The Spiral Structure and Kinematics of the Milky Way

We are conducting a VLBA Key Project (BR145) to study the spiral structure and kinematics of the Milky Way. We will accomplish this by determining distances, via trigonometric parallax, and proper motions of star forming regions in the Milky Way. The target sources are methanol and water masers that are associated with young massive stars and compact HII regions that trace spiral structure. With accurate distance measurements we will locate spiral arms, and with absolute proper motions we can determine the 3-dimensional motions of these massive young stars.

Over the past decade, we have developed and tested the techniques needed to achieve better than 0.03 mas relative positional accuracy between maser sources and background QSOs at each epoch. Before beginning this project, we completed program BR100 from which we determined trigonometric parallaxes to 11 star forming regions with accuracies of order 0.01 mas. We also measured absolute proper motions with accuracies of order 1 km/s. These results have been published in a series of papers in the Astrophyscial Journal in 2009.

Project Team

Mark Reid & Tom Dame: Harvard-Smithsonian Center for Astrophysics, USA

Karl Menten, Andreas Brunthaler & Yoon Kyung Choi: Max-Planck-Institut fuer Radioastronomie, Germany

Xu Ye: Purple Mountain Observatory, China

Zheng Xing-Wu & Zhang Bo: Nanjing University, China

Luca Moscadelli & Alberto Sanna: Arcetri Observatory, Italy

George Moellenbrock, NRAO, USA

Mayumi Sato, Tokyo University, Japan

Anna Bartkiewicz: Torun Observatory, Poland

Kazuya Hachisuka: Shanghai Observatory, China

Project Information

  • Proposal
  • Pre-parallax Observations

  • Preparatory Surveys
  • Parallax Observations