Diagnosing the AGN population origin of TeV neutrinos with their spatial correlation

Abstract

The recent detection of TeV neutrinos from some nearby Seyfert galaxy (e.g., NGC1068) by IceCube suggests that active galactic nuclei (AGNs) could make a significant contribution to diffuse astrophysical neutrinos. The absence of TeV gamma-rays from NGC1068 indicates neutrino production in a compact opaque region of gamma-rays. The vicinity of the supermassive black hole, such as the disk-corona, is an ideal region, where the high radiation density leads to efficient neutrino production and gamma-ray attenuation. Disk-corona models predict that the neutrino emission from AGNs correlates with X-ray emission, which traces the coronal activity. In this paper, we assess whether diffuse TeV neutrinos can originate from X-ray-emitting AGNs with Monte Carlo simulations, considering the predicted performance of future neutrino telescopes. We test this hypothesis by searching for spatial correlations between the X-ray AGN population and high-energy neutrinos, assuming that the neutrino flux scales with the AGN X-ray flux. Based on detailed Monte Carlo simulations, we find that an AGN origin of diffuse neutrinos can be tested at a significance of about $3\sigma$ with five years of IceCube-Gen2 observations. With improved angular resolution and sensitivity, a 30km$^{3}$-scale underwater neutrino telescope (such as the High-energy Underwater Neutrino Telescope) is expected to reach a significance of about $8\sigma$ with one year of exposure. The detection significance decreases if AGNs contribute partially to the total astrophysical neutrino flux. Our results highlight the critical role of angular resolution in diagnosing the AGN origin of diffuse TeV neutrinos.