2013A&A...558A..19W

Observations of the FRI radio galaxy CentaurusA in radio, X-ray, and gamma-ray bands provide evidence for lepton acceleration up to several TeV and clues about hadron acceleration to tens of EeV. Synthesising the available observational constraints on the physical conditions and particle content in the jets, inner lobes and giant lobes of CentaurusA, we aim to evaluate its feasibility as an ultra-high-energy cosmic-ray source. We apply several methods of determining jet power and affirm the consistency of various power estimates of ∼1x10⁴³erg/s. Employing scaling relations based on previous results for 3C31, we estimate particle number densities in the jets, encompassing available radio through X-ray observations. Our model is compatible with the jets ingesting ∼3x10²¹g/s of matter via external entrainment from hot gas and ∼7x10²²g/s via internal entrainment from jet-contained stars. This leads to an imbalance between the internal lobe pressure available from radiating particles and magnetic field, and our derived external pressure. Based on knowledge of the external environments of other FRI sources, we estimate the thermal pressure in the giant lobes as 1.5x10^–12dyn/cm2, from which we deduce a lower limit to the temperature of ∼1.6x10⁸K. Using dynamical and buoyancy arguments, we infer ∼440-645Myr and ∼560Myr as the sound-crossing and buoyancy ages of the giant lobes respectively, inconsistent with their spectral ages. We re-investigate the feasibility of particle acceleration via stochastic processes in the lobes, placing new constraints on the energetics and on turbulent input to the lobes. The same ``very hot'' temperatures that allow self-consistency between the entrainment calculations and the missing pressure also allow stochastic UHECR acceleration models to work.