Book contents
- Frontmatter
- Contents
- List of contributors
- Preface
- Part I Abundances in the Galaxy: field stars
- 1 Metal-rich stars and stellar populations: a brief history and new results
- 2 The metal-rich nature of stars with planets
- 3 Solar chemical peculiarities?
- 4 Kinematics of metal-rich stars with and without planets
- 5 Elemental abundance trends in the metal-rich thin and thick disks
- 6 Metal-rich massive stars: how metal-rich are they?
- 7 Hercules-stream stars and the metal-rich thick disk
- 8 An abundance survey of the Galactic thick disk
- Part II Abundances in the Galaxy: Galactic stars in clusters, bulges and the centre
- Part III Observations – abundances in extragalactic contexts
- Part IV Stellar populations and mass functions
- Part V Physical processes at high metallicity
- Part VI Formation and evolution of metal-rich stars and stellar yields
- Part VII Chemical and photometric evolution beyond Solar metallicity
8 - An abundance survey of the Galactic thick disk
Published online by Cambridge University Press: 02 December 2009
- Frontmatter
- Contents
- List of contributors
- Preface
- Part I Abundances in the Galaxy: field stars
- 1 Metal-rich stars and stellar populations: a brief history and new results
- 2 The metal-rich nature of stars with planets
- 3 Solar chemical peculiarities?
- 4 Kinematics of metal-rich stars with and without planets
- 5 Elemental abundance trends in the metal-rich thin and thick disks
- 6 Metal-rich massive stars: how metal-rich are they?
- 7 Hercules-stream stars and the metal-rich thick disk
- 8 An abundance survey of the Galactic thick disk
- Part II Abundances in the Galaxy: Galactic stars in clusters, bulges and the centre
- Part III Observations – abundances in extragalactic contexts
- Part IV Stellar populations and mass functions
- Part V Physical processes at high metallicity
- Part VI Formation and evolution of metal-rich stars and stellar yields
- Part VII Chemical and photometric evolution beyond Solar metallicity
Summary
We present the results of our recent abundance survey of the Galactic thick disk. We selected from the Hipparcos catalog 176 sample stars satisfying the following criteria: they are nearby (d ≤ 150 pc) subgiants and dwarfs, of spectral types F and G, and with thick-disk kinematics (VLSR ≤ −40 kms−1, │WLSR│ ≤ 30 kms−1). Assuming that the velocity distribution of each stellar population is Gaussian, we assigned stars with a probability P ≤ 70% to one of the three components. This resulted in 95 thick-disk stars, 17 thin-disk stars, and 24 halo stars. The remaining 40 objects cannot be unambiguously assigned to one of the three components.
We derived abundances for 23 elements from C to Eu. The thick-disk abundance patterns are compared with earlier results from the thin-disk survey of Reddy et al. (2003). The levels of α-elements (O, Mg, Si, Ca, and Ti), thought to be produced dominantly in Type-ii supernovae, are enhanced in thick-disk stars relative to the values found for thin-disk members in the range −0.3 > [Fe/H] > −1.2. The scatter in the abundance ratios [X/Fe] at a given [Fe/H] for thick-disk stars is consistent with the predicted dispersion due to measurement errors, as is the case for the thin disk, suggesting a lack of “cosmic” scatter. The observed compositions seem consistent with a model of galaxy formation by mergers in a ∧ CDM universe.
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- The Metal-Rich Universe , pp. 69 - 74Publisher: Cambridge University PressPrint publication year: 2008