Multi-messenger Study of Galactic Diffuse Emission with LHAASO and IceCube Observations

TL;DR

This study models Galactic diffuse gamma-ray and neutrino emissions using LHAASO and IceCube data, introducing new source components to explain PeV observations and estimating their contribution to neutrino flux.

Contribution

It presents a novel model incorporating unresolved sources with exponential-cutoff-power-law spectra to explain PeV gamma-ray emission and neutrino flux from the Galaxy.

Findings

Galactic diffuse gamma-ray emission up to PeV energies observed by LHAASO.

Constructed model matches IceCube Galactic plane neutrino observations.

Galactic neutrinos contribute about 9% of astrophysical neutrinos at 20 TeV.

Abstract

With the breakthrough in PeV gamma-ray astronomy brought by the LHAASO experiment, the high-energy sky is getting richer than before. Lately, 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 one bump that is hard to explain by 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 20 TeV cutoff energy, and another with index of 2.3 and 2 PeV cutoff energy. With our constructed model, we simulate the Galactic diffuse neutrino flux and find our results are in full agreement with the latest IceCube Galactic plane search. We estimate the Galactic neutrino contributes of $\sim 9\%$ 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.