Bright gamma-ray Galactic Center excess and dark dwarfs: Strong tension for dark matter annihilation despite Milky Way halo profile

TL;DR

This study examines the Galactic Center gamma-ray excess considering uncertainties in the Milky Way's dark matter halo profile, revealing significant tension with dwarf galaxy constraints unless specific halo or local density conditions are met.

Contribution

It incorporates halo profile and diffuse emission uncertainties into dark matter models, highlighting tensions with dwarf galaxy constraints and exploring conditions to reconcile them.

Findings

Inclusion of uncertainties broadens the dark matter parameter space.

Significant tension remains between Galactic Center excess and dwarf galaxy limits.

Certain halo profiles or local density assumptions can reduce this tension.

Abstract

We incorporate Milky Way dark matter halo profile uncertainties, as well as an accounting of diffuse gamma-ray emission uncertainties in dark matter annihilation models for the Galactic Center Extended gamma-ray excess (GCE) detected by the Fermi Gamma Ray Space Telescope. The range of particle annihilation rate and masses expand when including these unknowns. However, two of the most precise empirical determinations of the Milky Way halo's local density and density profile leave the signal region to be in considerable tension with dark matter annihilation searches from combined dwarf galaxy analyses for single-channel dark matter annihilation models. The GCE and dwarf tension can be alleviated if: one, the halo is very highly concentrated or strongly contracted; two, the dark matter annihilation signal differentiates between dwarfs and the GC; or, three, local stellar density measures are found to be significantly lower, like that from recent stellar counts, increasing the local dark matter density.