Study of the Galactic Rotation Based on Masers and Radio Stars with VLBI Measurements of Their Parallaxes

TL;DR

This study uses VLBI measurements of parallaxes and proper motions of 256 radio sources, including masers and young stars, to refine Galactic rotation parameters, estimate the Sun's distance to the Galactic center, and analyze spiral density wave characteristics.

Contribution

It provides the most comprehensive sample to date for Galactic kinematic analysis, leading to new estimates of the Galactic center distance and detailed spiral density wave parameters.

Findings

Estimated the Sun's distance to the Galactic center as 8.15 kpc.

Determined amplitudes of radial and tangential velocity perturbations.

Derived wavelengths and phase angles of the Galactic spiral density wave.

Abstract

Based on published data, we have produced a sample of 256 radio sources whose trigonometric parallaxes and proper motions were measured by VLBI. This sample contains Galactic masers associated with massive protostars and stars in active star-forming regions. It also includes young low-mass stars from the Gould Belt region whose radio observations were performed in continuum. Based on this, most complete sample of sources to date, we have estimated the velocities $(U,V,W)_\odot$ and the parameters of the angular velocity of Galactic rotation $\Omega_0, \Omega^{(1)}_0, ... , \Omega^{(4)}_0$ and obtained a new estimate of the distance fromthe Sun to the Galactic center, $R_0=8.15^{+0.04}_{-0.20}$ kpc. The parameters of the Galactic spiral density wave have been found from the series of radial, $V_R$, and residual tangential, $\Delta V_{circ}$, velocities of stars. The amplitudes of the radial and tangential velocity perturbations are $f_R=7.0\pm0.9$ km s$^{-1}$ and $f_\theta=3.8\pm1.1$ km s$^{-1}$, the perturbation wavelengths are $\lambda_R=2.3\pm0.2$ kpc and $\lambda_\theta=2.0\pm0.4$ kpc, and the Sun's phases in the spiral density wave are $(\chi_\odot)_R=-163^\circ\pm9^\circ$ and $(\chi_\odot)_\theta=-137^\circ\pm10^\circ$ for the adopted four-armed spiral pattern.