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Unidentified EGRET sources and the extragalactic gamma-ray background

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

Abstract

The large majority of EGRET point sources remain to this day without an identified low-energy counterpart. Whatever the nature of the EGRET unidentified sources, faint unresolved objects of the same class must have a contribution to the diffuse gamma-ray background: if most unidentified objects are extragalactic, faint unresolved sources of the same class contribute to the background, as a distinct extragalactic population; on the other hand, if most unidentified sources are Galactic, their counterparts in external galaxies will contribute to the unresolved emission from these systems. Understanding this component of the gamma-ray background, along with other guaranteed contributions from known sources, is essential in any attempt to use gamma-ray observations to constrain exotic high-energy physics. Here, we follow an empirical approach to estimate whether a potential contribution of unidentified sources to the extragalactic gamma-ray background is likely to be important, and we find that it is. Additionally, we comment on how the anticipated GLAST measurement of the diffuse gamma-ray background will change, depending on the nature of the majority of these sources.

Keywords

Gamma rays: observations Gamma-ray sources: astronomical Radiation sources: unidentified 

PACS

95.85.Pw 98.70.Rz 98.70.-f 

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Copyright information

© Springer 2007

Authors and Affiliations

  • Vasiliki Pavlidou
    • 1
  • Jennifer M. Siegal-Gaskins
    • 1
  • Carolyn Brown
    • 1
  • Brian D. Fields
    • 2
  • Angela V. Olinto
    • 1
  1. 1.The University of ChicagoChicagoUSA
  2. 2.University of Illinois at Urbana-ChampaignUrbanaUSA

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