Stellar Population Astrophysics (SPA) with TNG

Zhang, R.; Lucatello, S.; Bragaglia, A.; Carrera, R.; Spina, L.; Alonso-Santiago, J.; Andreuzzi, G.; Casali, G.; Carretta, E.; Frasca, A.; Fu, X.; Magrini, L.; Origlia, L.; D’Orazi, V.; Vallenari, A.

doi:10.1051/0004-6361/202141188

Cited by 24 publications

(22 citation statements)

References 75 publications

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“…Similar cases have been recently reported in the literature (e.g. Baratella et al 2020;Zhang et al 2021), where clusters with relatively young ages show large discrepancies when compared to chemical models, with metallicities that are too low for their Galactocentric positions. One of the hypotheses for this is the difficulty in deriving abundances for young stars due to their chromospheric activity and magnetic fields.…”

Section: Chemical Abundancessupporting

confidence: 89%

“…In fact, it is known that the slope of the gradient changes with age, being steeper for the oldest clusters (e.g. Friel et al 2002;Carrera & Pancino 2011;Donati et al 2015;Donor et al 2020a;Zhang et al 2021). For this reason, in the rest of the panels of Fig.…”

Section: Open Clusters Radial Gradientmentioning

confidence: 93%

“…Additionally, Kovtyukh (2007) also determined the effective temperature for the star 2015663649928489856 in NGC 7654 (6268±149 k), which again is in agreement with our value within the uncertainties. Additionally, the sampled star in Gulliver 37 has been recently analysed by Zhang et al (2021). We excluded this object from our analysis because it was reported as a variable in the literature (Mermilliod et al 2008b).…”

Section: Atmospheric Parametersmentioning

confidence: 99%

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One Star to Tag Them All (OSTTA): I. Radial velocities and chemical abundances for 20 poorly studied open clusters

Carrera,

Casamiquela,

Bragaglia

et al. 2022

Preprint

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Context. Open clusters are ideal laboratories to investigate a variety of astrophysical topics, from the properties of the Galactic disc to stellar evolution models. For this purpose, we need to know their chemical composition in detail. Unfortunately, the number of systems with chemical abundances determined from high resolution spectroscopy remains small. Aims. Our aim is to increase the number of open clusters with radial velocities and chemical abundances determined from high resolution spectroscopy by sampling a few stars in clusters which had not been previously studied. Methods. We obtained high resolution spectra with the FIbre-fed Echelle Spectrograph (FIES) at Nordic Optical Telescope (NOT) for 41 stars belonging to 20 open clusters. These stars have high astrometric membership probabilities determined from the Gaia second data release. Results. We derived radial velocites for all the observed stars which were used to confirm their membership to the corresponding clusters. For Gulliver 37, we cannot be sure the observed star is a real member. We derived atmospheric parameters for the 32 stars considered to be real cluster members. We discarded five stars because they have very low gravity or their atmospheric parameters were not properly constrained due to low signal-to-noise ratio spectra. Therefore, detailed chemical abundances were determined for 28 stars belonging to 17 clusters. For most of them, this is the first chemical analysis available in the literature. Finally, we compared the clusters in our sample to a large population of well-studied clusters. The studied systems follow the trends, both chemical and kinematical, described by the majority of open clusters. It is worth mentioning that the three most metal-poor studied clusters (NGC 1027, NGC 1750, and Trumpler 2) are enhanced in Si, but not in the other α-elements studied (Mg, Ca, and Ti).

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Section: Chemical Abundancessupporting

confidence: 89%

Section: Open Clusters Radial Gradientmentioning

confidence: 93%

Section: Atmospheric Parametersmentioning

confidence: 99%

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One Star to Tag Them All (OSTTA): I. Radial velocities and chemical abundances for 20 poorly studied open clusters

Carrera,

Casamiquela,

Bragaglia

et al. 2022

Preprint

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“…We initially targeted the giants to determine the cluster metallicity and detailed abundances, as we did for other clusters in SPA. We mainly selected red clump stars for this so that the sample would be as homogeneous as possible (see Casali et al 2020;Zhang et al 2021). These stars, orange circles in Fig.…”

Section: Observations and Target Selectionmentioning

confidence: 99%

Stellar Population Astrophysics (SPA) with the TNG

Alonso-Santiago

Frasca

Catanzaro

et al. 2021

A&A

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Stock 2 is a little-studied open cluster that shows an extended main-sequence turnoff (eMSTO). In order to investigate this phenomenon and characterise the cluster itself, we performed high-resolution spectroscopy in the framework of the Stellar Population Astrophysics project. We employed the High Accuracy Radial velocity Planet Searcher in the Northern hemisphere spectrograph at the Telescopio Nazionale Galileo (TNG). We completed our observations with additional spectra taken with the Catania Astrophysical Observatory Spectropolarimeter. We observed 46 stars (dwarfs and giants). They represent by far the largest sample collected for this cluster to date. We provide the stellar parameters, the extinction, and the radial and projected rotational velocities for most of the stars. Chemical abundances for 21 species with atomic numbers up to 56 have also been derived. We note a differential reddening in the cluster field with an average value of 0.27 mag. This appears the main cause for the observed eMSTO because it cannot be explained as the result of different rotational velocities, as found in other clusters. We estimate an age for Stock 2 of 450 ± 150 Ma, which corresponds to a MSTO stellar mass of ≈2.8 M⊙. The cluster mean radial velocity is about 8.0 km s−1. We find a solar-like metallicity for the cluster, [Fe/H] = −0.07 ± 0.06, compatible with its galactocentric distance. The chemical abundances of main-sequence stars and giants are compatible within the errors. The exceptions are barium and strontium, which are clearly overabundant in giants, and cobalt, which is only marginally overabundant. Finally, the chemical composition of Stock 2 is fully compatible with the composition observed in other open clusters of the Galactic thin-disc population.

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“…From these cluster members we discard the stars in clusters younger than 500 Myr. This is necessary because chemical abundances in younger clusters suffer of low accuracy as their metal content appears significantly lower than what it actually is depending on the level of stellar chromospheric activity (Yana Galarza et al 2019;Baratella et al 2020Baratella et al , 2021Spina et al 2020;Zhang et al 2021). Therefore, after this further selection we count 306 stars in open clusters.…”

Section: Data Setmentioning

confidence: 99%

The Gaia-ESO Survey: Chemical tagging in the thin disk. Open clusters blindly recovered in the elemental abundance space

Spina¹,

Magrini²,

Sacco³

et al. 2022

Preprint

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Context. The chemical makeup of a star provides the fossil information of the environment where it formed. Under this premise, it should be possible to use chemical abundances to tag stars that formed within the same stellar association. This idea -known as chemical tagging -has not produced the expected results, especially within the thin disk where open stellar clusters have chemical patterns that are difficult to disentangle. Aims. The ultimate goal of this study is to probe the feasibility of chemical tagging within the thin disk population using high-quality data from a controlled sample of stars. We also aim at improving the existing techniques of chemical tagging and giving some kind of guidance on different strategies of clustering analysis in the elemental abundance space. Methods. Here we develop the first blind search of open clusters' members through clustering analysis in the elemental abundance space using the OPTICS algorithm applied to data from the Gaia-ESO survey. First, we evaluate different strategies of analysis (e.g., choice of the algorithm, data preprocessing techniques, metric, space of data clustering), determining which ones are more performing. Second, we apply these methods to a data set including both field stars and open clusters attempting a blind recover of as many open clusters as possible. Results. We show how specific strategies of data analysis can improve the final results. Specifically, we demonstrate that open clusters can be more efficaciously recovered with the Manhattan metric and on a space whose dimensions are carefully selected. Using these (and other) prescriptions we are able to recover open clusters hidden in our data set and find new members of these stellar associations (i.e., escapers, binaries). Conclusions. Our results indicate that there are chances of recovering open clusters' members via clustering analysis in the elemental abundance space, albeit in a data set that has a very high fraction of cluster members compared to an average field star sample. Presumably, the performances of chemical tagging will further increase with higher quality data and more sophisticated clustering algorithms, which will likely became available in the near future.

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Stellar Population Astrophysics (SPA) with TNG

Cited by 24 publications

References 75 publications

One Star to Tag Them All (OSTTA): I. Radial velocities and chemical abundances for 20 poorly studied open clusters

One Star to Tag Them All (OSTTA): I. Radial velocities and chemical abundances for 20 poorly studied open clusters

Stellar Population Astrophysics (SPA) with the TNG

The Gaia-ESO Survey: Chemical tagging in the thin disk. Open clusters blindly recovered in the elemental abundance space

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