Fermi Gamma-ray Space Telescope

Dark Matter Constraints from Fermi LAT measurement of the Isotropic Gamma-ray Background

Michael Gustafsson

Abstract:

The Isotropic Gamma-ray Background (IGRB) measurement by the Fermi Large Area Telescope (LAT) has recently been updated and extended up to 820 GeV. A full understanding of this IGRB is still debated and requires the identification and modeling of many possible contributions in detail. An almost isotropic signal from dark matter (DM) annihilation could account for a portion of the observed IGRB intensity, where both extragalactic DM and Galactic DM substructures induce such a signal. We refine previous estimates of the cosmological DM annihilation signal and consistently include Galactic DM contributions in an analysis to constrain DM properties from Fermi-LAT IGRB measurements. By adopting two complementary strategies to calculate the DM signal predictions, which incorporate the latest theoretical understanding of DM halos' internal structures and directly utilize the DM power spectrum from state-of-the-art N-body cosmological simulations, we decrease theoretical uncertainties and derive robust DM limits. The new limits are compared to those from observations of dwarf spheroidal galaxies and the Milky-Way halo and shown to be more constraining in some cases.