Gamma-ray and Neutrino Diffuse Emissions of the Galaxy at very High Energy

Abstract

Several independent analyzes of Fermi-LAT results found evidences of a spatial dependent cosmic ray (CR) spectral index which is not accounted for by conventional models of CR transport in the Galaxy. Moreover, several experiments have established the presence of a CR spectral hardening above few hundred GeV. We show that these results may have a relevant impact on the γ-ray and neutrino diffuse emissions of the Galaxy above the TeV. Indeed a phenomenological model which adopts a spatial dependent diffusion coefficient, so to account for those features, also reproduces the γ-ray excess found by Milagro at 15 TeV and the spectrum measured by H.E.S.S. and Fermi-LAT in the Galactic ridge. The same model predicts a neutrino emission along the Galactic plane which is significantly larger than expected on the basis of conventional models. This emission is compatible with ANTARES upper limits and is a natural target for KM3NeT.