Strong Lensing of High-Energy Neutrinos

TL;DR

This paper studies how strong gravitational lensing by galaxies affects the observation of high-energy neutrinos, predicting rare multiple images and providing tools to identify such events in future experiments.

Contribution

It analyzes the probability and observable effects of strong lensing on high-energy neutrinos, including time delays and impacts on flux and source counts.

Findings

Optical depth for multiple imaging is ~10^-3 for cosmological HEN.

Next-generation detectors may observe multiply imaged neutrinos.

Lensing effects on the cosmic neutrino background are negligible.

Abstract

We consider the effects of strong gravitational lensing by galaxy-scale deflectors on the observations of high-energy (E$\gg$GeV) neutrinos (HEN). For HEN at cosmological distances, the optical depth for multiple imaging is $\sim 10^{-3}$, implying that while we do not expect any multiply imaged HEN with present samples, next-generation experiments should be able to detect the first such event. We then present the distribution of expected time delays to aid in the identification of such events, in combination with directional and energy information. In order to assist in the evaluation of HEN production mechanisms, we illustrate how lensing affects the observed number counts for a variety of intrinsic luminosity functions of the source population. Finally, we see that the lensing effects on the cosmic neutrino background flux calculation would be negligible by taking kpc-scale jets as an example.