X-ray luminosity as a function of redshift. The different dashed lines display luminosities of sources with Γ_X = 2.0 for increasing z and a fixed X-ray flux: from top (dashed line) to bottom (dash-double dot line), we display F_{X,  0.2 − 2.3 keV} from 10⁻¹¹ erg cm⁻² s⁻¹ down to 10⁻¹⁴ erg cm⁻² s⁻¹ in steps of 10. We show the main band eROSITA luminosity in panel a, following the color scheme introduced in Fig. 3; and the 2–10 keV X-ray luminosity in panel b. In gray the BlazEr1 sample is shown. Orange points are based on NuSTAR data (Middei et al. 2022), blue points on Swift-BAT (Marcotulli et al. 2022), using the redshifts from BZCAT and 3HSP for the NuSTAR and the redshifts from Marcotulli et al. (2022) and adopting their best fit models.