The gamma-ray-flux PDF from galactic halo substructure
Abstract
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
© 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.Attached Files
Submitted - 0810.1284v2.pdf
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Additional details
- Eprint ID
- 15544
- Resolver ID
- CaltechAUTHORS:20090901-161606701
- Sherman Fairchild Foundation
- DE-FG03-92-ER40701
- Department of Energy (DOE)
- Gordon and Betty Moore Foundation
- Created
-
2009-09-14Created from EPrint's datestamp field
- Updated
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2022-07-12Created from EPrint's last_modified field
- Caltech groups
- TAPIR, Moore Center for Theoretical Cosmology and Physics