Radio astronomy locates the neutrino origin in bright blazars

TL;DR

This study statistically links bright radio blazars to high-energy astrophysical neutrinos, identifying specific sources and demonstrating that blazars could account for a significant portion of the neutrino flux observed by IceCube.

Contribution

It provides the first statistical evidence connecting radio-bright blazars with neutrino detections and shows that neutrino production occurs in relativistic jets of AGNs.

Findings

Strong positional correlation between blazars and neutrino detections (4.1 sigma significance).

Identification of four highly probable neutrino sources: 3C 279, NRAO 530, PKS 1741-038, PKS 2145+067.

Radio flares above 10 GHz coincide with neutrino arrival dates, indicating a link between jet activity and neutrino emission.

Abstract

High-energy astrophysical neutrinos have been observed by several telescopes in the last decade, but their sources still remained unknown. We address the problem of locating astrophysical neutrinos' sources in a statistical manner. We show that blazars positionally associated with IceCube neutrino detections have stronger parsec-scale radio cores than the rest of the sample. The probability of a chance coincidence is only 4*10^-5 corresponding to a significance of 4.1 sigma. We explicitly list four strong radio blazars as highly probable sources of neutrinos above 200 TeV: 3C 279, NRAO 530, PKS 1741-038, and PKS 2145+067. There are at least 70 more radio-bright blazars that emit neutrinos of lower energies, starting from TeVs. Using continuous RATAN-600 monitoring of VLBI-selected blazars, we find that radio flares at frequencies above 10 GHz coincide with neutrino arrival dates. The most pronounced example of such behavior is PKS 1502+106 that experienced a major flare in 2019. We demonstrate that the majority of IceCube astrophysical neutrino flux derived from muon-track analyses may be explained by blazars, that is, AGNs with bright Doppler-boosted jets. High-energy neutrinos can be produced in photohadronic interactions within parsec-scale relativistic jets. Radio-bright blazars associated with neutrino detections have very diverse gamma-ray properties, which suggests that gamma-rays and neutrinos may be produced in different regions of blazars and not directly related. A narrow jet viewing angle is, however, required to detect either of them. We conclude with discussion of recent independent tests and extensions of our findings.