High energy emission from the center of our Galaxy

Employing data collected during the first 25 months observations by the Fermi-LAT, we describe and subsequently seek to model the very-high energy (> 300 MeV) emission from the central few parsecs of our Galaxy. Using the combination of Fermi data on 1FGL J1745.6-2900 and HESS data on the coincident, TeV source HESS J1745-290, we show that the spectrum of the central gamma-ray source is flat at both low and high energies with a relatively steep spectral region inbetween. We model the gamma-ray production in the inner 10 pc of the Galaxy and examine cosmic ray (CR) proton propagation scenarios that reproduce the observed spectrum of the central source. We show that a model considering a transition from diffusive propagation of the CR protons at low energy to almost rectilinear propagation at high energies can well explain the spectral phenomenology. We find considerable degeneracy between different parameter choices which will only be broken with the addition of morphological information that gamma-ray telescopes cannot deliver given current angular resolution limits. We argue that a future analysis performed in combination with higher-resolution radio continuum data holds out the promise of breaking this degeneracy.