Local stellar kinematics and Oort constants from the LAMOST A-type stars

ABSTRACT We estimate the solar peculiar velocities and Oort constants using a sample of 5627 A-type stars with $d\lt 0.6\, \rm kpc$ $|z|\lt 0.1\, kpc$, selected from LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) surveys. The radial tangential these are fitted by non-axisymmetric model. best-fitting result yields $(U_\odot ,V_\odot ,W_\odot)=(11.69\pm 0.68, 10.16\pm 0.51, 7.67\pm 0.10)\, km\, s^{-1}$ $A=16.31\pm 0.89\, s^{-1}\, kpc^{-1}$, $B=-11.99\pm 0.79\, $C=-3.10\pm 0.48\, $K=-1.25\pm 1.04\, kpc^{-1}$. $|K+C|\gt 4\, kpc^{-1}$ means that there is velocity gradient in extended local disc, implying disc non-asymmetric potential. Using derived constants, we derive angular $\Omega \, {\approx }\, A-B=28.30\pm 1.19\, By star different volumes, further try to evaluate impacts ridge pattern R–Vϕ plane on constraining motions constants. As volume becomes larger towards anticentre direction, values A B become (implying steeper slope rotation curve) value V⊙ smaller probably caused structure its signal increasing distance.