Kinematics of the Galaxy from a Sample of Young Open Star Clusters with Data from the Gaia DR2 Catalogue

Abstract

We have selected a sample of 326 young (log t < 8) open star clusters with the proper motions and distances calculated by various authors from Gaia DR2 data. The mean values of their line-of-sight velocities have also been taken from various publications. As a result of our kinematic analysis, we have found the following parameters of the angular velocity of Galactic rotation: Ω₀ = 29.34 ± 0.31 km s^-1 kpc^-1, Ω'₀ = -4.012 ± 0.074 kms^-1 kpc^-2, and Ω″₀ = 0.779 ± 0.062 kms^-1 kpc^-3. The circular rotation velocity of the solar neighborhood around the Galactic center is V ₀ = 235 ± 5 km s^-1 for the adopted Galactocentric distance of the Sun R ₀ = 8.0 ± 0.15 kpc. The amplitudes of the tangential and radial velocity perturbations produced by the spiral density wave are f _θ = 3.8 ± 1.2 km s^-1 and f _R = 4.7 ± 1.0 km s^-1, respectively; the perturbation wavelengths are λ _θ = 2.3 ± 0.5 kpc and λ _r = 2.2 ± 0.5 kpc for the adopted four-armed spiral pattern. The Sun's phase in the spiral density wave is close to χ _⊙ = -120° ± 10°.