What IceCube data tell us about neutrino emission from star-forming galaxies (so far)

TL;DR

IceCube neutrino data suggests a possible link to star-forming galaxies, and future observations with improved resolution could confirm this connection, advancing understanding of astrophysical neutrino sources.

Contribution

This study analyzes IceCube data to explore the potential association between high-energy neutrinos and star-forming galaxies, proposing methods for future confirmation with upgraded detectors.

Findings

Current neutrino flux aligns with starburst galaxy expectations.

High-energy events have large angular uncertainties, limiting definitive associations.

Upgraded IceCube could statistically confirm or refute the galaxy-neutrino link within a few years.

Abstract

Very recently, the IceCube Collaboration reported a flux of neutrinos in the energy range 50 TeV < E_\nu < 2 PeV, which departs from expectations from atmospheric background at the 5.7\sigma level. This flux is in remarkable agreement with the expected diffuse flux of neutrinos from starburst galaxies, and the 3 highest energy events have uncertainty contours encompassing some of such systems. These events, all of which have well-measured energies above 1 PeV, exhibit shower topologies, for which the angular resolution is about 15^\circ. Due to this angular uncertainty and the a posteriori nature of cuts used in our study it is not possible to assign a robust statistical significance to this association. Using muon tracks, which have angular resolution < 1^\circ, we compute the number of observations required to make a statistically significant statement, and show that in a few years of operation the upgraded IceCube detector should be able to confirm or refute this hypothesis. We also note that double bang topology rates constitute a possible discriminator among various astrophysical sources.