Galactic Kinematics from Data on Open Star Clusters from the MWSC Catalogue

TL;DR

This study uses data from over 2000 open star clusters in the MWSC catalogue to determine Galactic rotation parameters and detect spiral density wave influences, providing updated measurements of the Milky Way's kinematics.

Contribution

The paper presents new estimates of Galactic rotation parameters and identifies spiral density wave effects using a large sample of open star clusters, including young clusters affected by spiral arms.

Findings

Galactic rotation velocity V_0=236±6 km/s at R_0=8.3±0.2 kpc.

Detection of spiral density wave influence in clusters younger than 50 Myr.

Measured perturbation amplitudes and wavelengths for the spiral arms.

Abstract

Open star clusters from the MWSC (Milky Way Star Clusters) catalogue have been used to determine the Galactic rotation parameters. The circular rotation velocity of the solar neighborhood around the Galactic center has been found from data on more than 2000 clusters of various ages to be V_0=236+/-6 km s^{-1} for the adopted Galactocentric distance of the Sun R_0=8.3+/-0.2 kpc. The derived angular velocity parameters are \Omega_0=28.48+/-0.36 km s^{-1} kpc^{-1}, \Omega'_0=-3.50+/-0.08 km s^{-1} kpc^{-2}, and \Omega"_0= 0.331+/-0.037 km s^{-1} kpc^{-3}. The influence of the spiral density wave has been detected only in the sample of clusters younger than 50 Myr. For these clusters the amplitudes of the tangential and radial velocity perturbations are f_\theta=5.6+/-1.6 km s^{-1} and f_R=7.7+/-1.4 km s^{-1}, respectively; the perturbation wavelengths are \lambda_\theta=2.6+/-0.5 kpc (i_\theta=-11+/-2 degrees) and \lambda_R=2.1+/-0.5 kpc (i_R=-9+/-2 degrees) for the adopted four-armed model (m=4). The Sun's phase in the spiral density wave is (\chi_\odot)_\theta=-62+/-9 degrees and (\chi_\odot)_R =-85+/-10 degrees from the residual tangential and radial velocities, respectively.