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Active galactic nuclei (AGN) can launch and sustain powerful winds featuringmildly relativistic velocity and wide opening angle. Such winds, known asultra-fast outflows (UFOs), can develop a bubble structure characterized by aforward shock expanding in the host galaxy and a wind termination shockseparating the fast cool wind from the hot shocked wind. In this work weexplore whether diffusive shock acceleration can take place efficiently at thewind termination shock of UFOs. We calculate the spectrum of acceleratedparticles and find that protons can be energized up to the EeV range promotingUFOs to promising candidates for accelerating ultra-high energy cosmic rays(UHECRs). We also compute the associated gamma-ray and neutrino fluxes andcompare them with available data in the literature. We observe that high-energy(HE) neutrinos are efficiently produced up to hundreds of PeV while theassociated gamma rays could be efficiently absorbed beyond a few tens of GeV bythe optical-ultraviolet AGN photon field. By assuming a typical source densityof non-jetted AGN we expect that UFOs could play a dominant role as diffusesources of UHECRs and HE neutrinos. We finally apply our model to the recentlyobserved NGC1068 and we find out that under specific parametric conditions anobscured UFO could provide a sizeable contribution to the observed gamma-rayflux while only contributing up to ~10 per cent to the associated neutrinoflux.

Diffusive shock acceleration at EeV and associated multimessenger flux from ultra-fast outflows driven by Active Galactic Nuclei