TY - JOUR
T1 - The GALAH survey
T2 - Chemical tagging of star clusters and new members in the Pleiades
AU - Kos, Janez
AU - Bland-Hawthorn, Joss
AU - Freeman, Ken
AU - Buder, Sven
AU - Traven, Gregor
AU - De Silva, Gayandhi M.
AU - Sharma, Sanjib
AU - Asplund, Martin
AU - Duong, Ly
AU - Lin, Jane
AU - Lind, Karin
AU - Martell, Sarah
AU - Simpson, Jeffrey D.
AU - Stello, Dennis
AU - Zucker, Daniel B.
AU - Zwitter, Tomaž
AU - Anguiano, Borja
AU - Costa, Gary Da
AU - D'Orazi, Valentina
AU - Horner, Jonathan
AU - Kafle, Prajwal R.
AU - Lewis, Geraint
AU - Munari, Ulisse
AU - Nataf, David M.
AU - Ness, Melissa
AU - Reid, Warren
AU - Schlesinger, Katie
AU - Ting, Yuan Sen
AU - Wyse, Rosemary
PY - 2018/1/1
Y1 - 2018/1/1
N2 - 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° - one tidal radius away from the cluster centre.
AB - 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° - one tidal radius away from the cluster centre.
KW - Methods: data analysis
KW - Open clusters and associations: general
KW - Open clusters and associations: individual: Pleiades
KW - Stars: abundances
UR - http://www.scopus.com/inward/record.url?scp=85045770025&partnerID=8YFLogxK
U2 - 10.1093/mnras/stx2637
DO - 10.1093/mnras/stx2637
M3 - Article
AN - SCOPUS:85045770025
SN - 0035-8711
VL - 473
SP - 4612
EP - 4633
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -