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. http://resolver.caltech.edu/CaltechAUTHORS:20090901-161606701
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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.
|Additional Information:||Copyright © 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|
|Subject Keywords:||dark matter; structure of galaxies|
|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.|
|Deposited By:||George Porter|
|Deposited On:||14 Sep 2009 23:30|
|Last Modified:||15 Jan 2015 20:47|
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