Top: relation between the X-ray luminosity L_X and the redshift z. Sources in green are the ones that are present in both the XMMFITCAT and MEXSAS catalogue, while the black dots are sources only present in the latter. The green circles are selected by Corral et al. (2015), when the number of counts is at least 50, and these sources are, on average, brighter than the ones not included. Bottom: ΔΓ−Δlog F_S correlation, plotted using the photon indices from our analysis, for the same two subsets. The green line shows the linear fit of just the green data, while the black line is the linear fit of the whole sample.