Time-Integrated Searches for Sub-TeV Neutrino Sources with IceCube-DeepCore

Abstract

We have developed techniques for a competitive sub-TeV time-integrated neutrino search and applied it to 11.1 years of IceCube-DeepCore data. The DeepCore subarray lowers the sensitivity of IceCube down to sub-TeV energies and is especially interesting for objects with soft spectra. Three studies were performed: a search for neutrino emission from AGN exhibiting high intrinsic X-ray flux, including NGC 1068, as identified by SWIFT/BAT; a search for neutrino emission from Galactic objects identified by Fermi-LAT as exhibiting a spectral shape consistent with neutral pion decay; and an all-sky search for neutrino point sources. Objects for this study were selected given their prospects for sub-TeV neutrino emission. No evidence for sub-TeV neutrino emission is found in any of the searches performed. Finally, for each catalog of objects, we use a statistical combination of the p-values via a binomial test to search for aggregated neutrino emission from a subset of the objects. Neither of the binomial tests yields significant results. For NGC 1068, assuming a power law spectrum with index 3.4, the 90% confidence level upper limit on per-flavor neutrino emission in the 30--400 GeV range is ${\Phi }_{\nu +\bar{\nu }}{|}_{1TeV}<9.5\times 10^{-11}$ TeV${}^{-1}$ cm${}^{-2}$ s${}^{-1}$, a factor of two higher than the extrapolation of IceCube's measurement at higher energies. We additionally provide neutrino flux upper limits for a variety of spectra.