Chemodynamical properties and ages of metal-poor stars in S-PLUS

Abstract

ABSTRACT Metal-poor stars are key to our understanding of the early stages of chemical evolution in the Universe. New multifilter surveys, such as the Southern Photometric Local Universe Survey (S-PLUS), are greatly advancing our ability to select low-metallicity stars. In this work, we analyse the chemodynamical properties and ages of 522 metal-poor candidates selected from the S-PLUS data release 3. About 92 per cent of these stars were confirmed to be metal-poor ([Fe/H] ≤ −1) based on previous medium-resolution spectroscopy. We calculated the dynamical properties of a subsample containing 241 stars, using the astrometry from Gaia Data Release 3. Stellar ages are estimated by a Bayesian isochronal method formalized in this work. We analyse the metallicity distribution of these metal-poor candidates separated into different subgroups of total velocity, dynamical properties, and ages. Our results are used to propose further restrictions to optimize the selection of metal-poor candidates in S-PLUS. The proposed astrometric selection (parallax >0.85 mas) is the one that returns the highest fraction of extremely metal-poor stars (16.3 per cent have [Fe/H] ≤ −3); the combined selection provides the highest fraction of very metal-poor stars (91.0 per cent have [Fe/H] ≤ −2), whereas the dynamical selection (eccentricity >0.35 and discness < 0.75) is better for targeting metal-poor (99.5 per cent have [Fe/H] ≤ −1). Using only S-PLUS photometric selections, it is possible to achieve selection fractions of 15.6, 88.5, and 98.3 per cent for metallicities below −3, −2, and −1, respectively. We also show that it is possible to use S-PLUS to target metal-poor stars in halo substructures such as Gaia-Sausage/Enceladus, Sequoia, Thamnos, and the Helmi stream.