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Challenges in Revealing Dark Matter from the High Energy Gamma-Ray Background (Continuum). Ranga-Ram Chary Spitzer Science Center, Caltech rchary@caltech.edu. The Different Galactic Components. GALACTIC PLANE l~0, b~0. GALACTIC ANTICENTER l~180, b~75. Isotropic Component.
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Challenges in Revealing Dark Matter from the High Energy Gamma-Ray Background (Continuum) Ranga-Ram Chary Spitzer Science Center, Caltech rchary@caltech.edu
The Different Galactic Components GALACTIC PLANE l~0, b~0 GALACTIC ANTICENTER l~180, b~75 Isotropic Component p-p component EB component IC Component Gas Scale Height is smaller than Radiation Field Scale Height Hunter et al., Bertsch et al.
Contribution of Dark Matter to the E~150 MeV Background Strong Dependence on Emissivity and Halo Core Radius
Current Constraints on the Spectrum of the Residual Halo Emission: Looks more like γ-raypulsars Isotropic EBL ~ E-2.1 Anisotropic Halo Component ~ E-1.7
The Radiation Field R=5 kpc, z=0 kpc R=5 kpc, z=1.5 kpc R=8.5 kpc, z=1.5 kpc The Radial Scale Length of the ISRF Energy Density is ~3 kpc The Scale Height is ~1.5 kpc In contrast, gas Scale Height is ~100 pc
A Visual Approach Although the average intensity is the same, anisotropy is x10-100 greater on the right
Uncertainty II: The Cosmic Ray Spectrum and Intensity - Strong Dependence on Distance from SNR R=5 kpc, z=0 kpc R=5 kpc, z=1.5 kpc R=8.5 kpc, z=1.5 kpc
The Problem List For our galaxy: • CR propagation model (Can it be done ?) • Azimuthal angle dependent ISRF using more recent Sloan, Spitzer and 2MASS data To Pinpoint Dark Matter Consider: • Deep GLAST pointings at edge on galaxies – still need to remove the IC component • Of course, dwarf galaxies and clusters might remain the best place to identify dark matter • Angular power spectrum of CGRB is likely to be dominated by unresolved blazars