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The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background

Venters, Tonia M. and Pavlidou, Vasiliki (2011) The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background. Astrophysical Journal, 737 (2). Art. No. 80. ISSN 0004-637X.

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The spectral shapes of the contributions of different classes of unresolved gamma-ray emitters can provide insight into their relative contributions to the extragalactic gamma-ray background (EGB) and the natures of their spectra at GeV energies. We calculate the spectral shapes of the contributions to the EGB arising from BL Lac objects and flat-spectrum radio quasars assuming blazar spectra can be described as broken power laws. We fit the resulting total blazar spectral shape to the Fermi Large Area Telescope measurements of the EGB, finding that the best-fit shape reproduces well the shape of the Fermi EGB for various break scenarios. We conclude that a scenario in which the contribution of blazars is dominant cannot be excluded on spectral grounds alone, even if spectral breaks are shown to be common among Fermi blazars. We also find that while the observation of a featureless (within uncertainties) power-law EGB spectrum by Fermi does not necessarily imply a single class of contributing unresolved sources with featureless individual spectra, such an observation and the collective spectra of the separate contributing populations determine the ratios of their contributions. As such, a comparison with studies including blazar gamma-ray luminosity functions could have profound implications for the blazar contribution to the EGB, blazar evolution, and blazar gamma-ray spectra and emission.

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Additional Information:© 2011 The American Astronomical Society. Received 2010 October 13; accepted 2011 May 31; published 2011 August 8. We gratefully acknowledge enlightening discussions with Floyd Stecker. T.M.V. was supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with NASA. V.P. acknowledges support for this work provided by NASA 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. This work was partially supported by NASA through the Fermi GI Program grant number NNX09AT74G.
Funding AgencyGrant Number
NASA Einstein Postdoctoral Fellowship PF8-90060
NASA Chandra X-ray CenterNAS8-03060
NASA Fermi Guest InvestigatorNNX09AT74G
Subject Keywords:galaxies: active; gamma rays: diffuse background; gamma rays: galaxies
Issue or Number:2
Classification Code:PACS: 95.85.Pw; 98.70.Rz; 98.54.Aj; 98.54.Cm; 98.70.Vc
Record Number:CaltechAUTHORS:20110912-084535422
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Official Citation:The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background Tonia M. Venters and Vasiliki Pavlidou 2011 ApJ 737 80
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:25289
Deposited By: Ruth Sustaita
Deposited On:12 Sep 2011 16:51
Last Modified:03 Oct 2019 03:04

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