Kinematics of Nearby Subdwarfs

A sample of subdwarfs with accurate space velocities and stan-darized metallicities is presented. This was constructed by combining Hip-parcos parallaxes and proper motions with radial velocities and metallicities from Carney et al. (1994; CLLA). The accurate Hipparcos parallaxes lead to an-upward-correction factor of 11% of the photometric distance scale of CLLA. The kinematical behaviour of the subdwarfs is discussed in particular in relation to their metallicities. Most of the stars turn out to be thick disk stars, but the sample contains also many genuine halo stars. While the extreme metal poor halo does not rotate, a population of subdwarfs with metallicities in the range –1.6 < [Fe/H] < –1.0 dex appears to rotate around the galactic center with a mean rotation speed of about 100 km/s. The data material, which we have analyzed, is based on the sample of high proper motion stars by Carney et al. (1994; CLLA). CLLA have measured photometric parallaxes, radial velocities, and metallicities of most of the A to early G stars, many late G and some early K stars in the Lowell Proper Motion Catalogue. This data set of 1464 stars has been cross-identified with the Hipparcos catalogue (ESA 1997) and we found 767 stars in common. However, the sample had to be cleaned under various aspects. For instance, for some stars not all data were available or some Hipparcos parallaxes were not accurate enough. In Fig. 1 the colour-magnitude diagram of the remaining stars is shown. Despite the efforts of CLLA to avoid them the sample is still contaminated by giants and subgiants, which can be detected now due to the improved accuracies of the absolute magnitudes. We have removed all stars lying above a line in the CMD defined by the zero age