Issue |
A&A
Volume 418, Number 3, May II 2004
|
|
---|---|---|
Page(s) | 989 - 1019 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20035959 | |
Published online | 16 April 2004 |
The Geneva-Copenhagen survey of the Solar neighbourhood *,**
Ages, metallicities, and kinematic properties of ~14 000 F and G dwarfs
1
Niels Bohr Institute for Astronomy, Physics & Geophysics, Blegdamsvej 17, 2100 Copenhagen, Denmark
2
Lund Observatory, Box 43, 22100 Lund, Sweden
3
Observatoire de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
4
Astronomical Observatory, NBIfAFG, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
5
Nordic Optical Telescope Scientific Association, Apartado 474, 38700 Santa Cruz de La Palma, Spain
Corresponding author: B. Nordström, birgitta@astro.ku.dk
Received:
31
December
2003
Accepted:
23
January
2004
We present and discuss new determinations of metallicity, rotation,
age, kinematics, and Galactic orbits for a complete, magnitude-limited, and
kinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our ~63 000 new, accurate radial-velocity observations for nearly 13 500 stars
allow identification of most of the binary stars in the sample and, together
with published photometry, Hipparcos parallaxes, Tycho-2 proper
motions, and a few earlier radial velocities, complete the kinematic
information for 14 139 stars. These high-quality velocity data are supplemented
by effective temperatures and metallicities newly derived from recent and/or
revised calibrations. The remaining stars either lack Hipparcos data or have
fast rotation.
A major effort has been devoted to the determination of new isochrone ages for
all stars for which this is possible. Particular attention has been given to a
realistic treatment of statistical biases and error estimates, as standard
techniques tend to underestimate these effects and introduce spurious features
in the age distributions. Our ages agree well with those by Edvardsson et al.
([CITE]), despite several astrophysical and computational improvements
since then. We demonstrate, however, how strong observational and theoretical
biases cause the distribution of the observed ages to be very different
from that of the true age distribution of the sample.
Among the many basic relations of the Galactic disk that can be reinvestigated
from the data presented here, we revisit the metallicity distribution of the G
dwarfs and the age-metallicity, age-velocity, and metallicity-velocity
relations of the Solar neighbourhood. Our first results confirm the lack of
metal-poor G dwarfs relative to closed-box model predictions (the “G dwarf
problem”), the existence of radial metallicity gradients in the disk, the
small change in mean metallicity of the thin disk since its formation and the
substantial scatter in metallicity at all ages, and the continuing kinematic
heating of the thin disk with an efficiency consistent with that expected for a
combination of spiral arms and giant molecular clouds. Distinct features in the
distribution of the V component of the space motion are extended in age and
metallicity, corresponding to the effects of stochastic spiral waves rather
than classical moving groups, and may complicate the identification of
thick-disk stars from kinematic criteria. More advanced analyses of this rich
material will require careful simulations of the selection criteria for the
sample and the distribution of observational errors.
Key words: Galaxy: disk / Galaxy: solar neighbourhood / Galaxy: stellar content / Galaxy: kinematics and dynamics / Galaxy: evolution / stars: fundamental parameters
© ESO, 2004
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