Resolving the Galactic Center Region's Gamma-Ray Emission and Searching for its Neutrino Counterpart with HAWC and IceCube

Abstract

The Galactic Center (GC) is a prime candidate for petaelectronvolt cosmic-ray acceleration, with gamma-ray emission observed by the High Altitude Water Cherenkov (HAWC) Observatory extending beyond 100~TeV. Using $\sim$2860 days of HAWC data with improved machine-learning gamma/hadron separation, we present the first spatially resolved model of the GC region at the highest gamma-ray energies. The emission is resolved into a point source, HAWC J1745-2857, and a Galactic diffuse emission component that was not significant in previous HAWC analyses. With the diffuse emission accounted for, the point-source spectrum extends beyond 100~TeV with no evidence of a cutoff, showing that the PeVatron interpretation of the GC does not arise from unresolved diffuse emission. Assuming a hadronic origin, we construct the corresponding neutrino signal template and search for it in 12 years of IceCube muon-track data. No significant neutrino excess is found, and we report the first upper limit on the high-energy neutrino flux associated with the multi-component spatial model of the GC derived from HAWC data. The limit is approximately 12 times the nominal neutrino flux predicted from the HAWC gamma-ray model under a hadronic interpretation. Although the limit does not yet test the optically thin hadronic scenario, it quantifies the sensitivity required to test the hadronic origin of the GC PeVatron with future neutrino observations.

arXiv commentAccepted for publication in ApJ Letters