Speaker
Description
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 the gamma-ray blazars detected in the GeV energy band can only be responsible for a small fraction of the observed cosmic neutrino flux below 100 TeV, the sources responsible for the emission of the majority of the detected neutrinos are still unknown. In this contribution, we explore the possibility that the observed neutrino flux is produced in the cores of Active Galactic Nuclei (AGN), induced by accelerated cosmic rays in the accretion disk region. We present a likelihood analysis based on eight years of IceCube data, searching for a cumulative neutrino signal from three AGN samples created for this work. The neutrino emission is assumed to be proportional to the accretion disk luminosity estimated from the soft X-ray flux. We select AGN based on their radio emission, infrared color properties, and X-ray flux using the NVSS, AllWISE, ROSAT and XMM-SL2 catalogs. For the largest sample in this search, an excess of high-energy neutrino events with respect to an isotropic background of atmospheric and astrophysical neutrinos is found, corresponding to a post-trial significance of 2.60σ. If interpreted as a genuine signal with the assumptions of a proportionality of X-ray and neutrino fluxes, this observation implies that at 100 TeV, 27%-100% of the observed neutrinos arise from particle acceleration in the core of AGN.
