uvby-β photometry and kinematics of metal-poor stars: A search for moving groups in the Galactic stellar halo

Abstract

The possible presence of moving groups in the local Galactic stellar halo has been examined based on new uvby-β photometry for a sample of 143 metal-poor stars joined to the photometry of 1553 stars from the previous catalogues of Schuster & Nissen (1988), Schuster et al. (1993), and Schuster et al. (2006). This new set of photometric data, together with radial velocities and proper motions taken from the literature, have allowed us to obtain Galactic space velocities U',V', and W' for nearly the entire sample. With this kinematic information, three diagrams: the [Fe/H] vs V_rot, the Bottlinger (V’ vs U’) and the Toomre (V’ vs (U’²+W’²)^1/2) have been obtained and used to identify probable groups of stars in common between them. Once identified, these groups were compared to moving groups reported in the literature. In particular, probable members of the Kapteyn group and ω Cen were identified.