Multiwavelength Search for the Origin of IceCube's Neutrinos

Abstract The origin of astrophysical high-energy neutrinos detected by the IceCube Neutrino Observatory remains a mystery to be solved. In this paper we search for neutrino source candidates within the 90% containment area of 70 track-type neutrino events recorded by the IceCube Neutrino Observatory. By employing the Fermi-LAT 4FGL-DR2, the Swift-XRT 2SXPS, and the CRATES catalogs, we identify possible gamma-ray, X-ray, and flat-spectrum radio candidate sources of track-type neutrinos. We find that based on the brightness of sources and their spatial correlation with the track-type IceCube neutrinos, the constructed neutrino samples represent special populations of sources taken from the full Fermi-LAT 4FGL-DR2/Swift-XRT 2SXPS/CRATES catalogs with similar significance (2.1 σ , 1.2 σ , 2 σ at 4.8 GHz, 2.1 σ at 8.4 GHz, respectively, assuming 50% astrophysical signalness). After collecting redshifts and deriving subsamples of the CRATES catalog complete in the redshift–luminosity plane, we find that the 4.8 GHz (8.4 GHz) subsample can explain between 4% and 53% (3% and 42%) of the neutrinos (90% C.L.), when the probability of detecting a neutrino is proportional to the ( k -corrected) radio flux. The overfluctuations indicate that a part of the sample is likely to contribute and that more sophisticated schemes in the source catalog selection are necessary to identify the neutrino sources at the 5 σ level. Our selection serves as a starting point to further select the correct sources.