Unidentified EGRET sources and the extragalactic gamma-ray background |
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Authors: | Vasiliki Pavlidou Jennifer M. Siegal-Gaskins Carolyn Brown Brian D. Fields Angela V. Olinto |
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Affiliation: | 1. The University of Chicago, Chicago, IL, 60637, USA 2. University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
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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. |
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