The Spiral Structure and Kinematics of the Milky Way

We are conducting a large project (BR100) with the VLBA 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 12 GHz methanol masers which 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 0.05 mas relative positional accuracy between maser sources and a background QSO at each epoch. As a proof of technique, we have determined the trigonometric parallax to W3OH with an accuracy of 0.01 mas and also measured its absolute proper motion with an accuracy of 1 km/s. We are now conducting similar observations of a dozen methanol masers, sampling the Perseus, Sagittarius, Scutum and Norma spiral arms in the first and second quadrants of the Milky Way.

Project Team

Mark Reid & Lincoln Greenhill: Harvard-Smithsonian Center for Astrophysics

Karl Menten: Max-Planck-Institut fuer Radioastronomie

Ye Xu: Max-Planck-Institut fuer Radioastronomie & Shanghai Astronomical Observatory

Xing Wu Zheng: Nanjing University

Luca Moscadelli: Obs. Astron. Cagliari

Project Overview

  • Background Information

  • Project Goals

  • Demonstration Observations: W3OH

  • Observational Strategy

    • Observation Schedule

  • Observation Plan