BH mass fraction as a function of Δ. Colors depict the number of BHs in the simulation at 13 Gyr, while different symbols show the adopted fallback prescription in the initial conditions. Simulations without BHs at 13 Gyr are shown at M_BH/M_GC = 5 × 10⁻⁶. To account for fluctuations in the estimates arising due to the discrete nature of the simulations, we performed 500 different projections along the LOS, and for each of them, we measured Δ. The values shown are the median ones. Errors obtained computing the 16% and 84% percentiles of the distribution are also shown although barely visible.