Astronomy and Astrophysics, volume 480, 91-101 (2008/3-2)
Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants.
SOUBIRAN C., BIENAYME O., MISHENINA T.V. and KOVTYUKH V.V.
Abstract (from CDS):
We present the parameters of 891 stars, mostly clump giants, including atmospheric parameters, distances, absolute magnitudes, spatial velocities, galactic orbits and ages. One part of this sample consists of local giants, within 100pc, with atmospheric parameters either estimated from our spectroscopic observations at high resolution and high signal-to-noise ratio, or retrieved from the literature. The other part of the sample includes 523 distant stars, spanning distances up to 1 kpc in the direction of the North Galactic Pole, for which we have estimated atmospheric parameters from high resolution but low signal-to-noise Echelle spectra. This new sample is kinematically unbiased, with well-defined boundaries in magnitude and colours. We revisit the basic properties of the Galactic thin disk as traced by clump giants. We find the metallicity distribution to be different from that of dwarfs, with fewer metal-rich stars. We find evidence for a vertical metallicity gradient of -0.31dex/kpc and for a transition at ∼4-5Gyr in both the metallicity and velocities. The age-metallicity relation (AMR), which exhibits a very low dispersion, increases smoothly from 10 to 4Gyr, with a steeper increase for younger stars. The age-velocity relation (AVR) is characterized by the saturation of the V and W dispersions at 5Gyr, and continuous heating in U.
stars: kinematics - stars: fundamental parameters - Galaxy: disk - Galaxy: structure - solar neighbourhood
VizieR on-line data:
<Available at CDS (J/A+A/480/91): table1.dat table2.dat>
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