Speaker
Description
Observation of high-energy neutrinos from the direction of the nearby active galaxy, NGC 1068, was a major step in identifying the origin of high-energy neutrinos. This observation revealed that high-energy neutrinos originated at the heart of active galaxies, that are opaque to very-high-energy gamma-ray emission.
his realization is reinforced by the excess of neutrinos in the direction of NGC 4151 and Circinus Galaxy, other nearby active galactic nuclei (AGNs). Understanding the vicinity of supermassive black holes with electromagnetic radiation is often challenging due to uncertainties associated with the absorption of emission in these dense environments, and neutrinos can be used as a powerful probe of the inner parts of the active galaxies. In this talk, we study the five brightest neutrino-active galaxies, NGC 1068, NGC 4151, CGCG 420-15, Circinus Galaxy, and NGC 7469. We employ the measured neutrino spectra together with the sub-GeV gamma-ray emission measured by the Fermi satellite to break the degeneracy and narrow down the parameter space of neutrino emission from the coronae of AGN. We further discuss the contributions of jet-quiet AGNs, whose properties are similar to NGC 1068, to the isotropic neutrino flux, through exploring possibilities that the neutrino luminosity function may deviate from the X-ray luminosity function. Our results confirm that jet-quiet AGNs can account for the all-sky neutrino flux in the 10–100 TeV range, in support of the original magnetically turbulent coronal emission of neutrinos.