The SMBH mass–luminosity plane of z > 5.8 quasars, the BH mass M_BH of which have been measured to date with Mg II. The symbols and colors are the same as in Figure 6. The quoted virial masses are derived using the scaling relation of Vestergaard & Osmer (2009). For non-HSC quasars, we quote their Mg II line and continuum measurements to calculate M_BH and bolometric luminosity with the same relation and cosmology as those applied for the HSC quasars (Equation (4)). The systematic uncertainty of the virial BH mass measurement (0.5 dex; Shen 2013) is included in the error bars. Contours show the distribution of the z ∼ 2 SDSS DR7 quasars (Shen et al. 2011). The diagonal lines show Eddington luminosities of L_bol/L_Edd = 1, 0.1, and 0.01 from top left to bottom right.