Abundance ratios of [Si/Fe] as a function of [M/H] predicted by our three-infall synthetic chemical evolution model for different age bins taking into account observational errors (see Eqs. (6)–(8)) are indicated by colour-coded hexagons. The colour-coding stands for the normalised predicted total number of formed stars in the [Si/Fe] versus [M/H] area covered by each hexagon. Gaia DR3 stars are indicated by empty hexagons: the grey hexagons enclose between two and six stars, and the light-blue hexagons enclose between six and 20. Finally, the blue hexagons contain more than 20 stars. In the third panel of the second row, we show model predictions for all the ages and, we also indicate results without the errors in blue the model. In each panel we also report the median vertical dispersion velocity values computed at different age bins.