Distribution of accretion parameter ℛ for barred (solid red line) and unbarred (dotted blue line) AGN. In the top panel, the black hole masses were derived with different M–σ relations that take into account the morphology as described in Sect. 2.2 with Eqs. (5) and (4). In the bottom panel, the black hole masses were derived with the M–σ relation obtained for a sample without distinction regarding morphology (Eq. (6)).