Centaurus A: Opportunities to unveil particle acceleration with the CTAO

Abstract

As the nearest radio galaxy, Centaurus A (Cen A) has been observed across multiple wavelengths and over a broad range of angular scales, providing valuable insights into the functioning of radio galaxies. However, despite being a known source of gamma rays, the physical mechanisms responsible for these high energy emissions remain unclear. In this study, we explore the capabilities of the Cherenkov Telescope Array Observatory (CTAO) to provide insights into the origin of the gamma-ray emission from Cen A. Using simulated observations based on the CTAO Instrument Response Functions (IRF) for the Alpha Configuration of telescopes, we investigate both the spectral and morphological domains to assess the observatory's potential to constrain competing models of particle acceleration in the kiloparsec-scale jet and the Southern Giant Lobe. For the jet, we explore CTAO observations with t=50 and 200h for different leptonic and hadronic origin scenarios for the very-high-energy gamma-ray emission. We show that longer observation campaigns (t=200h) would probe the presence of hard spectral components extending to tens of TeV. Morphological simulations demonstrate that CTAO can resolve the extended gamma-ray emission along the jet, discriminating between point-like and Gaussian spatial models within t=50h, assuming a known background model and an optimistic zenith angle $\vartheta=$20°. Under similar hypotheses, we studied the Giant Lobes evaluating both diffuse and filamentary emission templates for the S1 region detected by Fermi-LAT. We found that CTAO-South can be sensitive to hadronic scenarios with proton energies extending beyond 10 TeV, for the Alpha Configuration and $\vartheta=$20°. Overall, our results indicate that CTAO observations of Cen A can provide a decisive step toward unveiling the mechanisms driving the high-energy emission and particle acceleration in radio galaxies