BH mass fraction as a function of Δ_obs(< R_hl) (left panel) and Δ_obs(< 0.7R_hl) (right panel). Points show the simulation properties recomputed according to the magnitude and spatial selections adopted for the observations (see Sect. 4.1), whereas the vertical red lines show values obtained for the Galactic GCs studied in this work (along with errors as shaded areas). Simulations without BHs at 13 Gyr are shown at M_BH/M_GC = 5 × 10⁻⁶.