Comparison with Galactic disc present-day observables. In each panel, model predictions are drawn with solid lines and the red and blue colours indicate the high-α (low-α) phases, respectively. Left panel: evolution of the surface mass density of stars (σ_*, solid line) and gas (σ_gas, dashed line) predicted by the two-infall chemical evolution model presented in this study with model parameters reported in Table 1. The purple star indicates the observed present-day σ_* value given by McKee et al. (2015). The magenta star represents the present-day σ_gas value averaging between the Dame (1993) and Nakanishi & Sofue (2003, 2006) datasets presented by Palla et al. (2020) (here shown only at 8 kpc). The 1σ errors are reported in grey. Middle panel: predicted time evolution of the SFR. The shaded grey area indicates the measured range in the solar annulus suggested by Prantzos et al. (2018). Right panel: Evolution of the type Ia SN rate (dashed line) and CC-SN rate (solid line) predicted by the model for the whole Galactic disc. The orange star represents the observed type Ia SN rate reported by Cappellaro & Turatto (1997), while the green one represents the observed CC-SN rates from Li et al. (2011). The 1σ and 2σ errors are reported with grey and black bars, respectively.