The origin of the very-high-energy radiation of Centaurus A

As the closest known active galactic nucleus, Centaurus A provides a rich environment for astrophysical exploration, being detected from radio to gamma rays. Recently, very-high-energy gamma rays have been measured by the HESS observatory. The signal is associated with the jet, revealing the presence of relativistic electrons. However, the underlying acceleration mechanism remains uncertain. Several works have proposed that jet substructures, known as knots, may act as efficient particle accelerators. In this work, we model the particle acceleration in the knots, assuming they originate from the interactions between the jet and powerful stellar winds. The knots are modeled using relativistic hydrodynamics simulations using the PLUTO code. It is assumed that the shock injects relativistic electrons whose maximum energy depends on the radiation fields of the galaxy. The spectral index is found based on the radio and X-ray observed data, assuming a synchrotron origin. Inverse Compton scattering of the same electron population produces the very-high-energy $\gamma$ rays in this model. Our findings suggest that electrons accelerated at the knots are responsible for the $\gamma$-ray spectrum detected in the very-high-energy band. The possibility of knots as ultra-high-energy cosmic ray accelerators is also explored.