Tracing the rotational velocity of the halo with K-giant stars in LAMOST-Gaia era

LAMOST has obtained a large number of spectra for K-giant stars whose metallicities are well measured and released in DR5. Combining with the distances, radial velocities and proper motions provided by Gaia DR2, the full position and velocity information has been obtained. Using the Bayesian method we have constrained the rotational velocity of the halo and thick disk components in the local volume within 4 kpc from the Sun. The values of the rotational velocity are ? and ? for the halo and disk respectively, with the velocity of LSR assumed to be 232 km s^-1. The dispersions of the rotational velocity are ? and ? for the two components. What's more, another hot retrogradely rotating component is discovered.