PREPRINT
C0C500F5-96ED-4566-855F-9BD7A218E68E

# Kinematics of OB Stars with Data from the LAMOST and Gaia Catalogues

V. V. Bobylev, A. T. Bajkova, G. M. Karelin
arXiv:2207.01924

Submitted on 5 July 2022

## Abstract

We have analyzed the kinematics of OB stars from the list by Xiang et al. (2021) that contains $\sim$13 000 single OB stars. For these stars there are photometric distance estimates and proper motions from the Gaia catalogue and line-of-sight velocities from the LAMOST catalogue. Based on a sample of single OB stars and using the photometric distances and proper motions of stars from the Gaia EDR3 catalogue, we have found the group velocity components $\left({U}_{\odot },{V}_{\odot },{W}_{\odot }\right)=\left(9.63,9.93,7.45\right)±\left(0.27,0.34,0.10\right)$ km s${}^{-1}$, and the following parameters of the angular velocity of Galactic rotation: ${\mathrm{\Omega }}_{0}=29.20±0.18$ km s${}^{-1}$ kpc${}^{-1}$, ${\mathrm{\Omega }}_{0}^{{}^{\prime }}=-4.150±0.046$ km s${}^{-1}$ kpc${}^{-2}$ and ${\mathrm{\Omega }}_{0}^{{}^{″}}=0.795±0.018$ km s${}^{-1}$ kpc${}^{-3}$, where the error per unit weight ${\sigma }_{0}$ is 9.56 km s${}^{-1}$ and ${V}_{0}=236.5±3.3$ km s${}^{-1}$ (for the adopted ${R}_{0}=8.1±0.1$ kpc). Based on the same OB stars, we have found the residual velocity dispersions $\left({\sigma }_{1},{\sigma }_{2},{\sigma }_{3}\right)=\left(15.13,9.69,7.98\right)±\left(0.07,0.05,0.04\right)$ km s${}^{-1}$. We show that using the line-of-sight velocities increases significantly the space velocity dispersion and leads to a biased estimate of the velocity ${U}_{\odot }$. A comparison of the distances scales used has shown that the photometric distances from Xiang et al. (2021) should be lengthened approximately by 10%.

## Preprint

Comment: 19 pages, 5 figures, 4 tables

Subject: Astrophysics - Astrophysics of Galaxies