Timing the Evolution of the Galactic Disk with NGC 6791: An Open Cluster with Peculiar High-α Chemistry as Seen by APOGEE

Linden, Sean T.; Pryal, Matthew; Hayes, Christian R.; Troup, Nicholas; Majewski, Steven R.; Andrews, Brett H.; Beers, Timothy C.; Carrera, R.; Cunha, Kátia; Fernández-Trincado, J. G.; Frinchaboy, Peter M.; Geisler, Doug; Lane, Richard R.; Nitschelm, Christian; Pan, Kaike; Prieto, C. Allende; Roman-Lopes, Alexandre; Smith, Verne V.; Sobeck, Jennifer; Tang, Baitian; Villanova, S.; Zasowski, Gail

doi:10.3847/1538-4357/aa6f17

Cited by 30 publications

(31 citation statements)

References 98 publications

(115 reference statements)

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“…We note that NGC 6791 is very metal rich, fairly old, and relatively far from the Galactic plane. Previous work using APOGEE data has suggested it likely migrated to its current location (Linden et al 2017). Since it is likely not representative of the region of the Galaxy in which it currently resides, we exclude it from further analysis.…”

Section: Ngc 6791 and The Metallicity Gradientmentioning

confidence: 98%

The Open Cluster Chemical Abundances and Mapping Survey. II. Precision Cluster Abundances for APOGEE Using SDSS DR14

Donor

Frinchaboy

Cunha

et al. 2018

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The Open Cluster Chemical Abundances and Mapping (OCCAM) survey aims to produce a comprehensive, uniform, infrared-based spectroscopic dataset for hundreds of open clusters, and to constrain key Galactic dynamical and chemical parameters from this sample. This second contribution from the OCCAM survey presents analysis of 259 member stars with [Fe/H] determinations in 19 open clusters, using Sloan Digital Sky Survey Data Release 14 (SDSS/DR14) data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and ESA Gaia. This analysis, which includes clusters with R GC ranging from 7 to 13 kpc, measures an [Fe/H] gradient of −0.061 ± 0.004 dex kpc −1 . We also confirm evidence of a significant positive gradient in the α-elements ([O/Fe], [Mg/Fe], and [Si/Fe]) and present evidence for a significant negative gradient in iron-peak elements ([Mn/Fe] and [Ni/Fe]).

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Section: Ngc 6791 and The Metallicity Gradientmentioning

confidence: 98%

The Open Cluster Chemical Abundances and Mapping Survey. II. Precision Cluster Abundances for APOGEE Using SDSS DR14

Donor

Frinchaboy

Cunha

et al. 2018

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“…On the contrary, NGC 6791 is an intriguing, old, very metal-rich, and massive system located almost 1 kpc above the Galactic plane. It has been suggested that NGC 6791 has likely migrated to its current location from its birth position (Linden et al 2017) or even has an extragalactic origin (Carraro et al 2006), although both claims are disputed. If we exclude these two clusters from the analysis, the [Fe/H] gradient flattens to −0.047 ± 0.004 dex kpc −1 .…”

Section: Galactic Trendsmentioning

confidence: 99%

Open clusters in APOGEE and GALAH

Carrera

Bragaglia

Cantat-Gaudin

et al. 2019

A&A

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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. Knowing their metallicity and possibly detailed chemical abundances is therefore important. However, 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 using publicly available catalogues of surveys in combination with Gaia data. Methods. Open cluster stars have been identified in the APOGEE and GALAH spectroscopic surveys by cross-matching their latest data releases with stars for which high-probability astrometric membership has been derived in many clusters on the basis of the Gaia second data release. Results. Radial velocities were determined for 131 and 14 clusters from APOGEE and GALAH data, respectively. This is the first radial-velocity determination from high-resolution spectra for 16 systems. Iron abundances were obtained for 90 and 14 systems from APOGEE and GALAH samples, respectively. To our knowledge 66 of these clusters (57 in APOGEE and 9 in GALAH) do not have previous determinations in the literature. For 90 and 7 clusters in the APOGEE and GALAH samples, respectively, we also determined average abundances for Na, Mg, Al, Si, Ca, Cr, Mn, and Ni.

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“…Only a few of the clusters targeted by APOGEE have tens of observed stars (e.g., NGC 2420, NGC 6791, the Pleiades, or M 67; see, e.g. Cunha et al 2015;Linden et al 2017;Souto et al 2016Souto et al , 2018. About 20 clusters include 5-30 stars each, and those are the ones we focus on in this paper.…”

Section: Datamentioning

confidence: 99%

Machine learning in APOGEE

Garcia‐Dias

Prieto

Alméida

et al. 2019

A&A

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Context. The vast volume of data generated by modern astronomical surveys offers test beds for the application of machine-learning. In these exploratory applications, it is important to evaluate potential existing tools and determine those that are optimal for extracting scientific knowledge from the available observations. Aims. We explore the possibility of using unsupervised clustering algorithms to separate stellar populations with distinct chemical patterns. Methods. Star clusters are likely the most chemically homogeneous populations in the Galaxy, and therefore any practical approach to identifying distinct stellar populations should at least be able to separate clusters from each other. We have applied eight clustering algorithms combined with four dimensionality reduction strategies to automatically distinguish stellar clusters using chemical abundances of 13 elements. Our test-bed sample includes 18 stellar clusters with a total of 453 stars. Results. We have applied statistical tests showing that some pairs of clusters (e.g., NGC 2458–NGC 2420) are indistinguishable from each other when chemical abundances from the Apache Point Galactic Evolution Experiment (APOGEE) are used. However, for most clusters we are able to automatically assign membership with metric scores similar to previous works. The confusion level of the automatically selected clusters is consistent with statistical tests that demonstrate the impossibility of perfectly distinguishing all the clusters from each other. These statistical tests and confusion levels establish a limit for the prospect of blindly identifying stars born in the same cluster based solely on chemical abundances. Conclusion. We find that some of the algorithms we explored are capable of blindly identify stellar populations with similar ages and chemical distributions in the APOGEE data. Even though we are not able to fully separate the clusters from each other, the main confusion arises from clusters with similar ages. Because some stellar clusters are chemically indistinguishable, our study supports the notion of extending weak chemical tagging that involves families of clusters instead of individual clusters.

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Timing the Evolution of the Galactic Disk with NGC 6791: An Open Cluster with Peculiar High-α Chemistry as Seen by APOGEE

Cited by 30 publications

References 98 publications

The Open Cluster Chemical Abundances and Mapping Survey. II. Precision Cluster Abundances for APOGEE Using SDSS DR14

The Open Cluster Chemical Abundances and Mapping Survey. II. Precision Cluster Abundances for APOGEE Using SDSS DR14

Open clusters in APOGEE and GALAH

Machine learning in APOGEE

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