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Fig. 7.

image

Chemical evolution model results for the time evolution of [M/H] (upper panel) and [α/Fe] (lower panel) distributions produced from the age and metallicity uncertainties reported by VSA18 following Eqs. (10) and (11). With the purple filled pentagons we label the stellar populations formed during the first infall (“high-α” sequence) at Galactic time t <  tmax = 4.3 Gyr (time for the maximum infall on the second gas infall) before including the errors. Analogously, the filled pentagons green circles represent the stellar populations formed in “low-α” sequence at Galactic time t >  tmax = 4.3 Gyr. The pentagon size indicates the local number density of formed stars normalised to maximum value. We also show the contour density curves of the observed “high-α” stars (black and blue lines stand for the higher and lower levels, respectively) and “low-α” stars (black and white lines stand for the higher and lower levels, respectively) of the VSA18 sample.

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