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 $d\lt 0.6\, \rm kpc$ and $|z|\lt 0.1\, \rm kpc$, selected from the LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) surveys. The radial and tangential velocities of these A-type stars are fitted by using a non-axisymmetric model. The best-fitting result yields the solar peculiar velocities $(U_\odot ,V_\odot ,W_\odot)=(11.69\pm 0.68, 10.16\pm 0.51, 7.67\pm 0.10)\, \rm km\, s^{-1}$ and Oort constants $A=16.31\pm 0.89\, \rm km\, s^{-1}\, kpc^{-1}$, $B=-11.99\pm 0.79\, \rm km\, s^{-1}\, kpc^{-1}$, $C=-3.10\pm 0.48\, \rm km\, s^{-1}\, kpc^{-1}$, and $K=-1.25\pm 1.04\, \rm km\, s^{-1}\, kpc^{-1}$. $|K+C|\gt 4\, \rm km\, s^{-1}\, kpc^{-1}$ means that there is a radial velocity gradient in the extended local disc, implying that the local disc is in a non-asymmetric potential. Using the derived Oort constants, we derive the local angular velocity $\Omega \, {\approx }\, A-B=28.30\pm 1.19\, \rm km\, s^{-1}\, kpc^{-1}$. By using A-type star sample of different volumes, we further try to evaluate the impacts of the ridge pattern in the R-Vϕ plane on constraining the solar motions and Oort constants. As the volume becomes larger towards the anticentre direction, the values of A and B become larger (implying a steeper slope of the local rotation curve) and the value of V⊙ becomes smaller probably caused by the ridge structure and its signal increasing with distance.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2021
- DOI:
- 10.1093/mnras/stab848
- arXiv:
- arXiv:2103.10232
- Bibcode:
- 2021MNRAS.504..199W
- Keywords:
-
- Galaxy: fundamental parameters;
- Galaxy: kinematics and dynamics;
- solar neighbourhood;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 10 pages, 10 figures, accepted for publication in MNRAS