Beyond the two-infall model

I. Indications for a recent gas infall with Gaia DR3 chemical abundances

¹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4, France
e-mail: emanuele.spitoni@oca.eu
² Osservatorio Astrofisico di Torino, Istituto Nazionale di Astrofisica (INAF), 10025 Pino Torinese, Italy
³ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, 40129 Bologna, Italy
⁴ Dipartimento di Fisica, Sezione di Astronomia, Universitádi Trieste, Via G.B. Tiepolo 11, 34131 Trieste, Italy
⁵ INAF Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34131 Trieste, Italy
⁶ INFN Sezione di Trieste, Via Valerio 2, 34134 Trieste, Italy

Received: 24 June 2022
Accepted: 13 December 2022

Abstract

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- α 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-α 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-α 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-α 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, α) of Gaia DR3 stars in different age bins for the considered α elements. Moreover, the most recent gas infall – which started ∼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.