Fermi Gamma-ray Space Telescope

Fear not! Observational status and interpretations of the Galactic center GeV excess

C. Weniger


The diffuse gamma-ray emission from the inner Galaxy provides a spectacular and unique window into the complex dynamics of the Galactic bulge and center. Processes like star formation or the past activity of the central supermassive black hole can enrich the Galactic bulge with high-energetic cosmic rays that give rise to inverse Compton emission. A bulge population of e.g. millisecond pulsars can generate observable quasi-diffuse gamma-ray emission before these sources would be detectable at any other wavelength. And the most popular models for dark matter predict significant amounts of gamma rays from dark matter self-annihilation in the Galactic center. In this talk, I will summarize the observational status of the ``Fermi GeV excess'', a rather extended excess emission at GeV energies that has been found in the inner 10 degrees or so of the Galactic center, on top of conventional models for the Galactic diffuse emission. After addressing the simple question ``an excess above what?'', I will summarize the various proposed interpretations, present supportive evidence for the millisecond pulsar hypothesis, and provide an outlook on how progress can be made in the upcoming years.