Left: distribution of the mock populations on the (T_eff, log g) plane synthesized with constant continuum opacity. The spectra have resolution R = 12 000 and S/N = 100. Right: T_eff and log g of the spectra as derived by SP_Ace with constant continuum opacity. The blue points, red crosses, and green triangles represent the thin disk, halo/thick disk, and accreted stars, respectively. The solid, dashed, and dotted black lines show isochrones at [M/H] = 0.0 dex and 5 Gyr, [M/H] = −1.0 dex and 10 Gyr, and [M/H] = −2.0 dex and 10 Gyr, respectively. The light gray error bars represent the confidence intervals of the individual measurements.