Kinematics of nearby subdwarf stars

Free access article

Issue		A&A Volume 433, Number 3, April III 2005


Page(s)		911 - 916
Section		Galactic structure, stellar clusters and populations
DOI		http://dx.doi.org/10.1051/0004-6361:20035829

A&A 433, 911-916 (2005)
DOI: 10.1051/0004-6361:20035829

Kinematics of nearby subdwarf stars

M. I. Arifyanto, B. Fuchs, H. Jahreiß and R. Wielen

Astronomisches Rechen-Institut, Mönchhofstraße 12-14, 69120 Heidelberg, Germany
e-mail: arifyanto@ari.uni-heidelberg.de

(Received 9 December 2003 / Accepted 10 December 2004)

Abstract
We present an analysis of the space motions of 742 subdwarf stars based on the sample of Carney et al. (1994, AJ, 107, 22 40). Hipparcos parallaxes, TYC2+HIP proper motions and Tycho 2 proper motions were combined with radial velocities and metallicities from CLLA. The kinematical behavior is discussed in particular in relation to their metallicities. The majority of these sample stars have metal abundances of [Fe/H] >-1 and represent the thick disk population. The halo component, with [Fe/H] <-1.6, is characterized by a low mean rotation velocity and a radially elongated velocity ellipsoid. In the intermediate metallicity range ( $-1.6\leq$ [Fe/H] $\leq-1$ ), we find a significant number of subdwarfs with disklike kinematics. We interpret this population of stars as a metal-weak thick disk (MWTD) population.

Key words: stars: subdwarfs -- Galaxy: kinematics and dynamics -- Galaxy: solar neighbourhood

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