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

Abstract: The recent IceCube detection of TeV neutrinos from some nearby Seyfert galaxy (e.g., NGC~1068) suggests that active galactic nuclei (AGN) could make a significant contribution to the diffuse flux of astrophysical neutrinos. The absence of TeV gamma-rays from NGC~1068 indicates neutrino production in compact gamma-ray-opaque region. The vicinity of the supermassive black hole, such as disk-corona, is an ideal region, where the high radiation density leads to efficient neutrino production as well as the 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 the X-ray AGN population origin for TeV neutrinos can be tested by using the spatial correlation between the neutrino population and X-ray AGN population with future neutrino telescopes. By performing simulations, we find that, the AGN origin of the neutrino background above 100\,TeV can be tested at a confidence level of $\sim2.4σ$ with five-year observations of IceCube-Gen2, which has an angular resolution of $\sim0.2$ degree. With better angular resolution and sensitivity in the energy range of above $300$\,TeV, a 30-${\rm km^3}$ underwater neutrino telescope, such as High-energy Underwater Neutrino Telescope (HUNT), is expected to reach a significance of $\sim8.6σ$ in testing the association after five years of exposure.