Cumulative 0.5–2 keV (left) and 2–10 keV (right) fluxes per unit of square degree of the AGNs (dashed red line), nonactive galaxies (dash-dotted blue line) and galaxy clusters (dotted cyan line) simulated for the mocks used in this work. The overall distribution is plotted as a solid black line. The flux of the cosmic X-ray background measured by Cappelluti et al. (2017) is plotted in yellow, with 20% errors to account for the uncertainties in the CXB absolute flux level measured by different instruments.