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The gamma-ray-flux PDF from galactic halo substructure

Lee, Samuel K. and Ando, Shin'ichiro and Kamionkowski, Marc (2009) The gamma-ray-flux PDF from galactic halo substructure. Journal of Cosmology and Astroparticle Physics, 2009 (07). Art. No. 007. ISSN 1475-7516.

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One of the targets of the recently launched Fermi Gamma-ray Space Telescope is a diffuse gamma-ray background from dark-matter annihilation or decay in the Galactic halo. N-body simulations and theoretical arguments suggest that the dark matter in the Galactic halo may be clumped into substructure, rather than smoothly distributed. Here we propose the gamma-ray-flux probability distribution function (PDF) as a probe of substructure in the Galactic halo. We calculate this PDF for a phenomenological model of halo substructure and determine the regions of the substructure parameter space in which the PDF may be distinguished from the PDF for a smooth distribution of dark matter. In principle, the PDF allows a statistical detection of substructure, even if individual halos cannot be detected. It may also allow detection of substructure on the smallest microhalo mass scales, ~ M_⊕, for weakly-interacting massive particles (WIMPs). Furthermore, it may also provide a method to measure the substructure mass function. However, an analysis that assumes a typical halo substructure model and a conservative estimate of the diffuse background suggests that the substructure PDF may not be detectable in the lifespan of Fermi in the specific case that the WIMP is a neutralino. Nevertheless, for a large range of substructure, WIMP annihilation, and diffuse background models, PDF analysis may provide a clear signature of substructure.

Item Type:Article
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URLURL TypeDescription Paper
Kamionkowski, Marc0000-0001-7018-2055
Additional Information:© Institute of Physics and SISSA 2009. Received 11 October 2008, accepted for publication 11 June 2009. Published 3 July 2009. This work was supported by the Sherman Fairchild Foundation (SA), DoE DE-FG03-92-ER40701, and the Gordon and Betty Moore Foundation.
Group:TAPIR, Moore Center for Theoretical Cosmology and Physics
Funding AgencyGrant Number
Sherman Fairchild FoundationUNSPECIFIED
Department of Energy (DOE)DE-FG03-92-ER40701
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:dark matter; structure of galaxies
Issue or Number:07
Record Number:CaltechAUTHORS:20090901-161606701
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Official Citation:The gamma-ray-flux PDF from galactic halo substructure Samuel K. Lee, Shin'ichiro Ando and Marc Kamionkowski JCAP07(2009)007 doi: 10.1088/1475-7516/2009/07/007
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15544
Deposited By: George Porter
Deposited On:14 Sep 2009 23:30
Last Modified:03 Oct 2019 00:59

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