Search for Astrophysical Neutrinos from 1FLE Blazars with IceCube

TL;DR

This study conducted a decade-long search for neutrino emissions from MeV-detected blazars using IceCube data, finding no significant signals but setting upper limits on their neutrino fluxes, which are about 1% of the diffuse flux.

Contribution

First time-integrated stacking analysis of MeV-detected blazars for neutrino emission using ten years of IceCube data, providing new upper limits on their neutrino flux.

Findings

No significant neutrino excess detected from 1FLE blazars.

Upper limit on neutrino flux is 1.64 x 10^{-12} TeV cm^{-2} s^{-1}.

Upper limit is about 1% of IceCube's diffuse neutrino flux.

Abstract

The majority of astrophysical neutrinos have undetermined origins. The IceCube Neutrino Observatory has observed astrophysical neutrinos but has not yet identified their sources. Blazars are promising source candidates, but previous searches for neutrino emission from populations of blazars detected in $\gtrsim$ GeV gamma-rays have not observed any significant neutrino excess. Recent findings in multi-messenger astronomy indicate that high-energy photons, co-produced with high-energy neutrinos, are likely to be absorbed and reemitted at lower energies. Thus, lower-energy photons may be better indicators of TeV-PeV neutrino production. This paper presents the first time-integrated stacking search for astrophysical neutrino emission from MeV-detected blazars in the first Fermi-LAT low energy catalog (1FLE) using ten years of IceCube muon-neutrino data. The results of this analysis are found to be consistent with a background-only hypothesis. Assuming an E$^{-2}$ neutrino spectrum and proportionality between the blazars' MeV gamma-ray fluxes and TeV-PeV neutrino flux, the upper limit on the 1FLE blazar energy-scaled neutrino flux is determined to be $1.64 \times 10^{-12}$ TeV cm$^{-2}$ s$^{-1}$ at 90% confidence level. This upper limit is approximately 1% of IceCube's diffuse muon-neutrino flux measurement.