Orthogonal sections of the log(FWHM_Hβ,br)−log(L_Hβ,br)−R_Fe parameter space. Specifically we have (left) R_Fe versus log(L_Hβ, br) in (colour-coded) bins of FWHM_Hβ,br, and (right) R_Fe versus FWHM_Hβ,br in (colour-coded) bins of log(L_Hβ, br). The thick-edged diamond and star represent the values derived from the composite spectra. The colour-coded lines represent the third quantity evaluated on the binned sources of the control samples. SBS_0335-052E (black thick edge pentagon) has been shifted for a tighter image layout. It is clear that, while the high-luminosity objects of the sample reside – albeit with some scatter – in the expected locus of the parameter space according to the control sample, the low-luminosity objects exhibit far lower R_Fe. Interestingly, two low-luminosity objects (JADES-029777 and XID2028) detach from the bulk of the faint sample, being close to the R_Fe expected. As we discuss further in Sect. 5.5, these are the two only faint AGNs that are X-ray detected.