Distribution in M_*,10 − Γ_*,10 space of galaxies following the average mass-size relation from HB09 (thick line). Lines parallel to it refer to galaxies offset from the average by a fixed amount in log R_e, as described on the labels. Lines perpendicular to the HB09 relation are obtained by varying the half-light radius at fixed total stellar mass (the numbers shown on each line are the corresponding values of log M_*).