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The GALAH survey: chemical tagging of star clusters and new members in the Pleiades
Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia..
Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia..
Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
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2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 4, p. 4612-4633Article in journal (Refereed) Published
Abstract [en]

The technique of chemical tagging uses the elemental abundances of stellar atmospheres to 'reconstruct' chemically homogeneous star clusters that have long since dispersed. The GALAH spectroscopic survey - which aims to observe one million stars using the Anglo-Australian Telescope - allows us to measure up to 30 elements or dimensions in the stellar chemical abundance space, many of which are not independent. How to find clustering reliably in a noisy high-dimensional space is a difficult problem that remains largely unsolved. Here, we explore t-distributed stochastic neighbour embedding (t-SNE) - which identifies an optimal mapping of a high-dimensional space into fewer dimensions - whilst conserving the original clustering information. Typically, the projection is made to a 2D space to aid recognition of clusters by eye. We show that this method is a reliable tool for chemical tagging because it can: (i) resolve clustering in chemical space alone, (ii) recover known open and globular clusters with high efficiency and low contamination, and (iii) relate field stars to known clusters. t-SNE also provides a useful visualization of a high-dimensional space. We demonstrate the method on a data set of 13 abundances measured in the spectra of 187 000 stars by the GALAH survey. We recover seven of the nine observed clusters (six globular and three open clusters) in chemical space with minimal contamination from field stars and low numbers of outliers. With chemical tagging, we also identify two Pleiades supercluster members (which we confirm kinematically), one as far as 6 degrees-one tidal radius away from the cluster centre.

Place, publisher, year, edition, pages
Oxford University Press, 2018. Vol. 473, no 4, p. 4612-4633
Keywords [en]
methods: data analysis, stars: abundances, open clusters and associations: general, open clusters and associations: individual: Pleiades
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-346887DOI: 10.1093/mnras/stx2637ISI: 000424117300024OAI: oai:DiVA.org:uu-346887DiVA, id: diva2:1194062
Funder
Australian Research Council, DE140100598, FT110100793, DP150104667Available from: 2018-03-28 Created: 2018-03-28 Last updated: 2018-03-28Bibliographically approved

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Lind, Karin

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