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

TL;DR

This study provides evidence that Seyfert galaxies in the Southern Hemisphere are sources of high-energy neutrinos, using IceCube data and a collective signal search that indicates a 3-sigma excess over background expectations.

Contribution

The paper presents the first collective neutrino signal detection from Seyfert galaxies, supporting their role as sources of extragalactic high-energy neutrinos.

Findings

An excess of 6.7 neutrino events was observed from Seyfert galaxies.

The excess is statistically significant at the 3σ level.

Results support Seyfert galaxies as contributors to the high-energy neutrino flux.

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$\sigma$ level of significance. In this paper, we present new independent evidence that Seyfert galaxies contribute to the extragalactic flux of high-energy neutrinos.