Incidence of RDAGN as a function of stellar mass, shown for different galaxy populations. From top to bottom, the galaxies are divided by stellar velocity dispersion (an indicator of the black hole mass), the number of neighbors within 200 kpc (an indicator of the cosmic environment), and Hubble type (galaxy morphology). RDAGN tend to be located in host galaxies with larger stellar velocity dispersions, denser environments, and early-type morphologies. We find that most galaxies with the largest stellar dispersion (σ_* > 264 km s⁻¹) host RDAGN, which suggests that the most massive SMBHs are always accreting in the radio mode.