Hadronic nature of high-energy emission from the Galactic ridge

We show that the IceCube observation of the Galactic neutrino-flux component confirms the hint of detection of neutrinos from the Galactic ridge (the inner part of the Milky Way disk within the Galactic longitude IlI < 30(degrees)), previously reported by the ANTARES Collaboration. This confirmation indicates that the bulk of the high-energy flux from the Galactic ridge in multi-TeV band is produced by interactions of high-energy protons and atomic nuclei, rather than electrons. We show that both ANTARES and IceCube measurements agree with the Fermi-LAT telescope measurements of the gamma-ray emission from the ridge. The multimessenger (neutrino plus gamma-ray) spectrum of the ridge over a broad energy range from 10 GeV to 10 TeV is consistent with a model of pion decay emission produced by a power-law distribution of protons with a slope Gamma similar or equal to 2.5, harder than that of the locally observed cosmic ray spectrum. This provides a multimessenger demonstration of the variability of the spectrum of cosmic rays across the Galactic disk.