Investigating the correlations between IceCube high-energy neutrinos and Fermi-LAT $\gamma$-ray observations. II

TL;DR

This study explores the correlation between high-energy neutrinos detected by IceCube and gamma-ray sources observed by Fermi-LAT, aiming to identify potential neutrino sources and understand their contribution to the diffuse neutrino flux.

Contribution

It introduces an analysis of spatial correlations between neutrino hotspots and gamma-ray source catalogs using IceCube's p-value sky map, extending previous work with new statistical methods.

Findings

Possible correlation between neutrino hotspots and the 3FHL gamma-ray source catalog.

The correlation is mainly driven by three known sources: NGC 1068, TXS 0506+056, and PKS 1424+240.

Post-trial significance of the correlation is approximately 1.7 sigma.

Abstract

Given that gamma rays with energies larger than TeV are severely absorbed by background radiation fields, for many extragalactic sources, the GeV-TeV gamma-ray observations are the messengers that are closest in energy to the TeV-PeV neutrinos observed by IceCube. Investigating whether there is a correlation between the gamma-ray and neutrino observations can help us identify high-energy neutrino sources and determine which sources are the main contributors to the all-sky diffuse neutrino flux of IceCube. In previous work, we have already studied the possible gamma-neutrino correlations by analyzing 10 years of IceCube public muon-track data. In this work, we further investigate such correlations by employing the IceCube p-value sky map of the scan for point sources. We examine the spatial associations of hotspots in the neutrino sky map with various gamma-ray source samples: the third Fermi-LAT catalog of high-energy sources (3FHL), LAT 14-year source catalog (4FGL), the fourth catalog of active galactic nuclei (4LAC) and subsets of these samples. Among all the samples, the 3FHL sample shows a possible correlation with the neutrino hotspots with a pre-trial p-value of $9.0\times10^{-5}$ ($\sim 3.9\,\sigma$), corresponding to a post-trial significance of $\sim1.7\,\sigma$. However, this is found to be caused by three already known neutrino sources/source candidates: NGC 1068, TXS 0506+056, and PKS 1424+240.