Astrophysical interpretation of small-scale neutrino angular correlation searches with IceCube

TL;DR

This paper introduces a new method to interpret the lack of observed small-scale neutrino angular correlations in IceCube data, constraining the properties and distribution of potential astrophysical neutrino sources.

Contribution

The paper develops a novel interpretative framework linking non-observation of correlations to source population constraints, considering different astrophysical source models.

Findings

Constraints on source count distribution parameters

Limits on the number and strength of point-like sources

Implications for astrophysical neutrino source populations

Abstract

The IceCube Neutrino Observatory has discovered a diffuse all-flavor flux of high-energy astrophysical neutrinos. However, the corresponding astrophysical sources have not yet been identified. Neither significant point sources nor significant angular correlations of event directions have been observed by IceCube or other instruments to date. We present a new method to interpret the non-observation of angular correlations in terms of exclusions on the strength and number of point-like sources in generic astrophysical scenarios. Additionally, we constrain the presence of these sources taking into account the measurement of the diffuse high-energy neutrino flux by IceCube. We apply the method to two types of astrophysically motivated source count distributions: The first type is obtained by considering the cosmological evolution of the co-moving density of active galaxies, while the second type is directly derived from the gamma ray source count distribution observed by Fermi-LAT. As a result, we constrain the possible parameter space for both types of source count distributions.