High-energy electromagnetic, neutrino, and cosmic-ray emission by stellar-mass black holes in disks of active galactic nuclei

Some Seyfert galaxies are detected in high-energy gamma rays, but the mechanism and site of gamma-ray emission are unknown. Also, the origins of the cosmic high-energy neutrino and MeV gamma-ray backgrounds have been veiled in mystery since their discoveries. We propose emission from stellar-mass BHs (sBHs) embedded in disks of active galactic nuclei as their possible sources. These sBHs are predicted to launch jets due to the Blandford–Znajek mechanism, which can produce intense electromagnetic, neutrino, and cosmic-ray emissions. We investigate whether these emissions can be the sources of cosmic high-energy particles. We find that emission from internal shocks in the jets can explain gamma rays from nearby radio-quiet Seyfert galaxies including NGC 1068, if the Lorentz factor of the jets (Γj) is high. On the other hand, for moderate Γj, the emission can significantly contribute to the background gamma-ray and neutrino intensities in the ~MeV and ≲PeV bands, respectively. Furthermore, for moderate Γj with efficient amplification of the magnetic field and cosmic-ray acceleration, the neutrino emission from NGC 1068 and the ultrahigh-energy cosmic rays can be explained. These results suggest that the neutrino flux from NGC 1068 as well as the background intensities of MeV gamma rays, neutrinos, and the ultrahigh-energy cosmic rays can be explained by a unified model. Future MeV gamma-ray satellites will test our scenario for neutrino emission.