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Joint anisotropy and source count constraints on the contribution of blazars to the diffuse gamma-ray background

Cuoco, A. and Komatsu, E. and Siegal-Gaskins, J. M. (2012) Joint anisotropy and source count constraints on the contribution of blazars to the diffuse gamma-ray background. Physical Review D, 86 (6). Art. No. 063004. ISSN 0556-2821.

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We place new constraints on the contribution of blazars to the large-scale isotropic gamma-ray background (IGRB) by jointly analyzing the measured source count distribution (logN-logS) of blazars and the measured intensity and anisotropy of the IGRB. We find that these measurements point to a consistent scenario in which unresolved blazars make ≲20% of the IGRB intensity at 1–10 GeV while accounting for the majority of the measured anisotropy in that energy band. These results indicate that the remaining fraction of the IGRB intensity is made by a component with a low level of intrinsic anisotropy. We determine upper limits on the anisotropy from nonblazar sources, adopting the best-fit parameters of the measured source count distribution to calculate the unresolved blazar anisotropy. In addition, we show that the anisotropy measurement excludes some recently proposed models of the unresolved blazar population.

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Additional Information:© 2012 American Physical Society. Received 7 March 2012; published 5 September 2012. We thank M. Ajello, T. Venters, F. Stecker, and K. Abazajian for useful comments and interesting discussions. EK is supported in part by NSF Grants No. AST-0807649 and No. PHY-0758153 and NASA Grant No. NNX08AL43G. JSG acknowledges support from NASA through Einstein Postdoctoral Fellowship Grant No. PF1-120089 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under Contract No. NAS8-03060.
Funding AgencyGrant Number
NASA Einstein Postdoctoral Fellowship PF1-120089
NASA Chandra X-ray CenterNAS8-03060
Classification Code:PACS: 98.70.Rz, 98.70.Vc
Record Number:CaltechAUTHORS:20121011-092528097
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34841
Deposited By: Tony Diaz
Deposited On:11 Oct 2012 19:40
Last Modified:27 Dec 2012 02:51

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