NBIA Seminar: Dmitry Malyshev

(FAU Erlangen)

Analysis of the 3 GeV gamma-ray excess near the Galactic center with Fermi LAT data

Gamma-ray emission from dark matter (DM) annihilation is expected to be brightest toward the Galactic center (GC). Several groups have reported an excess of gamma-ray emission toward the GC with an approximately spherical shape and a spectral energy distribution peaking around a few GeV. In the talk, I will describe the current observational status of the GC excess and review possible explanations. I will present the latest analysis of the Fermi LAT gamma-ray data near the Galactic center. To test the robustness of the GC excess, we derive different models of Galactic diffuse gamma-ray emission by varying the distribution of cosmic ray sources, CR propagation, and gas distribution. We also develop a model of the Fermi bubbles at low latitudes and add extra sources of cosmic rays near the GC. We find that the GC excess remains significant in all models that we have tested. The size of this excess relative to the background is similar to the fractional residuals found at other locations along the Galactic plane. As a result, we cannot claim that the GC excess is due to DM annihilation and so we derive limits on annihilating dark matter.