Print Y. W. Wu , M. J. Reid, N. Sakai , T. M. Dame, K. M. Menten, A. Brunthaler, Y. Xu , J. J. Li , B. Ho, B. Zhang
Abstract: As part of the BeSSeL Survey, we report trigonometric parallaxes and proper motions of molecular maser sources associated with 13 distant high-mass star-forming regions in the Sagittarius spiral arm of the Milky Way. In particular, we obtain improved parallax distance estimates for three well-studied regions:
kpc for M17, 
kpc for W51, and 
kpc for GAL 045.5+00.0. Peculiar motions for all but one source are less than 20 km s1. We fit a log-periodic spiral to the locations and estimate an average pitch angle of 
. We find that the section of the arm beyond the tangent point in the first quadrant of the Milky Way appears 15 pc below the IAU-defined Galactic plane.