3-D kinematics of classical Cepheids according to Gaia, EDR3 catalog

TL;DR

This study analyzes the 3-D kinematics of about 2000 Milky Way classical Cepheids using Gaia EDR3 data, determining the Galaxy's rotation curve and revealing significant velocity gradients and vertical perturbations.

Contribution

It provides new measurements of the Galactic rotation curve and identifies velocity gradients and vertical perturbations using Gaia EDR3 Cepheid data.

Findings

Circular velocity near the Sun is 236 km/s.

Detected significant velocity gradients in Cepheid residual velocities.

Estimated the vertical rotation component as approximately 0.51 km/s/kpc.

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 $V_0=236\pm 3$~km s$^{-1}$ for the assumed Sun's galactocentric distance $R_0=8.1\pm0.1$~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: $\partial U/\partial x,$ $\partial U/\partial z,$ $\partial V/\partial x,$ $\partial V/\partial z$ and $\partial W/\partial x,$ which behaves differently depending on the selection radius. The most interesting is the gradient $\partial W/\partial x\sim-0.5\pm0.1$~km s$^{-1}$ kpc$^{-1}$ (positive rotation of this star system around the galactic axis $y$, $\Omega_y$) 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, $\Omega_y=0.51\pm0.07$~km s$^{-1}$ kpc$^{-1}$.