Multiwavelength Search for the Origin of IceCube's Neutrinos

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 (2.1σ, 1.2σ, 2σ at 4.8 GHz, 2.1σ 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 5σ level. Our selection serves as a starting point to further select the correct sources