Shedding (Gamma) Light on the Cosmic Ray Population in the Galactic Center Region
2019 July 22
The nature of the very-high-energy gamma-ray diffuse emission measured by H.E.S.S. in the Galactic Center (GC) region is still matter of debate. Two main scenarios have been proposed to interpret H.E.S.S. results, where the emission arises from a cosmic-ray (CR) population, which is either originated from a local PeVatron or is the “tip of the iceberg” of an inhomogeneous Galactic CR sea. The latter scenario is motivated by recent analysis of the Galactic diffuse emission measured by Fermi-LAT as well as from Milagro and recent HAWC results. In this contribution we compare these interpretations against H.E.S.S. data in combination with updated Fermi-LAT data, which allow to extend the measured spectrum down to few GeVs. Besides the Central Molecular Zone and the Sgr B gas complex – for which we find a good agreement with data for both scenarios – here we consider, for the first time in this framework, the emission of J1741-302, under the hypothesis that is due to the interaction of CRs with a massive cloud lying on the Galactic plane at about 260 pc from the GC. We find the CR sea scenario reproduces the spectrum of J1741-302 (+ Fermi-LAT ) remarkably well, while the GC PeVatron – due to the 1/r profile of the CR density profile – falls short. Therefore, our result strongly favours the CR sea interpretation of the measured γ-ray diffuse emission from the innermost region of the Galaxy.