Angular Signatures of Annihilating Dark Matter in the Cosmic Gamma-Ray Background

The cosmic gamma-ray background (CGB) is a very promising channel to look for signatures of dark matter annihilation. Indeed, if gamma-rays from dark matter constitute a relevant fraction of the CGB, then, together with an imprint in the energy spectrum, peculiar angular signatures are also expected. In particular, the expected anisotropies differ significantly compared to the anisotropies from emission of astrophysical sources only, provided that annihilation in sub-galactic clumps and/or in cuspy haloes gives only a moderate enhancement in the dark matter signal. In this scenario the differences are at a level detectable with the forthcoming GLAST observatory. As complementary observables we further introduce the cross-correlation between surveys of galaxies and the CGB and the cross-correlation between different energy bands of the CGB and we study their sensitivity to the dark matter angular signatures. We find that a combined analysis of all the anisotropy observables provides a powerful tool to investigate the dark matter signal.

95.85.Pw
98.70.Vc
95.35.+d
dark matter: annihilation
gamma ray: emission
gamma ray: anisotropy
gamma ray: power spectrum
cosmic background radiation
galaxy
correlation: crossing

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