Abstract
Context. Sulfur is a volatile chemical element that plays an important role in tracing the chemical evolution of the Milky Way and external galaxies. However, its nucleosynthesis origin and abundance variations in the Galaxy are still unclear because the number of available stellar sulfur abundance measurements is currently rather small. Aims. The goal of the present article is to accurately and precisely study the sulfur content of large number of stars located in the solar neighbourhood. Methods. We use the parametrisation of thousands of high-resolution stellar spectra provided by the AMBRE Project, and combine it with the automated abundance determination GAUGUIN to derive local thermodynamic equilibrium sulfur abundances for 1855 slow-rotating FGK-type stars. This is the largest and most precise catalogue of sulfur abundances published to date. It covers a metallicity domain as high as ∼2.5 dex starting at [M/H] ∼ −2.0 dex. Results. We find that the sulfur-to-iron abundances ratio is compatible with a plateau-like distribution in the metal-poor regime, and then starts to decrease continuously at [M/H] ∼ −1.0 dex. This decrease continues towards negative values for supersolar metallicity stars as recently reported for magnesium and as predicted by Galactic chemical evolution models. Moreover, sulfur-rich stars having metallicities in the range [ − 1.0, −0.5] have very different kinematical and orbital properties with respect to more metal-rich and sulfur-poor ones. Two disc components, associated with the thin and thick discs, are thus seen independently in kinematics and sulfur abundances. The sulfur radial gradients in the Galactic discs have also been estimated. Finally, the enrichment in sulfur with respect to iron is nicely correlated with stellar ages: older metal-poor stars have higher [S/M] ratios than younger metal-rich ones. Conclusions. This work has confirmed that sulfur is an α-element that could be considered to explore the Galactic populations properties. For the first time, a chemo-dynamical study from the sulfur abundance point of view, as a stand-alone chemical element, is performed.
Highlights
Sulfur is a chemical species of particular importance in the context of stellar nucleosynthesis and the chemical evolution of galaxies
We note that the atmospheric parameters associated with a given star have been averaged by adopting the same weighted mean (WM) procedure
We have presented LTE sulfur abundances derived from the three main components of the multiplet 8 system lines found around 675 nm, which are known to be poorly affected by NLTE effects
Summary
Sulfur is a chemical species of particular importance in the context of stellar nucleosynthesis and the chemical evolution of galaxies. This ratio is expected to decrease afterwards as soon as the amount of released iron increases with time Adopting such production sites, Galactic chemical evolution models quite successfully reproduce the main observed behaviour of sulfur and other α-elements as a function of the metallicity (among other recent studies, see Prantzos et al 2018; Grisoni et al 2017; Palla et al 2020), confirming that the major production site of S is Type II supernovae. At higher but still subsolar metallicities (−1.0 dex [Fe/H] 0.0 dex), and as expected for any αelement, the decline of [S/Fe] with metallicity in the Galactic disc is clearly observed and interpreted as the release of iron from Type Ia SNe at [Fe/H] −1 dex (see e.g., Chen et al 2002; Caffau et al 2005; Ryde 2006; Matrozis et al 2013) This supports the idea of a common nucleosynthetic origin for sulfur and other α -species.
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