Recoil velocity of the merged BH due to a merger between two BHs as a function of their mass ratio q​ = ​m₂/m₁. The cases shown are (i) non-spinning BHs (red), (ii) a strongly spinning BH a₁​ = ​0.9 where the spin is aligned with the orbit (blue), (iii) strongly spinning BHs a₁​ = ​a₂​ = ​0.9 (with respect to the maximum possible a₁​ = ​1) with the spins aligned with the orbit (magenta), and (iv) a strongly spinning BH a₁​ = ​0.9 with the spin inclined at 10° or at 30° with respect to orbit, spanning the full range of phases for the encounter (diagonal lines area and shaded area, respectively). Marked in comparison are the fiducial and maximum escape velocities from an FFB galactic disc of 171 and 700 km s⁻¹ (black dashed, gray dashed).