Ratio between the outflow (molecular or UFO) momentum flux and the radiative momentum flux as a function of the outflow velocity. Star = PDS 456; blue symbols are AGNs with L_Bol <  10⁴⁶ erg s⁻¹ (Feruglio et al. 2015; Longinotti et al. 2018); red symbols are AGNs with L_Bol  ∼ 10⁴⁶ − 10⁴⁸ (Tombesi et al. 2015; Veilleux et al. 2017; Feruglio et al. 2017, and this work). Filled symbols represent molecular outflows and open symbols show UFOs. The dashed line is the expectation for a momentum-driven outflow. The dot-dashed line represents the prediction for an energy-driven outflow with Ṗ_mol/Ṗ_rad = v_UFO/v. The solid lines show the expected Ṗ_mol/Ṗ_rad for a given luminosity and for different μ(L) = Ṁ_ion/Ṁ_mol. The red(blue) shaded area shows the uncertainty on Ṗ_mol/Ṗ_rad at L_Bol ∼ 10⁴⁷(10⁴⁵) erg s⁻¹, given the rms scatter on Ṁ_ion according to Eq. (2).