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Powerful radio-loud active galactic nuclei (AGN) with large Mpc-scale jetshave been theoretically motivated as emitters of high-energy cosmic rays.Recent radio observations have established a populous class of young radio-loudgalaxies with compact ($< 1$ kpc) symmetric jets that are morphologicallysimilar to large-scale AGNs. We show that these compact AGNs, so-called compactsymmetric objects (CSOs), can accelerate protons up to $10^{20}$ eV at theirhot spots via a Fermi type mechanism on the assumption of efficientacceleration. The required magnetic field strengths are comparable to thosederived from the minimum energy condition. We further show that the acceleratedprotons can escape through the photon fields of the cocoon without significantenergy loss. However, the local number density of powerful CSOs is insufficientfor CSOs to power the entire observed flux of ultra-high-energy cosmic rays,providing maximally only a few percent. A heavy composition of UHECRs allowsmore CSOs to accelerate particles to UHECR energies, but escaping the cocoon isdifficult. We comment on a method that may test CSOs as UHECR sources.

The Production of Ultra High Energy Cosmic Rays during the Early Epochs of Radio-loud AGN