J/A+A/629/A34ivo://CDS.VizieR/J/A+A/629/A34doi:10.26093/cds/vizier.36290034CDSGarcia-Dias R.Allende Prieto C.Sanchez Almeida J.Alonso Palicio P.2019-11-27T13:36:24Z2019-09-02T08:14:07ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frglobular-star-clustersopen-star-clustersThe vast volume of data generated by modern astronomical surveys offer test beds for the application of machine learning. In these exploratory applications, it is important to evaluate potential existing tools and determine which ones are optimal to extract scientific knowledge from the available observations. This work aims to explore the possibility of using unsupervised clustering algorithms to separate stellar populations with distinct chemical patterns. Star clusters are likely the most chemically homogeneous populations in the Galaxy, and therefore any practical approach to identify 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 discriminate automatically stellar clusters using chemical abundances of 13 elements. Our test-bed sample includes 18 stellar clusters with a total of 453 stars. We have applied statistical tests showing that some pairs of clusters (e.g., NGC 2458-NGC 2420) are indistinguishable from each other when using the Apache Point Galactic Evolution Experiment (APOGEE) chemical abundances. 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 discriminating 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. We find that some of the algorithms 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. Since there are stellar clusters that are chemically indistinguishable, our study supports the notion of extending weak chemical tagging involving families of clusters instead of individual clusters.2019A&A...629A..34Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/629/A34CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/629/A34https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/629/A34http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/629/A34https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/629/A34https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/629/A34http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/629/A34GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/629/A34/table1 (Initial list of stars used in the article)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/629/A34/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/629/A34/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/629/A34/table1?GETtext/xml+votable180.050000true80.121041730.54483330.0055555555555555565/115 118 792 1019 1074 3688 6/484-485 496-497 1512 1514 1782-1783 1788-1789 3062-3063 3089 3091-3092 3094 3277 3611 3633 3636 4073 4075 4253 4255 4277 4320-4321 4783 6148-6149 9436 9664 9666 10321 10336-10337 12405 12943 14173 14175 14197 14573 14575 15121 15417 19091 20562 23861 24344-24345 24376 24491 24500 24502 27975 27981 27986 27992 28067 30769 31416-31417https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/629/A34?format=asciidefaultJ/A+A/629/A34/table1Initial list of stars used in the articlerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAPOGEEID from APOGEE survey (2MHHMMSSss+DDMMSSs)meta.id;meta.maincharClusterCluster for which the star is a member (1)meta.id.parentchar_RAPosition from APOGEE name (right ascension part)degpos.eq.ra;meta.main_DEPosition from APOGEE name (declination part)degpos.eq.dec;meta.main