Exploring TeV-emitting radio galaxies with CTAO: insights into the physics of relativistic jets

About 10% of active galactic nuclei host relativistic jets. When misaligned with our line of sight, these systems are observed as radio galaxies, spanning a wide range of accretion regimes and morphologies. Radiatively efficient sources (HERGs) host thin disks and powerful jets, while radiatively inefficient systems (LERGs and LLRGs) are associated with ADAF-like flows and lower luminosities. Accretion modes and jet power are thought to be tightly linked, although recent findings challenge this simple paradigm. This Ph.D. Thesis investigates accretion–ejection processes in radiatively inefficient radio galaxies through a multiwavelength observational and modeling approach, focusing on two TeV-detected sources with very different properties: the FR I galaxy 3C 264 and the compact LLRG NGC 4278. For 3C 264, I reconstructed the flaring and post-flaring spectral energy distributions (SEDs) using contemporaneous X-ray, GeV, and TeV data. For the first time for this source, I applied a time-dependent leptonic model to describe the transition between high and low states, revealing a hard transient component during the flare with a jet luminosity of ~10^44 erg/s dominating the X-ray and very-high-energy emission. For NGC 4278, detected up to ~15 TeV by LHAASO, I achieved the first robust GeV detection (~4.3σ) through a refined Fermi-LAT analysis, firmly associating the source with the TeV counterpart. SED modeling indicates a low-power jet (~10^42 erg/s) dominated by kinetic energy, with episodic particle injection and likely jet confinement within the host galaxy. Hadronic modeling shows the expected neutrino flux to be about one order of magnitude below current IceCube sensitivity. Despite their different morphologies and energetics, both sources display flares with similar timescales and spectral properties, suggesting a common acceleration mechanism. I also show that CTAO will significantly enhance the detection and characterization of both steady and transient emission in such systems.