FWHM of the broad component of Hβ versus R_FeII. The left panel displays the sample described in Sect. 8.2 (grey), and sources with a median spectral S/N ≥ 20 (blue). The right panel presents the same subsample of high S/N sources, colour coded to indicate the trend in Eddington ratio across the distribution. The grey dashed line marks the division between population A () and population B () sources. The size of the typical uncertainties, multiplied by a factor of five, in both variables for the high-S/N subsample is also shown.