log[R_s] vs. log[M_s] relation for compact galaxies (filled blue circles) and their best fit (blue dashed line). The red open circles are the ETGs from Bernardi et al. (2010) plotted here for comparison, and the red dashed line is their best-fit. The large filled circles are the 12 ancillary models (black the efficiency of star formation ϵ_sff = 1, green for ϵ_sff = 0.5, and red for ϵ_sff = 0.1). The thin straight lines are the present-day MRRs of model galaxies that started their collapse at different redshifts, namely z_f = 1, z_f = 5, z_f = 8, and z_f = 10 from top to bottom. The lines are given by Eq. (34).