More pieces of the puzzle: Chemistry and substructures in the Galactic thick disk

Abstract

We present a study of the chemical abundances of Solar neighbourhood stars associated to dynamical structures in the Milky Way's (thick) disk. These stars were identified as overdensity in the eccentricity range 0.3< ecc < 0.5 in the Copenhagen-Geneva Survey by Helmi et al. (2006). We find that the stars with these dynamical characteristics do not constitute a homogeneous population. A relatively sharp transition in dynamical and chemical properties appears to occur at a metallicity of [Fe/H] ~ -0.4. Stars with [Fe/H] > -0.4 have mostly lower eccentricities, smaller vertical velocity dispersions, are alpha-enhanced and define a rather narrow sequence in [alpha/Fe] vs [Fe/H], clearly distinct from that of the thin disk. Stars with [Fe/H] < -0.4 have a range of eccentricities, are hotter vertically, and depict a larger spread in [alpha/Fe]. We have also found tentative evidence of substructure possibly associated to the disruption of a metal-rich star cluster. The differences between these populations of stars is also present in e.g. [Zn/Fe], [Ni/Fe] and [SmII/Fe], suggesting a real physical distinction.

Astrophysical Journal in press. 5 pages, 4 figures

References in corpus (8)

• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• alpha-, r-, and s-process element trends in the Galactic thin and thick disks
• DAOSPEC: an automatic code for measuring equivalent widths in high-resolution stellar spectra
• The Gaia-ESO Survey: the Galactic Thick to Thin Disc transition
• Radial mixing and the transition between the thick and thin Galactic discs
• Chemically Tagging the HR1614 Moving Group
• The Nature and Origin of Substructure in the Outskirts of M31. I. Surveying the Stellar Content with HST/ACS
• Stellar substructures in the solar neighbourhood. I. Kinematic group 3 in the Geneva-Copenhagen survey

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