Cosmic Gamma-ray Background from Star-forming Galaxies
Abstract
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.
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.Attached Files
Published - Fields2010p11730Astrophys_J_Lett.pdf
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Additional details
- Eprint ID
- 20658
- Resolver ID
- CaltechAUTHORS:20101104-075702315
- NNX09AT74G
- NASA/Fermi GI Program
- NNX09AU01G
- NASA/Fermi GI Program
- NNX10AC86G
- Astrophysics Theory Program
- PF8-90060
- NASA/Einstein Postdoctoral Fellowship
- NAS8-03060
- NASA
- Provincial Secretariat for Science and Technological Development
- 141002B
- Ministry of Science of the Republic of Serbia
- Created
-
2010-11-04Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field