Issue |
A&A
Volume 398, Number 1, January IV 2003
|
|
---|---|---|
Page(s) | 141 - 151 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20021615 | |
Published online | 14 January 2003 |
Vertical distribution of Galactic disk stars*
I. Kinematics and metallicity
1
Observatoire Aquitain des Sciences de l'Univers, UMR 5804, 2 rue de l'Observatoire, 33270 Floirac, France
2
Observatoire astronomique de Strasbourg, UMR 7550, Université Louis Pasteur, Strasbourg, France
Corresponding author: C. Soubiran, Caroline.Soubiran@observ.u-bordeaux.fr
Received:
3
July
2002
Accepted:
22
October
2002
Nearly 400 Tycho-2 stars have been observed in a 720 square
degree field in the direction of the North Galactic Pole with the high
resolution echelle spectrograph ELODIE. Absolute magnitudes,
effective temperatures, gravities and metallicities have been
estimated, as well as distances and 3D velocities. Most of these stars
are clump giants and span typical distances from 200 pc to 800 pc
to the galactic mid-plane. This new sample, free of any kinematical
and metallicity bias, is used to investigate the vertical distribution
of disk stars. The old thin disk and thick disk populations are
deconvolved from the velocity-metallicity distribution of the sample
and their parameters are determined. The thick disk is found to have a
moderate rotational lag of with
respect to the Sun with velocity ellipsoid
, mean
metallicity of [ Fe/H
0.05 and a high local
normalization of 15 ± 7%. Combining this NGP sample with a
local sample of giant stars from the Hipparcos catalogue, the
orientation of the velocity ellipsoid is
investigated as a function of distance to the plane and metallicity.
We find no vertex deviation for old stars, consistent with an axisymmetric
Galaxy. Paper II is devoted to the dynamical analysis of the sample,
puting new constraints on the vertical force perpendicular to the
galactic plane and on the total mass density in the galactic plane.
Key words: stars: kinematics / stars: abundances / Galaxy: disk / Galaxy: kinematics and dynamics / Galaxy: structure / Galaxy: solar neighbourhood
© ESO, 2003
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