ray sources. Many theoretically motivated candidate emitters (e.g. clumps of annihilating dark matter particles) have been suggested to account for these detections. We take a new approach to determine to what extent this population is Galactic and to investigate the nature of the possible Galactic component. By assuming that galaxies similar to the Milky Way should host comparable populations of objects, we constrain the allowed Galactic abundance and distribution of various classes of gamma-ray sources using the EGRET data set. We find it is highly improbable that a large number of the unidentified sources are members of a Galactic halo population, but that a distribution of the sources entirely in the disk and bulge is plausible. Finally, we discuss the additional constraints and new insights that GLAST will provide.

Original languageEnglish (US)
Pages (from-to)43-49
Number of pages7
JournalAstrophysics and Space Science
Issue number1-4
StatePublished - Jun 2007


  • Gamma-rays: observation
  • Gamma-rays: theory
  • Gamma-rays: unidentified sources

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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