Constraints on Extragalactic Point Source Flux from Diffuse Neutrino Limits

TL;DR

This paper establishes upper limits on the flux from extragalactic neutrino point sources using diffuse neutrino flux constraints, revealing that these sources are less luminous than current detection thresholds and constraining their population and power density.

Contribution

It provides a novel method to constrain extragalactic neutrino source fluxes and densities based on diffuse neutrino flux limits, with minimal dependence on source distribution assumptions.

Findings

Maximum flux from extragalactic sources is below current experimental limits.

Constraints on source number density and total neutrino power density.

Flux limits are only slightly affected by local universe matter distribution.

Abstract

We constrain the maximum flux from extragalactic neutrino point sources by using diffuse neutrino flux limits. We show that the maximum flux from extragalactic point sources is E^2(dN/dE) < 1.4 x 10^-9 (L_nu/2x10^43 erg/s)^1/3 GeV cm-^2 s^-1 from individual point sources with average neutrino luminosity per decade, L_nu. It depends only slightly on factors such as the inhomogeneous matter density distribution in the local universe, the luminosity distribution, and the assumed spectral index. The derived constraints are at least one order of magnitude below the current experimental limits from direct searches. Significant constraints are also derived on the number density of neutrino sources and on the total neutrino power density.