Total [O III] luminosity versus hard X-ray luminosity (L_X(2–10 keV) for the SUPER (red circles) and KASHz targets (blue data points), the latter from a similar survey targeting X-ray selected AGN at high redshift. The combined data set of KASHz and SUPER show a positive correlation between the two quantities, shown by the black line. The shaded region represents the 1σ scatter on the relation. KASHz targets occupy the lower X-ray luminosity range compared to SUPER targets, which may explain the difference in the distribution of w₈₀ in the two surveys in Fig. 3.