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 5,627 A-type stars with $d<0.6\, \rm kpc$ and $|z|<0.1\, \rm kpc$, selected from the LAMOST 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 $A=16.31\pm 0.89\, \rm km\, s^{-1}\, kpc^{-1}$, $B=-11.99\pm 0.79\, \rm km\, s^{-1}\, kpc^{-1}$, $C=-3.10\pm 0.48\, \rm km\, s^{-1}\, kpc^{-1}$, $K=-1.25\pm 1.04\, \rm km\, s^{-1}\, kpc^{-1}$, respectively. $|K+C|>4\, \rm km\, s^{-1}\, kpc^{-1}$ means that there is a radial velocity gradient in the extended local disk, implying the local disk 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 R-Vφ plane on constraining the solar motions and Oort constants. As the volume becomes larger toward the anti-center 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.

The diffuse interstellar band around 8620 Å

“…We obtained a median central wavelength in the (Reid & Brunthaler 2004;Schönrich et al 2010). For an exhaustive summary of the measurements of the solar motion, we refer the reader to Wang et al (2021). We note that a difference of ∆U = 1 km s −1 causes an error of ∼0.03 Å in λ 0 , while the typical error of C obs in the fit is about 0.36 Å.…”

Spiral density-wave structure parameters in the solar neighbourhood derived from longitudinal velocities of Gaia EDR3 OB stars: 3D approach

“…(xi) Considering the m ≥ 1 models, our sample of OB stars yields the first and second Oorts constants A 0 ≈ +10 km s −1 kpc −1 , B 0 ≈ −19 km s −1 kpc −1 , whereas the conventional values are A conv ≈ +15 km s −1 kpc −1 , B conv ≈ −12 km s −1 kpc −1 (e.g. Bovy 2017;Wang et al 2021). Accordingly, the Galaxy rotates more like a solid body and the mass density depends more weekly on r (the local disc is more homogeneous) than in the conventional m = 0 model (cf.…”

“…(xii) The last point is that measurements of u 0 ≈ −6 km s −1 (radially towards the GC) and v 0 ≈ +10 km s −1 (in the direction of Galactic rotation) are not too far from the conventional values of ≈−10 km s −1 and ≈+15 km s −1 (Schönrich, Binney & Dehnen 2010;Reid & Brunthaler 2020;Gaia Collaboration 2021;Wang et al 2021).…”

Kinematics of the molecular interstellar medium probed by Gaia: steep velocity dispersion-size relation, isotropic turbulence, and location-dependent energy dissipation

“…We also plotted the expected velocity dispersion assuming that the clouds contain no turbulence such that all velocities we observe come from shear by assuming a Oort constant of 𝐴 = 16.31 ± 0.89 km s −1 kpc −1 from Wang et al (2021) in Fig. 7.…”