High-energy neutrino astronomy — the neutrino connections to the cosmic-ray origin: present and future

Abstract

Abstract High-energy neutrino astronomy has been blooming. In addition to the possible identification of the blazar and Seyfert II galaxies as neutrino emitters, the present neutrino data has indicated some hints to characterize or constrain the origin of cosmic rays. Being motivated by the observational fact that the astrophysical neutrino background energy flux is comparable to that of ultrahigh-energy (UHE) cosmic rays, we derive the generic requirements that a major fraction of UHE cosmic ray sources must meet, if they are also responsible for the ∼ 100 TeV-energy cosmic neutrino background radiation. The source parameters characterizing the cosmic ray – neutrino unified scheme, such as the photon radiation luminosity and the cosmic ray luminosity density, suggest that the yet-unidentified cosmic ray and neutrino origins can be transient objects visible in the optical/NIR wavelength band. We propose a viable scheme of multimessenger observations to identify the sources using the neutrino multiplet detections.