Fermi-LAT counterparts of IceCube neutrinos above 100 TeV

TL;DR

This study investigates the potential association between Fermi-LAT detected blazars and IceCube neutrinos above 100 TeV, finding no direct correlation but consistent neutrino flux estimates with observations.

Contribution

It extends previous analyses to include all HESE neutrinos above 100 TeV and constrains the neutrino flux from blazars using a larger sample, improving understanding of their role in high-energy neutrino production.

Findings

Neutrino flux estimates align with IceCube observations.

No direct correlation between gamma-ray flux and neutrino flux.

Expected neutrino counts are consistent with non-detection of bright blazars.

Abstract

The IceCube Collaboration has published four years of data and the observed neutrino flux is significantly in excess of the expected atmospheric background. Due to the steeply falling atmospheric background spectrum, events at the highest energies are most likely extraterrestrial. In our previous approach we have studied blazars as the possible origin of the High-Energy Starting Events (HESE) neutrino events at PeV energies. In this work we extend our study to include all HESE neutrinos (which does not include IC 170922A) at or above a reconstructed energy of 100 TeV, but below 1 PeV. We study the X-ray and $\gamma$-ray data of all ($\sim200$) 3LAC blazars that are positionally consistent with the neutrino events above 100 TeV to determine the maximum neutrino flux from these sources. This larger sample allows us to better constrain the scaling factor between the observed and maximum number of neutrino events. We find that when we consider a realistic neutrino spectrum and other factors, the number of neutrinos is in good agreement with the detected number of IceCube HESE events. We also show that there is no direct correlation between \Fermi-LAT $\gamma$-ray flux and the IceCube neutrino flux and that the expected number of neutrinos is consistent with the non-detection of individual bright blazars.