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Title: Models of the contribution of blazars to the anisotropy of the extragalactic diffuse gamma-ray background

Abstract

We study the relation between the measured anisotropies in the extragalactic diffuse gamma-ray background (DGRB) and the DGRB spectral intensity, and their potential origin from the unresolved blazar population. Using a physical-evolution model for blazars with a luminosity dependent density evolution (LDDE) and an observationally-determined luminosity-dependent blazar spectral energy distribution (SED), we find that blazars can account for the observed anisotropy of the DGRB consistent with their observed source-count distribution, but are in turn constrained in contributing significantly to the observed DGRB intensity. For the best-fit LDDE model accounting for the DGRB anisotropy and source-count distribution, blazars only contribute 5.9{sup +2.1}{sub −1.0}% (68% CL) of the DGRB intensity above 1 GeV. Requiring a higher fraction of the DGRB intensity contribution by blazars overproduces the DGRB anisotropy, and therefore blazars in the LDDE+SED-sequence model cannot simultaneously account for the DGRB intensity as well as anisotropy. We discuss the limitations of LDDE models. However, these models do not require the many unjustified and observationally-inconsistent simplifying assumptions — including a single power law for all blazar spectra and a simple broken power-law model for their source-count distribution — that are present in much previous work.

Authors:
 [1];  [2]
  1. Maryland Center for Fundamental Physics and Joint Space-Science Institute, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)
  2. Center for Cosmology, Department of Physics and Astronomy, University of California – Irvine, Irvine, California, 92697 (United States)
Publication Date:
OSTI Identifier:
22279811
Resource Type:
Journal Article
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2012; Journal Issue: 11; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; ASTROPHYSICS; COSMOLOGY; DENSITY; ENERGY SPECTRA; EVOLUTION; GAMMA RADIATION; GEV RANGE; LUMINOSITY; POTENTIALS; QUASARS

Citation Formats

Harding, J. Patrick, and Abazajian, Kevork N., E-mail: hard0923@umd.edu, E-mail: kevork@uci.edu. Models of the contribution of blazars to the anisotropy of the extragalactic diffuse gamma-ray background. United States: N. p., 2012. Web. doi:10.1088/1475-7516/2012/11/026.
Harding, J. Patrick, & Abazajian, Kevork N., E-mail: hard0923@umd.edu, E-mail: kevork@uci.edu. Models of the contribution of blazars to the anisotropy of the extragalactic diffuse gamma-ray background. United States. doi:10.1088/1475-7516/2012/11/026.
Harding, J. Patrick, and Abazajian, Kevork N., E-mail: hard0923@umd.edu, E-mail: kevork@uci.edu. Thu . "Models of the contribution of blazars to the anisotropy of the extragalactic diffuse gamma-ray background". United States. doi:10.1088/1475-7516/2012/11/026.
@article{osti_22279811,
title = {Models of the contribution of blazars to the anisotropy of the extragalactic diffuse gamma-ray background},
author = {Harding, J. Patrick and Abazajian, Kevork N., E-mail: hard0923@umd.edu, E-mail: kevork@uci.edu},
abstractNote = {We study the relation between the measured anisotropies in the extragalactic diffuse gamma-ray background (DGRB) and the DGRB spectral intensity, and their potential origin from the unresolved blazar population. Using a physical-evolution model for blazars with a luminosity dependent density evolution (LDDE) and an observationally-determined luminosity-dependent blazar spectral energy distribution (SED), we find that blazars can account for the observed anisotropy of the DGRB consistent with their observed source-count distribution, but are in turn constrained in contributing significantly to the observed DGRB intensity. For the best-fit LDDE model accounting for the DGRB anisotropy and source-count distribution, blazars only contribute 5.9{sup +2.1}{sub −1.0}% (68% CL) of the DGRB intensity above 1 GeV. Requiring a higher fraction of the DGRB intensity contribution by blazars overproduces the DGRB anisotropy, and therefore blazars in the LDDE+SED-sequence model cannot simultaneously account for the DGRB intensity as well as anisotropy. We discuss the limitations of LDDE models. However, these models do not require the many unjustified and observationally-inconsistent simplifying assumptions — including a single power law for all blazar spectra and a simple broken power-law model for their source-count distribution — that are present in much previous work.},
doi = {10.1088/1475-7516/2012/11/026},
journal = {Journal of Cosmology and Astroparticle Physics},
issn = {1475-7516},
number = 11,
volume = 2012,
place = {United States},
year = {2012},
month = {11}
}