The parallax of W43: A massive star-forming complex near the galactic bar

Abstract

We report trigonometric parallax measurements of masers in the massive star-forming complex W43 from Very Long Baseline Array observations as part of the Bar and Spiral Structure Legacy Survey. Based on measurements of three 12 GHz methanol maser sources (G029.86-00.04, G029.95-00.01, and G031.28+00.06) and one 22 GHz water maser source (G031.58+00.07) toward W43, we derived a distance of 5.49+0.39-0.34 kpc to W43. By associating the masers with CO molecular clouds, and associating the clouds kinematically with CO longitude-velocity spiral features, we assign W43 to the Scutum spiral arm, close to the near end of the Galactic bar. The peculiar motion of W43 is about 20 km s-1 toward the Galactic Center and is very likely induced by the gravitational attraction of the bar. © 2014. The American Astronomical Society. All rights reserved.