Parameters of the Galactic Spiral Density Wave from Masers with Parallax Errors Less Than 10%

TL;DR

This study analyzes VLBI-measured masers to determine Galactic rotation and spiral density wave parameters, revealing the wave's influence on vertical velocities and confirming the Radcliffe wave in the Local Arm.

Contribution

It provides new estimates of the Galactic rotation velocity and spiral density wave parameters using masers with high-precision parallaxes, including vertical velocity analysis.

Findings

Galactic rotation velocity at R0 is 244.4 km/s.

Spiral density wave wavelength is approximately 2.1 kpc.

Vertical velocities show influence of spiral density wave.

Abstract

We have studied the kinematics of Galactic masers and radio stars with measured VLBI trigonometric parallaxes and proper motions. We have considered masers with relative trigonometric parallax errors less than 10\% and determined the Galactic rotation parameters from them. In particular, the linear rotation velocity of the Galaxy at the solar distance $R_0$ has been found to be $244.4\pm4.3$ km s$^{-1}$ (for the adopted $R_0=8.1\pm0.1$ kpc). We have performed a joint and separate spectral analysis of the radial, residual tangential, and vertical maser velocities. For example, from the vertical maser velocities we have estimated the velocity perturbation amplitude $f_W=5.2\pm1.5$ km s$^{-1}$ with the wavelength $\lambda_W=2.6\pm0.7$ kpc, arguing for the influence of the spiral density wave on the vertical stellar velocities. Based on 104 masers within 3 kpc of the Sun, as a result of the joint solution, we have estimated the radial, $f_R=6.7\pm1.1$ km s$^{-1}$, and tangential, $f_\theta=2.6\pm1.2$ km s$^{-1}$, velocity perturbations, the perturbation wavelength $\lambda=2.1\pm0.3$ kpc, and the Sun's phase in the Galactic spiral density wave $\chi_\odot=-148\pm15^\circ$. We have confirmed the presence of the Radcliffe wave in the spatial distribution of masers and radio stars belonging to the Local Arm.