Search for High-energy Neutrinos from AGN Cores

Abstract

IceCube is a cubic-kilometer Cherenkov telescope operating at the South Pole. In 2013 IceCube discovered high-energy astrophysical neutrinos and has more recently found compelling evidence for a flaring blazar being a source of high-energy neutrinos. However, as blazars can only be responsible for a small fraction of the observed neutrino flux, the sources responsible for the majority of the detected neutrinos remain unknown. In this work, we explore the possibility that the observed neutrino flux is produced in the cores of Active Galactic Nuclei (AGN). Various models have predicted neutrino emission from the accretion disks of AGN. According to these models, the neutrino luminosity would not depend strongly on either the orientation or other parameters of the relativistic jet. Both jetted and non-jetted AGN could contribute to the neutrino flux. We perform a stacking analysis to test for correlation between various sub-populations of AGN and high-energy neutrinos using a decade of IceCube data. We select AGN based on their radio emission, infrared color properties, and X-ray flux using the NVSS, AllWISE, ROSAT and XMMSL2 catalogs. We use the accretion disk luminosity, estimated from the observed soft X-ray flux, to weight the contribution of selected galaxies to the neutrino signal.