Dominant sources of the diffuse astrophysical neutrino flux

Determine the nature and identity of the astrophysical source populations that dominate the observed diffuse astrophysical neutrino flux, in order to establish which classes of objects are primarily responsible for the bulk of the high-energy neutrino emission detected by neutrino telescopes.

Background

High-energy astrophysical neutrinos have been detected, confirming the existence of a diffuse neutrino flux of cosmic origin. However, the specific source classes and mechanisms that generate the majority of this flux are not yet established. Candidate populations include blazars and other active galactic nuclei among others, but a definitive attribution remains unresolved.

This paper investigates potential blazar counterparts for the ultra-high-energy event KM3-230213A, reflecting broader efforts to connect individual neutrino detections to source classes. Despite suggestive multiwavelength variability in several candidates, no conclusive association is demonstrated, underscoring the broader open problem of identifying the dominant contributors to the diffuse neutrino background.