Maser astrometry with VERA and Galactic structure

Abstract

Abstract. Since 2007 VERA (VLBI Exploration of Radio Astrometry) has been producing astrometric results (distances and/or proper motions) for Galactic maser sources. Nearly 30 parallaxes have been obtained for star-forming regions and late-type stars. By using VERA's astrometric results for star-forming regions, combined with those obtained with VLBA and EVN, fundamental Galactic parameters and Galactic structure may be derived. Our results show that R 0 = 8.4 ± 0.4 kpc and Ω ≡ Ω0 + V /R0 = 30.7 ± 0.8 km s −1 kpc −1 , and also show that the rotation curve of the Galaxy is nearly flat. The determinations of Galactic parameters and structures demonstrate that the maser astrometry can not only contribute significantly to research of individual maser sources, but also to studies of the structure of the Galaxy.

SiO Maser Surveys of Nearby Miras and their Kinematics in the Galaxy

“…One example is the case of VY Canis Majoris observed by Choi et al (2008). With this telescope, the accurate parallax and proper motions have been obtained for about 20 miras, and more will come in the near future (Honma 2012). Though current progress is limited to the very bright objects only, they will reveal some spatial motions of SiO maser sources, and will give precise complete 3D spatial motions of these stars in the Galaxy, as well as the motion of the maser clouds in the spiral arms.…”