The Stellar Age-T_eff-Kinematical Asymmetry in the Solar Neighborhood from LAMOST

Abstract

With the velocity de-projection technique, we derived the averaged 3 dimensional local velocity distribution using only the line-of-sight velocity for the 200,000 FGK type main-sequence stars from the LAMOST DR1 data. Taking the effective temperature as a proxy for age, we investigate the variation of the velocity distribution as a function of T_eff and disk height within 100 < |z| < 500 pc. Using the mean velocities of the cool stars, we derive the solar motion of (U_⊙, V_⊙, W_⊙)=(9.58±2.39, 10.52±1.96, 7.01±1.67) kms⁻¹ with respect to the local standard of rest (LSR). Moreover, we find that the stars with T_eff > 6000 K show a net asymmetric motion of 〈U〉~2 kms⁻¹ and 〈W〉~3 kms⁻¹ compared to the stars with T_eff < 6000 K. And their azimuthal velocity increases when |z| increases. The asymmetric motion in the warmer stars is likely because they are too young and not completely relaxed.