Mass of the remnant BH against the mass of the host galaxy for mergers occurring in the range z = 3.5 − 4. Blue crosses correspond to the overall population of numerical remnant BHs, crimson triangles to AGN-dominated mergers and green circles to observable mergers in the X-ray. Lines denote the geometric average of M_• in bins of M_*, while shaded regions denote the 1σ error in the average. We note that all observable mergers are AGN-dominated sources. AGN-dominated mergers are more massive, at fixed M_* compared to all merger remnants: this is an effect of requiring the AGN to be bright, and brighter than the galaxy. This effect is stronger for observable mergers. A similar trend is found at all redshifts.