Trigonometric Parallaxes of Four Star-forming Regions in the Distant Inner Galaxy

TL;DR

This study measures precise distances to four star-forming regions in the inner Galaxy using VLBA parallax observations, revealing their locations relative to Galactic structures like the bar and spiral arms.

Contribution

It provides new trigonometric parallax measurements for four distant star-forming regions, improving understanding of their positions within the Galaxy's structure.

Findings

G026.50+0.28 is at the near end of the Galactic bar.

G020.77-0.05 is in the Galactic Center region.

G019.60-0.23 and G020.08-0.13 are likely in the Sagittarius arm.

Abstract

We have measured trigonometric parallaxes for four water masers associated with distant massive young stars in the inner regions of the Galaxy using the VLBA as part of the BeSSeL Survey. G026.50$+$0.28. is located at the near end of the Galactic bar, perhaps at the origin of the Norma spiral arm. G020.77$-$0.05 is in the Galactic Center region and is likely associated with a far-side extension of the Scutum arm. G019.60$-$0.23 and G020.08$-$0.13 are likely associated and lie well past the Galactic Center. These sources appear to be in the Sagittarius spiral arm, but an association with the Perseus arm cannot be ruled out.