On the correlation of elemental abundances with kinematics among galactic disk stars

Free access article

Issue		A&A Volume 418, Number 2, May I 2004


Page(s)		551 - 562
Section		Galactic structure, stellar clusters and populations
DOI		http://dx.doi.org/10.1051/0004-6361:20034454

A&A 418, 551-562 (2004)
DOI: 10.1051/0004-6361:20034454

On the correlation of elemental abundances with kinematics among galactic disk stars

T. V. Mishenina¹, C. Soubiran², V. V. Kovtyukh¹ and S. A. Korotin¹

¹ Astronomical Observatory of Odessa National University and Isaac Newton Institute of Chile, Odessa Branch, Ukraine
² Observatoire Aquitain des Sciences de l'Univers, CNRS UMR 5804, BP 89, 33270 Floirac, France

(Received 6 October 2003 / Accepted 27 January 2004 )

Abstract
We have performed the detailed analysis of 174 high-resolution spectra of FGK dwarfs obtained with the ELODIE echelle spectrograph at the Observatoire de Haute-Provence. Abundances of Fe, Si and Ni have been determined from equivalent widths under LTE approximation, whereas abundances of Mg have been determined under NLTE approximation using equivalent widths of 4 lines and profiles of 5 lines. Spatial velocities with an accuracy better than 1 $\mathrm{~km\,s}^{-1}$ , as well as orbits, have been computed for all stars. They have been used to define 2 subsamples kinematically representative of the thin disk and the thick disk in order to highlight their respective properties. A transition occurs at [Fe/H] =-0.3. Stars more metal-rich than this value have a flat distribution with ${Z_{\rm max}}$ $\;<1$ kpc and $\sigma_W<20$ $\mathrm{~km\,s}^{-1}$ , and a narrow distribution of $[\alpha/\mathrm{Fe}]$ . There exist stars in this metallicity regime which cannot belong to the thin disk because of their excentric orbits, neither to the thick disk because of their low scale height. Several thin disk stars are identified down to [Fe/H] =-0.80. Their Mg enrichment is lower than thick disk stars with the same metallicity. We confirm from a larger sample the results of Feltzing et al. (2003) and Bensby et al. (2003) showing a decrease of [ $\alpha$ /Fe] with [Fe/H] in the thick disk interpreted as the signature of the SNIa which have progressively enriched the ISM with iron. However our data suggest that the star formation in the thick disk stopped when the enrichment was [Fe/H] =-0.30, [Mg/Fe] =+0.20, [Si/Fe] =+0.17. A vertical gradient in [ $\alpha$ /Fe] may exist in the thick disk but should be confirmed with a larger sample. Finally we have identified 2 new candidates of the HR1614 moving group.

Key words: stars: fundamental parameters -- stars: abundances -- stars: kinematics -- stars: atmospheres -- Galaxy: stellar content

Offprint request: T. V. Mishenina, tamar@deneb.odessa.ua

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