Kinematics of the Galaxy from OB Stars with Data from the Gaia DR2 Catalogue

Abstract

We have selected and analyzed a sample of OB stars with known line-of-sight velocities determined through ground-based observations and with trigonometric parallaxes and proper motions from the Gaia DR2 catalogue. Some of the stars in our sample have distance estimates made from calcium lines. A direct comparison with the trigonometric distance scale has shown that the calcium distance scale should be reduced by 13\%. The following parameters of the Galactic rotation curve have been determined from 495 OB stars with relative parallax errors less than 30\%: $(U,V,W{)}_{\odot }=(8.16,11.19,8.55)\pm (0.48,0.56,0.48)$ km s${}^{-1}$, ${\Omega }_0=28.92\pm 0.39$ km s${}^{-1}$ kpc${}^{-1}$, ${\Omega }_0^{{}^{\prime }}=-4.087\pm 0.083$ km s${}^{-1}$ kpc${}^{-2}$ and ${\Omega }_0^{{}^{\prime \prime }}=0.703\pm 0.067$ km s${}^{-1}$ kpc${}^{-3}$, where the circular velocity of the local standard of rest is $V_0=231\pm 5$ km s${}^{-1}$ (for the adopted $R_0=8.0\pm 0.15$ kpc). The parameters of the Galactic spiral density wave have been found from the series of radial, $V_R,$ residual tangential, $\Delta V_{circ}$, and vertical, $W,$ velocities of OB stars by applying a periodogram analysis. The amplitudes of the radial, tangential, and vertical velocity perturbations are $f_R=7.1\pm 0.3$ km s${}^{-1}$, $f_{\theta }=6.5\pm 0.4$ km s${}^{-1}$, and $f_W=4.8\pm 0.8$ km s${}^{-1}$, respectively; the perturbation wavelengths are ${\lambda }_R=3.3\pm 0.1$ kpc, ${\lambda }_{\theta }=2.3\pm 0.2$ kpc, and ${\lambda }_W=2.6\pm 0.5$ kpc; and the Sun's radial phase in the spiral density wave is $({\chi }_{\odot }{)}_R=-135\pm 5^{\circ }$, $({\chi }_{\odot }{)}_{\theta }=-123\pm 8^{\circ }$, and $({\chi }_{\odot }{)}_W=-132\pm 21^{\circ }$ for the adopted four-armed spiral pattern.

16 pages,6 figures, 1 table

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• Kinematics of OB Stars with Data from the LAMOST and Gaia Catalogues
• Analysis of Close Stellar Encounters with the Solar System
• Parameters of the Galactic Spiral Density Wave from Masers with Parallax Errors Less Than 10%
• Galaxy Rotation Parameters from OB2 Stars with Proper Motions and Parallaxes from the Gaia EDR3 Catalog
• Kinematic Properties of Young Intermediate- and Low-Mass Stars from the Gaia DR2 Catalogue
• Estimation of Galactic Spiral Density Wave Parameters Based on the Velocities of OB2 stars from the Gaia EDR3 Catalogue