Local kinematics of dwarfs from the Tycho-2 data

Abstract

The stellar velocity field of about 70000 dwarfs within 2 kps from the Sun is investigated from the "Tycho-2" data and known MK spectral classification. The Ogorodnikov-Milne model of a three-dimensional differential velocity field is used. The generalized Oort constants and components of the solar motion with respect to various spectral groups are determined. It is shown that the Oort-Lindblad model with parameters B, A', K, φ is sufficient to describe the galactic global rotation of dwarfs. The effects associated with K and φ parameters are detected for early type stars. The shape and orientation of the velocity ellipsoid are determined as a function of stellar spectral class.