High-energy neutrinos from blazars

¹ Julius-Maximilians-Universität Würzburg, Fakultät für Physik und Astronomie, Würzburg, Germany
² Deutsches Elektronen-Synchrotron DESY, Zeuthen, Germany
³ Dipartimento di Fisica e Astronomia (DIFA), Università di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy

^* e-mail: sara.buson@uni-wuerzburg.de

Published online: 6 March 2025

Abstract

Identifying the origin of the majority of high-energy cosmic neutrinos observed by the IceCube Neutrino Observatory remains a significant challenge. Previous studies reported evidence of a spatial correlation between blazars listed in the 5th Roma-BZCat catalog and IceCube neutrino data in the southern celestial hemisphere. The statistical significance of this correlation was determined to be 2 × 10⁻⁶ after accounting for trials. In subsequent work, we investigated whether a similar correlation exists in the northern hemisphere, where IceCube predominantly detects neutrinos with energies ≲ 0.1 PeV. Our analysis reveals a consistent correlation between blazars and neutrino data in the northern hemisphere, with a pre-trial p-value of 5.12 × 10⁻⁴ and a post-trial chance probability of 6.79 × 10⁻³. By combining the post-trial probabilities from the southern and northern studies, we find a global post-trial probability of 2.59 × 10⁻⁷, suggesting that the observed correlation is unlikely to occur by chance. Theoretical modeling of one of these proposed neutrino-associated objects suggests that proton interactions with external radiation fields can generate a neutrino flux detectable by IceCube. These results further support the hypothesis that blazars are promising candidates for high-energy cosmic neutrino sources.