Example model fitting for the field galaxies’ concentration. A plot of SFR against M_⋆ for the field galaxies, colour coded by the average concentration within each SFR-M_⋆ bin. The bins containing at least 50 galaxies are shown. Panel a is the observed data, panel b is the model, and panel c is the residual from subtracting the model from the observations while the blue line indicates the split used for star-forming and quiescent galaxies (Eq. (2)) and the vertical dashed brown line indicates the mass limit. Panels a and b share a colour scale. Contours for the model are overlaid in panel b from low values (red) to high (blue).