2D histogram of the stellar mass, M_* (top) and specific AGN luminosity, L_AGN/M*, defined in Thorne et al. (2022, bottom), as a function of frac_AGN for the QSO2 sample. The colour gradient indicates the density of sources for each bin. The median and standard deviation are represented by the solid and dashed orange lines, respectively. The vertical black line indicates the frac_AGN > 0.1 threshold used in Leja et al. (2018) to characterise sources with significant AGN contribution.