Probing particle dark matter with gamma-ray background anisotropy

Shin’ichiro Ando

December 07, 2009

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Abstract: Weakly interacting massive particle (WIMP) is one of the most fascinating candidates of dark matter. If WIMP is dark matter, then it might self-annihilate to yield gamma-ray signatures from dense regions of dark-matter halos. Such gamma rays will also contribute to the diffuse gamma-ray background at some level. Recently launched Fermi telescope will observe the gamma-ray background by measuring not only energy spectrum but also angular power spectrum. I show that the dark matter annihilation will imprint characteristic angular signature on the gamma-ray background, depending on if the signal is coming from extragalactic halos or Galactic subhalos. I then compare the results with the case of astrophysical point sources such as blazars, and show that the dark-matter component could be discriminated from astrophysical “backgrounds”. I conclude that the angular power spectrum could be one of the most powerful probes of particle dark matter.