Consequences of relativistic proton injection in active galactic nuclei

Nonthermal processes in active galactic nuclei (AGNs) can lead to the efficient production of extremely relativistic protons, with energies of up to 10⁷^-10⁸^ GeV. Such protons would interact with the intense radiation field as well as the ambient plasma through a variety of processes, including inelastic proton-proton collisions, photomeson production, and pgaMMA pair production. We analyze the outcomes of these processes, to determine: (1) how they affect the distribution of proton energies; and (2) what kinds of secondary particles they produce. We show that ~10%-30% of the injected proton energy can go into neutrons and neutrinos which escape the nucleus. We derive analytic expressions for the energy distributions of emergent neutrons and neutrinos, as well as primary gamma rays (most of which are absorbed in situ), and present quantitative results for illustrative cases. Dynamic consequences of the neutron and neutrino outputs are briefly described. Because of their high energies, the neutrons can travel as far as 1-100 pc before decaying, suffering no adiabatic losses en route. Ultrarelativistic protons deposited through neutron decay, coupled to tHe local magnetic field, can drive a powerful wind and contribute to the confinement of emission-line clouds. TeV neutrinos irradiating late-type main-sequence stars are absorbed and may lead to stellar "bloating" and enhanced mass loss. These processes are potentially of great importance to theories of AGNs and will form the foci of subsequent papers. A test for the production of ultrarelativistic protons would be the detection of >~ TeV neutrinos, which could be accomplished by a DUMAND-type detector.