Trigonometric Parallaxes of Four Star-forming Regions in the Distant Inner Galaxy
Ye Xu, Shuaibo Bian, M. J. Reid, J. J. Li, K. M. Menten, T. M. Dame, Bo Zhang, A. Brunthaler, Yuanwei Wu, L. Moscadelli, Gang Wu, Xin Zheng
Abstract
Abstract We have measured trigonometric parallaxes for four H 2 O masers associated with distant massive young stars in the inner regions of the Galaxy using the Very Long Baseline Array 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.