Evidence for neutrino emission from X-ray Bright Seyfert Galaxies in the Southern Hemisphere using Enhanced Starting Track Events with IceCube

TL;DR

The study investigates whether X-ray bright Seyfert galaxies contribute to the high-energy extragalactic neutrino flux by analyzing IceCube data (2011–2021) for muon neutrinos with vertices inside the detector, focusing on Southern sources guided by disk-corona neutrino production predictions. It performs both individual-source and stacking analyses of 14 southern Seyferts selected from the Swift-BAT survey, using X-ray fluxes to predict expected neutrino yields under the disk-corona model. The stacking search reports an excess of $6.7_{-3.2}^{+4.0}$ events with a significance of $3\sigma$ relative to background, providing independent evidence that Seyfert galaxies contribute to the extragalactic high-energy neutrino flux. These results support the disk-corona scenario for neutrino production in AGN cores and demonstrate a viable approach for identifying Southern-sky neutrino sources.

Abstract

IceCube recently reported the observation of TeV neutrinos from the nearby Seyfert galaxy NGC~1068, and the corresponding neutrino flux is significantly higher than the upper limit implied by observations of GeV-TeV gamma rays. This suggests that neutrinos are produced near the supermassive black hole, where the radiation density is high enough to obscure gamma rays. We use a set of muon neutrinos with interaction vertices inside the detector, which have good sensitivity to sources in the Southern sky, from IceCube data recorded between 2011 and 2021. We then search for individual and collective neutrino signals from 14 Seyfert galaxies in the Southern Sky selected from the Swift Burst Alert Telescope (BAT) AGN Spectroscopic Survey. Using the correlations between keV X-rays and TeV neutrinos predicted by disk-corona models, and assuming production characteristics similar to NGC~1068, a collective neutrino signal search reveals an excess of $6.7_{-3.2}^{+4.0}$ events, which is inconsistent with background expectations at the 3$σ$ level of significance. In this paper, we present new independent evidence that Seyfert galaxies contribute to the extragalactic flux of high-energy neutrinos.