The Interplay between accelerated Protons, X-rays and Neutrinos in the Corona of NGC 1068: Constraints from Kinetic Plasma Simulations

Abstract

We examine properties of accelerated protons potentially responsible for the neutrino excess observed in the direction of NGC 1068, using constraints from kinetic Particle-in-Cell (PIC) simulations. We find that i) coronal X-rays and Optical/Ultra-Violet light in the inner disk lead to efficient absorption of hadronic $\gamma$-rays within 100 Schwarzschild radii from the black hole; ii) protons accelerated from the coronal thermal pool cannot account for the observed neutrinos; and iii) explaining the observed signal requires an injection of protons with a hard spectrum, peaking at $\gamma_p\sim 10^3-10^4$, into the turbulent magnetically-dominated corona, where they are confined and re-accelerated. The resulting neutrino signal can be consistent with IceCube observations. In our most favorable scenario, the injected protons are pre-accelerated in intermittent current sheets in the vicinity of the black hole, occurring either at the boundary between the disk and the outflow or during magnetic flux eruption events.