CHEMICAL TAGGING CAN WORK: IDENTIFICATION OF STELLAR PHASE-SPACE STRUCTURES PURELY BY CHEMICAL-ABUNDANCE SIMILARITY

By David W. Hogg, A. Casey, M. Ness, Hans-Walter Rix, Daniel Foreman-Mackey, S. Hasselquist, A. Ho, J. Holtzman, S. Majewski, S. Martell and 3 more. 2016

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Chemical tagging promises to use detailed abundance measurements to identify spatially separated stars that were, in fact, born together (in the same molecular cloud) long ago. This idea has not yielded much practical success, presumably because of the noise and incompleteness in chemical-abundance measurements. We have succeeded in substantially improving spectroscopic measurements with The Cannon, which has now delivered 15 individual abundances for stars observed as part of the APOGEE spectroscopic survey, with precisions around 0.04 dex. We test the chemical-tagging hypothesis by looking at clusters in abundance space and confirming that they are clustered in phase space. We identify (by the k-means algorithm) overdensities of stars in the 15-dimensional chemical-abundance space delivered by The Cannon, and plot the associated stars in phase space. We use only abundance-space information (no positional information) to identify stellar groups. We find that clusters in abundance space are indeed clusters in phase space, and we recover some known phase-space clusters and find other interesting structures. This is the first-ever project to identify phase-space structures at the survey-scale by blind search purely in abundance space; it verifies the precision of the abundance measurements delivered by The Cannon; the prospects for future data sets appear very good.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Yule-Simpson’s paradox in Galactic Archaeology (2019, methodology): “Galactic Archaeologists use the observed stellar kinematics, chemical abundances, and derived ages as fossil records to recover the chemo-dynamical history of the Milky Way (Freeman & Bland-Hawthorn 2002; Bland-Hawthorn et al. 2010; Rix & Bovy 2013; Binney 2013; Minchev 2016; Hogg et al. 2016).”
Dynamical modelling of the galactic bulge and bar: the Milky Way's pattern speed, stellar and dark matter mass distribution (2016, background): “By looking at clumps in chemical space, Hogg et al. (2016) already found evidence for a very young stellar component that may correspond to the superthin bar of W15.”