Abundance–age relations with red clump stars in open clusters

Abstract

Context. Precise chemical abundances coupled with reliable ages are key ingredients to understanding the chemical history of our Galaxy. Open clusters (OCs) are useful for this purpose because they provide ages with good precision. Aims. The aim of this work is to investigate the relation between different chemical abundance ratios and age traced by red clump (RC) stars in OCs. Methods. We analyzed a large sample of 209 reliable members in 47 OCs with available high-resolution spectroscopy. We applied a differential line-by-line analysis, performing a comprehensive chemical study of 25 chemical species. This sample is among the largest samples of OCs homogeneously characterized in terms of atmospheric parameters, detailed chemistry, and age. Results. In our metallicity range (−0.2 < [M/H] < +0.2) we find that while most Fe-peak and α elements show a flat dependence on age, the s-process elements show a decreasing trend with increasing age with a remarkable knee at 1 Gyr. For Ba, Ce, Y, Mo, and Zr, we find a plateau at young ages (< 1 Gyr). We investigate the relations between all possible combinations among the computed chemical species and age. We find 19 combinations with significant slopes, including [Y/Mg] and [Y/Al]. The ratio [Ba/α] shows the most significant correlation. Conclusions. We find that the [Y/Mg] relation found in the literature using solar twins is compatible with the one found here in the solar neighborhood. The age–abundance relations in clusters at large distances(d > 1 kpc) show larger scatter than those in clusters in the solar neighborhood, particularly in the outer disk. We conclude that, in addition to pure nucleosynthetic arguments, the complexity of the chemical space introduced by the Galactic dynamics must be taken into account in order to understand these relations, especially outside of the local bubble.

The consistency of chemical clocks among coeval stars

“…These relations can be explained with similar arguments as [Y/Mg], which is widely discussed in the literature (e.g. Nissen 2015;Delgado Mena et al 2019;Casamiquela et al 2021). The argument is the very different timescales for the production of an alpha-capture element such as Mg in comparison with a neutron-capture element such as Y.…”

“…When combined, a tight relation of [Y/Mg] can be found for stars of the same metallicity but different ages. Jofré et al (2020) and Casamiquela et al (2021) found that the clocks showing largest age dependency involved neutron-Figure 5. Differential abundance as a function of elemental condensation temperature from the H20 systems and our sample of wide binaries that present a slope greater than 3 × 10 −5 dex/K.…”

“…whether it belongs to the thin disk or to the thick disk), because at different locations stars can have different metallicities. Most recently, Casamiquela et al (2021) in more detail, they find that the clusters located outside the solar neighborhood appear to have a significantly greater dispersion in abundances compared to the local ones, without finding any dependence on metallicity because of the narrow range in [Fe/H] of their sample. They attribute this finding to galactic dynamics processes, such as radial migration of stars or clusters, which are more likely to be sampled when covering a wider range in distance and can trace different chemical evolutionary histories.…”

“…In particular, Feltzing et al (2017) Casali et al (2020) and [Sr/Mg] by Nissen et al (2020) showing a significant effect. Casamiquela et al (2021) used a large sample of open clusters with well-known ages, to show that offsets and dispersion are introduced in the age-abundance relations when reaching out of the local bubble (d > 1 kpc). Therefore, it is not straightforward to apply these relations outside the solar-metallicity solar-vicinity.…”

The Gaia-ESO survey: Age-chemical-clock relations spatially resolved in the Galactic disc

“…Spina et al 2016;Delgado Mena et al 2019;Jofré et al 2020), the next steps were the following: i) to clarify the applicability of these relationships with luminosity class (dwarf or giant) (see, e.g. Tucci Maia et al 2016b;Slumstrup et al 2017;Casamiquela et al 2021), metallicity (see, e.g Feltzing et al 2017Delgado Mena et al 2019;Casali et al 2020), and population type (thin disc, thick disc, halo) (see, e.g. Titarenko et al 2019;Nissen et al 2020;Tautvaišienė et al 2021), or even in dwarf galaxies (Skúladóttir et al 2019); ii) to calibrate them with a sample of stars with reliable age determination, which are usually open star clusters (OCs), solar twins, or targets with asteroseismic observations.…”