Single-epoch M_BH comparison. The estimates based on C IVλ1549 (magenta pentagons) and Mg IIλ2798 (cyan crosses) are shown against the broad Hβλ4861 values. The typical systematic uncertainty of the calibrations is shown in the top left corner with the same colour-coding, while the dashed black line represents the 1:1 relation. The dotted lines join BH mass estimates for the same object according to different emission lines. The Hβ BH mass for J1111+2437 is denoted as an upper limit since the line profile is not well defined (see Appendix E for details).