Likelihood (shown as the colour map) for a given SFT, t_sf, and galaxy dynamical mass, M_dyn, as defined in Eq. (4) assuming an invariant canonical gwIMF and fitting only the [Mg/Fe] observations. The blue dotted curve indicates the downsizing relation of Thomas et al. (2005). The thin orange curve is the value of the highest likelihood for any given M_dyn that follows the yellow ridge-line, sharing the y-axis with the likelihood colour-bar.