Fermi Gamma-ray Space Telescope

Diffuse gamma-ray emission modeling near the Galactic Center and the 3 GeV excess

D. Malyshev
A. Franckowiak, L. Tibaldo, E. Bloom


The region near the Galactic Center (GC) is one of the most interesting and complex regions in the gamma-ray sky. Several groups have reported an excess emission in gamma rays relative to standard astrophysical components around 3 GeV. We study the systematic uncertainty of the excess emission in Pass 8 Fermi-LAT data due to modeling of astrophysical foregrounds. In particular, we test several GALPROP models of Galactic diffuse emission, develop an alternative distribution of gas along the line of sight based on starlight extinction data, model the Fermi bubbles at low latitudes, test additional sources of cosmic ray electrons near the GC, refit point sources near the GC. We find that in all models that we have tested the excess emission remains significant, the largest changes to the spectrum come from modeling of the Fermi bubbles and additional source of CR electrons.