Left: magnesium [Mg/Fe] versus iron [Fe/H] abundances from ASPCAP for the calibration sample of Kepler/APOGEE main-sequence stars. The high-α/low-α linear cutoff is shown with the blue dotted line. The green heatmap represents the low-α (thin-disk) calibration sample, and the red heatmap represents the high-α (thick-disk) calibration sample. Center: the thin-disk calibration sample in V_ϕ versus ﹩\sqrt{{V}_{r}^{2}+{V}_{z}^{2}}﹩ velocity space. The mean of the low-α component of the GMM is designated with a cross, and the concentric circles represent the 1σ and 2σ regions. Right: same as the center, but for the high-α calibration sample.