Trigonometric Parallaxes of Massive Star Forming Regions: I. S 252 & G232.6+1.0

TL;DR

This study measures precise distances and motions of star-forming regions in the Milky Way using VLBA, revealing their locations and dynamics within Galactic spiral arms.

Contribution

First VLBA parallax measurements for S 252 and G232.6+1.0, refining their distances and Galactic positions, and providing insights into their motions within the Milky Way.

Findings

S 252 is in the Perseus arm at 2.10 kpc.

G232.6+1.0 is between the Carina-Sagittarius and Perseus arms at 1.68 kpc.

Both sources orbit slower than circular Galactic rotation.

Abstract

We are conducting a large program with the NRAO Very Long Baseline Array (VLBA) to measure trigonometric parallaxes of massive star-forming regions across the Milky Way. Here we report measurement of the parallax and proper motion of methanol masers in S 252 and G232.6+1.0. The parallax of S 252 is 0.476 +/- 0.006 mas (2.10 [+0.027/-0.026] kpc), placing it in the Perseus spiral arm. The parallax of G232.6+1.0 is 0.596 +/- 0.035 mas (1.68 [+0.11/-0.09] kpc), placing it between the Carina-Sagittarius and Perseus arms, possibly in a Local (Orion) spur of the Carina-Sagittarius arm. For both sources, kinematic distances are significantly greater than their parallax distances. Our parallaxes and proper motions yield full space motions accurate to about 1 km/s. Both sources orbit the Galaxy about 13 km/s slower than circular rotation.