Abstract
The extended excess toward the Galactic Center (GC) in gamma rays inferred from Fermi-LAT observations has been interpreted as being due to dark matter (DM) annihilation. Here, we perform new likelihood analyses of the GC and show that, when including templates for the stellar galactic and nuclear bulges, the GC shows no significant detection of a DM annihilation template, even after generous variations in the Galactic diffuse emission models and a wide range of DM halo profiles. We include Galactic diffuse emission models with combinations of three-dimensional inverse Compton maps, variations of interstellar gas maps, and a central source of electrons. For the DM profile, we include both spherical and ellipsoidal DM morphologies and a range of radial profiles from steep cusps to kiloparsec-sized cores, motivated in part by hydrodynamical simulations. Our derived upper limits on the dark matter annihilation flux place strong constraints on DM properties. In the case of the pure $b$-quark annihilation channel, our limits on the annihilation cross section are more stringent than those from the Milky Way dwarfs up to DM masses of approximately TeV and rule out the thermal relic cross section up to approximately 300 GeV. Better understanding of the DM profile, as well as the Fermi-LAT data at its highest energies, would further improve the sensitivity to DM properties.
Highlights
The particle nature of dark matter (DM) remains one of the most important unresolved questions in astrophysics, cosmology, and particle physics
We find that an emission template that traces stellar mass in the Galactic bulge is preferred in all energy bins over each of the DM templates considered in this analysis
With detected sources that are consistent with the Fermi bubbles; 4FGL point sources; detailed inverse Compton (IC) emission maps; disk gas; and, most importantly, the emission from the stellar Galactic bulge and nuclear bulge, there is no significant excess in the Galactic Center (GC) that may be attributed to DM annihilation
Summary
The particle nature of dark matter (DM) remains one of the most important unresolved questions in astrophysics, cosmology, and particle physics. After the launch of the Fermi Gamma-Ray Space Telescope, an extended source of gamma ray emission was quickly identified toward the GC and shown to be consistent with the annihilation of thermal weak-interactionscale DM producing gamma rays [6] This GC excess (GCE) has since been detected by many follow-up analyses, which indicated its potential association with. Part of the GCE signal could be explained by gamma-ray emission induced by cosmic rays injected by ongoing star formation activity in the GC region [12], cosmic-ray bremsstrahlung off of molecular gas [8], or inverse-Compton emission from leptonic cosmic rays [13,14] These studies are not able to completely explain the data, and still leave the need for a spherical GCE. For two-body final states with hadronic components, we are able to rule out thermal DM up to approximately 300 GeV in mass, surpassing the reach from dwarf satellites of the MW for DM particles with masses less than a TeV
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