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Cosmic Gamma-ray Background from Star-forming Galaxies

Fields, Brian D. and Pavlidou, Vasiliki and Prodanović, Tijana (2010) Cosmic Gamma-ray Background from Star-forming Galaxies. Astrophysical Journal Letters, 722 (2). L199-L203. ISSN 2041-8205.

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The origin of the extragalactic gamma-ray background is a pressing cosmological mystery. The Fermi Gamma-Ray Space Telescope has recently measured the intensity and spectrum of this background; both are substantially different from previous measurements. We present a novel calculation of the gamma-ray background from normal star-forming galaxies. Contrary to long-standing expectations, we find that numerous but individually faint normal galaxies may comprise the bulk of the Fermi signal, rather than rare but intrinsically bright active galaxies. This result has wide-ranging implications, including: the possibility to probe the cosmic star formation history with gamma rays; the ability to infer the cosmological evolution of cosmic rays and galactic magnetic fields; and an increased likelihood of identifying subdominant components from rare sources (e.g., dark matter clumps) through their large anisotropy.

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Additional Information:© 2010 The American Astronomical Society. Received 2010 May 17; accepted 2010 September 16; published 2010 October 1. It is a pleasure to thank Marco Ajello, Chuck Dermer, Hai Fu, Troy Porter, and Andy Strong for stimulating discussions. B.D.F. thanks the Goddard Space Flight Center for hospitality while some of this work was done. This work was partially supported by NASA, via Fermi GI Program grants NNX09AT74G and NNX09AU01G, and the Astrophysics Theory Program through award NNX10AC86G. V.P. acknowledges NASA support through Einstein Postdoctoral Fellowship grant number PF8-90060 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. V.P. thanks the Physics Department at the University of Crete for their hospitality during part of this work. The work of T.P. is supported in part by the Provincial Secretariat for Science and Technological Development, and by the Ministry of Science of the Republic of Serbia under project 141002B.
Funding AgencyGrant Number
NASA/Fermi GI ProgramNNX09AT74G
NASA/Fermi GI ProgramNNX09AU01G
Astrophysics Theory ProgramNNX10AC86G
NASA/Einstein Postdoctoral FellowshipPF8-90060
Provincial Secretariat for Science and Technological DevelopmentUNSPECIFIED
Ministry of Science of the Republic of Serbia141002B
Subject Keywords:cosmic rays; galaxies: star formation; gamma rays: diffuse background; gamma rays: galaxies
Issue or Number:2
Classification Code:PACS: 98.70.Rz; 98.70.Vc; 98.62.Ai; 98.62.En; 98.70.Sa
Record Number:CaltechAUTHORS:20101104-075702315
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Official Citation:Brian D. Fields et al 2010 ApJ 722 L199 doi: 10.1088/2041-8205/722/2/L199
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20658
Deposited By: Ruth Sustaita
Deposited On:04 Nov 2010 15:37
Last Modified:03 Oct 2019 02:13

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