On the Accuracy of Three-dimensional Kinematic Distances

TL;DR

This paper evaluates the accuracy of 3D kinematic distances for mapping the Milky Way, finding they are more reliable than parallaxes for sources beyond the Galactic center, aiding galactic structure studies.

Contribution

It demonstrates that 3D kinematic distances provide a robust alternative to parallaxes for distant Galactic sources, especially past the Galactic center.

Findings

3D kinematic distances are more accurate than parallaxes beyond the Galactic center.

Systematic uncertainties affect kinematic distances within 10 kpc of the Sun.

Parallaxes remain superior for nearby sources within 10 kpc.

Abstract

Over the past decade, the BeSSeL Survey and the VERA project have measured trigonometric parallaxes to approximately 250 massive, young stars using VLBI techniques. These sources trace spiral arms over nearly half of the Milky Way. What is now needed are accurate distances to such stars which are well past the Galactic center. Here we analyze the potential for addressing this need by combining line-of-sight velocities and proper motions to yield 3D kinematic distance estimates. For sources within about 10 kpc of the Sun, significant systematic uncertainties can occur, and trigonometric parallaxes are generally superior. However, for sources well past the Galactic center, 3D kinematic distances are robust and more accurate than can usually be achieved by trigonometic parallaxes.