The I_e − R_e plane at different redshift for Illutris-1. From top left to bottom right, we can see the distribution of galaxies at z = 4, z = 3, z = 2.2, z = 1.6, z = 1.0, z = 0.6, z = 0.2, and z = 0. The colored dots mark the galaxies with β > 0 at each epoch, whereas the black symbols mark those with β ≤ 0. The crosses mark the galaxies with SFR greater than the mean ⟨SFR⟩ at each epoch, while the open squares show those with SFR lower than ⟨SFR⟩. The arrows indicate the average direction of motion predicted on the basis of the values of β from Eq. (3); see also Table 1. The colored arrows mark the average for the galaxies with β > 0 and the black arrows those with β ≤ 0. Their length is not related or proportional to any other quantity; it was chosen for graphical reasons.