Chemical abundance structure of the MW disc in the [Mg/Fe] − [Fe/H] plane. Left panel shows the number of stars with abundances available in our APOGEE selection, while the right panel depicts the stellar mass-weighted distribution obtained using the orbit superposition method. In both panels, the maps are normalised by the maximum value. The yellow lines show the distributions of [Mg/Fe] and [Fe/H] separately, where the contribution from high- and low-α populations is marked by blue and red, respectively. The solid white line is used to separate high- and low-α populations.