Dark Matter Identification with Gamma Rays from Dwarf Galaxies

Abstract

If the positron fraction and combined electron-positron flux excesses recently observed by PAMELA, FERMI and HESS are due to dark matter annihilation into lepton-rich final states, the accompanying final state radiation (FSR) photons may be detected by ground-based atmospheric Cherenkov telescopes (ACTs). Satellite dwarf galaxies in the vicinity of the Milky Way are particularly promising targets for this search. We find that current and near-future ACTs have an excellent potential for discovering the FSR photons from dwarfs, although a discovery cannot be guaranteed due to large uncertainties in the fluxes resulting from lack of precise knowledge of dark matter distribution within the dwarfs. We also investigate the possibility of discriminating between different dark matter models based on the measured FSR photon spectrum. For typical parameters, we find that the ACTs can reliably distinguish models predicting dark matter annihilation into two-lepton final states from those favoring four-lepton final states (as in, for example, "axion portal" models). In addition, we find that the dark matter particle mass can also be determined from the FSR spectrum.

25 pages, 6 figures. References added, model identification section modified, general conclusions unchanged. Final version accepted for publication in Journal of Cosmology and Astroparticle Physics

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Cited by in corpus (5)

• Gamma Ray Signals from Dark Matter: Concepts, Status and Prospects
• Fitting formulae for photon spectra from WIMP annihilation
• Photon spectra from WIMP annihilation
• Extracting limits on Dark Matter annihilation from gamma-ray observations towards dwarf spheroidal galaxies
• Decaying Dark Matter in Supersymmetric Model and Cosmic-Ray Observations