Angular Signatures of Dark Matter in the Diffuse Gamma Ray Background

Abstract

Dark matter annihilating in our Galaxy's halo and elsewhere in the universe is expected to generate a diffuse flux of gamma rays, potentially observable with next generation satellite-based experiments, such as GLAST. In this article, we study the signatures of dark matter in the angular distribution of this radiation, in particular the deterministic ones. Pertaining to the extragalactic contribution, we discuss the effect of the motion of the solar system with respect to the cosmological rest frame, and anisotropies due to the structure of our local universe. For the gamma ray flux from dark matter in our own Galactic halo, we discuss the effects of the offset position of the solar system, the Compton-Getting effect, the asphericity of the Milky Way halo, and the signatures of nearby substructure. We explore the prospects for the detection of these features by the GLAST satellite and find that, if ~10% or more of the diffuse gamma ray background observed by EGRET is the result of dark matter annihilations, then GLAST should be sensitive to anisotropies at the sub-percent level. Such precision would be sufficient to detect many, if not all, of the signatures discussed in this paper.

13 pages, 5 figures; minor adjustments, clarifications added, conclusions unchanged; matches published version

References in corpus (6)

• Baryonic Pinching of Galactic Dark Matter Halos
• The survival and disruption of CDM micro-haloes: implications for direct and indirect detection experiments
• Can Dark Matter Annihilation Dominate the Extragalactic Gamma-Ray Background?
• Challenges in Detecting Gamma-Rays From Dark Matter Annihilations in the Galactic Center
• Proper motion of gamma-rays from microhalo sources
• The Compton-Getting effect on ultra-high energy cosmic rays of cosmological origin

Cited by in corpus (7)

• Neutrino Constraints on the Dark Matter Total Annihilation Cross Section
• The fine-grained phase-space structure of Cold Dark Matter halos
• Model-independent dark matter annihilation bound from the diffuse gamma ray flux
• The Gamma-Ray-Flux Probability Distribution Function from Galactic Halo Substructure
• Extracting the Gamma Ray Signal from Dark Matter Annihilation in the Galactic Center Region
• Angular Signatures of Annihilating Dark Matter in the Cosmic Gamma-Ray Background
• Determining the WIMP mass using the complementarity between direct and indirect searches and the ILC