Kinematics and velocity ellipsoid of the F giants

Abstract

To study the kinematics of the F giant stars (luminosity class III), proper motions taken from van Leeuwen’s new reduction of the Hipparcos catalogue are used. 591 stars, of which 222 have radial velocities, were used in the final study. Semi-definite programming solves for the kinematical parameters such as the Oort constants and simultaneously for the coefficients of the velocity ellipsoid. The condition that the solution for the solar velocity calculated both from the kinematical parameters and from the velocity ellipsoid calculation should be the same is enforced. The truncated singular value decomposition allows one to incorporate into the velocity ellipsoid determination tangential velocities for which there are no corresponding radial velocities. The solution gives solar velocity of 18.52 ± 0.48 km s−1 ; Oort’s constants, in units of km s−1 kpc−1, A = 14.85 ± 7.47 and B = −10.85 ± 6.83, implying a rotational velocity of 210.68 ± 29.66 km s−1 if we take the distance to the Galactic Centre as 8.2 ± 1.1 kpc; velocity dispersions, in units of km s−1, of σx = 36.89 ± 1.90, σy = 24.66 ± 1.16, σz = 17.97 ± 0.81 with a vertex deviation of −16. ◦54 ± 14. ◦88.