Beyond the two-infall model I. Indications for a recent gas infall with Gaia DR3 chemical abundances

Context. The recent Gaia Data Release 3 (DR3) represents an unparalleled revolution in Galactic archaeology, providing numerous radial velocities and chemical abundances for millions of stars as well as all-sky coverage.Aims We present a new chemical evolution model for the Galactic disc components (high- and low- alpha sequence stars) designed to reproduce the new abundance ratios provided by the General Stellar Parametriser-spectroscopy module for the Gaia DR3 and constrained by the detailed star formation (SF) histories for both the thick and thin disc stars inferred from previous Gaia releases.Methods. Sophisticated modelling based on previous Gaia releases have found evidence for narrow episodes of enhanced SF inferred in recent time. Additionally, Gaia DR3 indicated the presence of young (massive) low-alpha disc stars that show evidence of a recent chemical impoverishment in several elements. In order to reproduce these observables, we propose a new chemical evolution model in which the low-alpha sequence is generated by two distinct infall episodes. Hence, in this study we compare Gaia DR3 chemical abundances with the predictions of a three-infall chemical evolution model for the high- and low-alpha components.Results The proposed three-infall chemical evolution model nicely reproduces the main features of the abundance ratio [X/Fe] versus [M/H] (X=Mg, Si, Ca, Ti, alpha) of Gaia DR3 stars in different age bins for the considered alpha elements. Moreover, the most recent gas infall - which started similar to 2.7 Gyr ago - allowed us to predict accurately predict the Gaia DR3 young population which has experienced a recent chemical impoverishment.Conclusions. We extended previous chemical evolution models designed to reproduce APOGEE and APOKASC data in order to predict new Gaia DR3 chemical abundances. To this aim, we proposed a three-infall chemical evolution model to better trace both (i) the young population in Gaia DR3 with evidence of chemical impoverishment and (ii) the SF history from previous Gaia releases.

Automated summary

This study presents a new chemical evolution model for the Galactic disc components based on the recent Gaia Data Release 3. By comparing the predicted chemical abundances with the Gaia DR3 data, the proposed model successfully reproduces the abundance ratios of different alpha elements for stars in different age bins. It also accurately predicts the young population in Gaia DR3 that has experienced a recent chemical impoverishment.