Differential abundances of open clusters and their tidal tails: Chemical tagging and chemical homogeneity

Casamiquela, L.; Tarricq, Y.; Soubiran, C.; Blanco-Cuaresma, S.; Jofré, P.; Heiter, U.; Maia, M. Tucci

doi:10.1051/0004-6361/201936978

Cited by 50 publications

(59 citation statements)

References 67 publications

(81 reference statements)

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“…Open clusters (OCs) provide an interesting alternative to solar twins for testing chemical clocks because their age and distance determinations are much more accurate and precise than for field stars at the same distances. Also, the fact that OCs are chemically homogeneous, at least up to ∼0.02 dex (Liu et al 2016;Casamiquela et al 2020), allows for a much more precise chemical abundance determination when several members are observed per cluster, as we see in the present study. This is why they have been used extensively to trace the Galactic thin disk abundance patterns (e.g., Magrini et al 2017;Donor et al 2018;Casamiquela et al 2019).…”

Section: Introductionsupporting

confidence: 67%

Abundance–age relations with red clump stars in open clusters

Casamiquela

Soubiran

Jofré

et al. 2021

A&A

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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.

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Section: Introductionsupporting

confidence: 67%

Abundance–age relations with red clump stars in open clusters

Casamiquela

Soubiran

Jofré

et al. 2021

A&A

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“…Open clusters are most commonly used to demonstrate chemical homogeneity and most show a high level of homogeneity (De Silva et al 2006;Bovy 2016;Casamiquela et al 2020). However, open clusters represent only a small fraction of the clusters that have survived past 100 Myr.…”

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confidence: 99%

The GALAH survey: Chemical homogeneity of the Orion complex

Kos

Bland-Hawthorn

Buder

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Due to its proximity, the Orion star forming region is often used as a proxy to study processes related to star formation and to observe young stars in the environment they were born in. With the release of Gaia DR2, the distance measurements to the Orion complex are now good enough that the three dimensional structure of the complex can be explored. Here we test the hypothesis that, due to non-trivial structure and dynamics, and age spread in the Orion complex, the chemical enrichment of youngest stars by early core-collapse supernovae can be observed. We obtained spectra of 794 stars of the Orion complex with the HERMES spectrograph at the Anglo Australian telescope as a part of the GALAH and GALAH-related surveys. We use the spectra of ∼300 stars to derive precise atmospheric parameters and chemical abundances of 25 elements for 15 stellar clusters in the Orion complex. We demonstrate that the Orion complex is chemically homogeneous and that there was no self-pollution of young clusters by core-collapse supernovae from older clusters; with a precision of 0.02 dex in relative alpha-elements abundance and 0.06 dex in oxygen abundance we would have been able to detect pollution from a single supernova, given a fortunate location of the SN and favourable conditions for ISM mixing. We estimate that the supernova rate in the Orion complex was very low, possibly producing no supernova by the time the youngest stars of the observed population formed (from around 21 to 8 Myr ago).

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“…This effect is usually small and has only been detected using high-precision abundances of solar twins. Most of the studies indicate that OCs have a uniform chemical composition of FGK main-sequence or red giant stars, at least up to ∼0.02−0.03 dex (De Silva et al 2006;Liu et al 2016b;Bovy 2016;Casamiquela et al 2020), which is below the level of the uncertainties of large spectroscopic surveys.…”

Section: Introductionmentioning

confidence: 97%

The (im)possibility of strong chemical tagging

Casamiquela

Castro-Ginard

Anders

et al. 2021

A&A

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Context. The possibility of identifying co-natal stars that have dispersed into the Galactic disc based on chemistry alone is called strong chemical tagging. It has been debated for a long time whether this is indeed feasible; it holds the promise of reconstructing the detailed star formation history of a large fraction of stars in the Galactic disc. Aims. We investigate the feasibility of strong chemical tagging using known member stars of open clusters. Methods. We analysed the largest sample of cluster members that have been homogeneously characterised with high-resolution differential abundances for 16 different elements. We also investigated the possibility of finding the known clusters in the APOGEE DR16 red clump sample with 18 chemical species. For both purposes, we used a clustering algorithm and an unsupervised dimensionality reduction technique to blindly search for groups of stars in chemical space. Results. Even if the internal coherence of the stellar abundances in the same cluster is high, typically 0.03 dex, the overlap in the chemical signatures of the clusters is large. In the sample with the highest precision and no field stars, we only recover 9 out of the 31 analysed clusters at a 40% threshold of homogeneity and precision. This ratio slightly increases when we only use clusters with 7 or more members. In the APOGEE sample, field stars are present along with four populated clusters. In this case, only one of the open clusters was moderately recovered. Conclusions. In our best-case scenario, more than 70% of the groups of stars are in fact statistical groups that contain stars belonging to different real clusters. This indicates that the chances of recovering the majority of birth clusters dissolved in the field are slim, even with the most advanced clustering techniques. We show that different stellar birth sites can have overlapping chemical signatures, even when high-resolution abundances of many different nucleosynthesis channels are used. This is substantial evidence against the possibility of strong chemical tagging. However, we can hope to recover some particular birth clusters that stand out at the edges of the chemical distribution.

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Differential abundances of open clusters and their tidal tails: Chemical tagging and chemical homogeneity

Cited by 50 publications

References 67 publications

Abundance–age relations with red clump stars in open clusters

Abundance–age relations with red clump stars in open clusters

The GALAH survey: Chemical homogeneity of the Orion complex

The (im)possibility of strong chemical tagging

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