On the "GeV excess" in the diffuse γ-ray emission towards the Galactic Center

Rui-zhi Yang, Felix Aharonian

Published 2016-02-22Version 1

The Fermi \gamma -ray data have been used to study the morphological and spectral features of the so-called "GeV excess" - a diffuse radiation component recently discovered toward the Galactic Center. Our independent study does confirm the existence of such an extra component in the diffuse \gamma -ray emission at GeV energies. Based on a detailed morphological analysis, a spatial template that fits best the data, has been generated and adopted. Using this template, the energy distribution of \gamma -rays was derived in the 0.3-30 GeV energy interval. The spectrum appeared to have less distinct ("bump"-like) structure compared to the previous reports. We argue that the morphology of this radiation component has a bipolar rather than spherically symmetric structure as it has been a priori assumed in previous studies. This finding excludes the associations of the "GeV excess" with Dark Matter. We briefly discuss the radiation mechanisms and possible source populations which could be responsible for this new component of diffuse gamma-radiation.