Abstract: | The origin of astrophysical neutrinos has yet to be determined. 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 $1.64 imes 10^{-12}$ TeV cm$^{-2}$ s$^{-1}$ at 90%
confidence level. This upper limit is approximately 1% of IceCube’s diffuse
muon-neutrino flux measurement. |