Chemical (t_[Mg/Fe]) versus SFH (t₅₀) formation time scales. Circles are the ATLAS^3D sample with t_[Mg/Fe] calculated using the expression from Thomas et al. (2005), colour-coded according to M_JAM. In blue and orange we respectively show ZF-UDS-7329 with the Milky Way-like Kroupa and bottom-heavy IMFs. The vertical dashed line indicates the lower limit achieved in the ATLAS^3D sample for z ∼ 0 measurements.