Anisotropies in the Diffuse Gamma-Ray Background from Dark Matter with Fermi LAT: a closer look

TL;DR

This study analyzes the sensitivity of Fermi-LAT to gamma-ray anisotropies caused by dark matter, considering Galactic and extragalactic sources, and finds that anisotropy measurements can effectively complement spectral methods in dark matter detection.

Contribution

First detailed analysis incorporating Galactic foregrounds and realistic Fermi-LAT modeling to assess dark matter anisotropies in gamma-ray background.

Findings

Fermi-LAT can detect dark matter signals at the thermal relic cross section level.

Anisotropy method provides sensitivity comparable to spectral analysis.

Results depend on dark matter mass and annihilation mode.

Abstract

We perform a detailed study of the sensitivity to the anisotropies related to Dark Matter (DM) annihilation in the Isotropic Gamma-Ray Background (IGRB) as measured by the Fermi Large Area Telescope (Fermi-LAT). For the first time, we take into account the effects of the Galactic foregrounds and use a realistic representation of the Fermi-LAT. We consider DM anisotropies of extra-galactic origin and of Galactic origin (which can be generated through annihilation in the Milky Way sub-structures) as opposed to a background of anisotropies generated by sources of astrophysical origin, blazars for example. We find that with statistics from 5 years of observation Fermi is sensitive to a DM contribution at the level of the thermal-relic cross section depending on the DM mass and annihilation mode. The anisotropy method for DM searches has a sensitivity comparable to the usual methods based only on the energy spectrum and thus constitutes an independent and complementary piece of information in the DM puzzle. (abridged)