Constraining Dwarf Spheroidal Dark Matter Halos With The Galactic Center Excess

Abstract

If the gamma-ray excess from the galactic center reported by Fermi-LAT is a signal from annihilating dark matter, one must question why a similar excess has not been observed in dwarf spheroidal galaxies. We use this observation to place constraints on the density profile of dwarf spheroidal galaxies under the assumption that the galactic center excess is in fact a signal from annihilating dark matter. We place constraints on the generalized NFW parameter $\gamma$ and the Einasto profile parameter $\alpha$ which control the logarithmic slope of the inner regions of the halo's density profile. We determine that under these assumptions the galactic center excess is inconsistent with the standard NFW profile (and other `cuspy' profiles) for dwarf spheroidal galaxies , but is consistent with observations of cored dwarf galaxy profiles. Specifically, we find that dwarf spheroidal profiles must be less cuspy than that of the Milky Way. Models of dark matter which self-interacts through a light mediator can achieve this.Comment: 8 pages, 5 figure