Galactic Diffuse Neutrino Emission from Sources beyond the Discovery Horizon

TL;DR

This paper explores whether unresolved Galactic sources, especially young stellar clusters, could dominate the diffuse neutrino emission observed by IceCube, and assesses how future detectors might test this hypothesis.

Contribution

It introduces the idea that unresolved sources may significantly contribute to the Galactic neutrino flux and evaluates future detector capabilities to test this hypothesis.

Findings

Unresolved sources could dominate the diffuse neutrino flux at 100 TeV.

Young stellar clusters are promising candidate sources.

Future detectors like KM3NeT and IceCube-Gen2 can test this hypothesis.

Abstract

The IceCube Neutrino Observatory has recently reported strong evidence for neutrino emission from the Galactic plane. The signal is consistent with model predictions of diffuse emission from cosmic ray propagation in the interstellar medium. However, due to IceCube's limited potential of identifying individual neutrino sources, it is also feasible that unresolved Galactic sources could contribute to the signal. We investigate the contribution of this quasi-diffuse emission and show that the observed Galactic diffuse flux at 100 TeV could be dominated by hard emission of unresolved sources. Particularly interesting candidate sources are young massive stellar clusters that have been considered as cosmic-ray PeVatrons. We examine whether this hypothesis can be tested by the upcoming KM3NeT detector or the planned future facility IceCube-Gen2 with about five times the sensitivity of IceCube.