t-SNE as a tool for studying clustering in the elemental abundance space

One of the main motivations for the GALAH survey is to measure abundances of many elements in sufficiently large number of stars that some of them can be identified as stars that were born in the same cluster but all indications of this fact have been lost, except for the chemical fingerprint. Chemical tagging can reveal the connection between such stars, but state of the art observations and analytical methods will be needed to actually perform this task.

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Reconstructing Fossil Sub-structures of the Galactic Disk: Clues from Abundance Patterns of Old Open Clusters and Moving Groups

The long term goal of large-scale chemical tagging is to use stellar elemental abundances as a tracer of dispersed substructures of the Galactic disk. The identification of such lost stellar aggregates and the exploration of their chemical properties will be key in understanding the formation and evolution of the disk. Present day stellar structures such as open clusters and moving groups are the ideal testing grounds for the viability of chemical tagging, as they are believed to be the remnants of the original larger star-forming aggregates.

Chemical Homogeneity in Collinder 261 and Implications for Chemical Tagging

This paper presents abundances for 12 red giants of the old open cluster Collinder 261 based on spectra from the Very Large Telescope UVES. Abundances were derived for Na, Mg, Si, Ca, Mn, Fe, Ni, Zr, and Ba. We find that the cluster has a solar-level metallicity of [Fe/H]=-0.03 dex. However, most α- and s-process elements were found to be enhanced. The star-to-star scatter was consistent with the expected measurement uncertainty for all elements. The observed rms scatter is as follows: Na=0.07, Mg=0.05, Si=0.06, Ca=0.05, Mn=0.03, Fe=0.02, Ni=0.04, Zr=0.12, and Ba=0.03 dex.

Chemical Homogeneity in the Hyades

We present an abundance analysis of the heavy elements Zr, Ba, La, Ce, and Nd for Hyades F-K dwarfs based on high-resolution, high signal-to-noise ratio spectra from Keck HIRES. The derived abundances show the stellar members to be highly uniform, although some elements show a small residual trend with temperature. The rms scatter for each element for the cluster members is as follows: Zr=0.055, Ba=0.049, Ce=0.025, La=0.025, and Nd=0.032 dex. This is consistent with the measurement errors and implies that there is little or no intrinsic scatter among the Hyades members.

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