Strong constraints on thermal relic dark matter from Fermi-LAT observations of the Galactic Center

The extended excess toward the Galactic Center (GC) in gamma raysinferred from Fermi-LAT observations has been interpreted as being dueto dark matter (DM) annihilation. Here, we perform new likelihoodanalyses of the GC and show that, when including templates for thestellar galactic and nuclear bulges, the GC shows no significantdetection of a DM annihilation template, even after generous variationsin the Galactic diffuse emission models and a wide range of DM haloprofiles. We include Galactic diffuse emission models with combinationsof three-dimensional inverse Compton maps, variations of interstellargas maps, and a central source of electrons. For the DM profile, weinclude both spherical and ellipsoidal DM morphologies and a range ofradial profiles from steep cusps to kiloparsec-sized cores, motivated inpart by hydrodynamical simulations. Our derived upper limits on the darkmatter annihilation flux place strong constraints on DM properties. Inthe case of the pure b-quark annihilation channel, our limits on theannihilation cross section are more stringent than those from the MilkyWay dwarfs up to DM masses of approximately TeV and rule out the thermalrelic cross section up to approximately 300 GeV. Better understanding ofthe DM profile, as well as the Fermi-LAT data at its highest energies,would further improve the sensitivity to DM properties.