3D Kinematics of Classical Cepheids According to Gaia EDR3 Catalog

Abstract

The kinematics of about 2000 classical Cepheids of the Milky Way with data from Gaia EDR3 catalog has been studied. For some of these stars, there are line-of-sight velocities. On the basis of the nonlinear rotation model, the parameters of the rotation curve of the Galaxy were determined. The circular linear rotation velocity of the near-solar neighborhood around the Galaxy center was V 0 = 236 ± 3 km s−1 for the assumed Sun’s galactocentric distance R 0 = 8.1 ± 0.1 kpc. Analysis of residual velocities of Cepheids based on the linear Ogorodnikov–Milne model showed the presence of the following significantly different from zero gradients: ∂U/∂x, ∂U/∂z, ∂V/∂x, ∂V/∂z and ∂W/∂x, which behave differently depending on the selection radius. The most interesting is the gradient ∂W/∂x ∼ − 0.5 ± 0.1 km s−1 kpc−1 (positive rotation of this star system around the Galactic axis y, Ω y ) since the velocities W are free of Galactic rotation. Here we have an indirect influence of various effects leading to a perturbation of the vertical velocities of the Galactic disk stars. Based on a simpler model, a more accurate estimate of this rotation is obtained, Ω y = 0.51 ± 0.07 km s−1 kpc−1.