Plane of effective radius (R${}_{\mathrm{e}}^{\mathrm{maj}}$) versus stellar mass coloured by SSP-equivalent population parameters measured within one effective radius. Colours of the left, central, and right panels correspond to the mean stellar age, mean stellar metallicity, and the time taken to form 90% of the star in the galaxy, respectively. Dashed-black lines show constant velocity dispersion of 10, 20, 50, 100, 200, 300, 400, 500 km s⁻¹ from left to right, derived by the virial mass estimator M = 5R${}_{\mathrm{e}}^{\mathrm{maj}}$σ²/G. The LOESS smoothed version of this figure is shown in Figure 4.