Multimessenger study of the Galactic diffuse emission with LHAASO and IceCube observations

With the breakthrough in PeV gamma-ray astronomy brought about by the LHAASO experiment, the high-energy sky is becoming richer. Recently, the LHAASO Collaboration reported the observation of a gamma-ray diffuse emission with energy up to the PeV level from both the inner and outer Galactic plane. In these spectra, there is a bump that is hard to explain using the conventional cosmic-ray transport scenarios. Therefore, we introduce two extra components corresponding to unresolved sources with exponential-cutoff-power-law (ECPL) spectral shape---one with an index of 2.4 and cutoff energy of 20 TeV, and another with an index of 2.3 and cutoff energy of 2 PeV. With our constructed model, we simulate the Galactic diffuse neutrino flux and find that our results are in full agreement with the latest IceCube Galactic plane search. We estimate the Galactic neutrino contributes $\ensuremath{\sim}9%$ of astrophysical neutrinos at 20 TeV. In the high-energy regime, as expected, most of the neutrinos observed by IceCube should be from extragalactic environments.