Astrometry of Galactic Star-Forming Region Sharpless 269 with VERA: Parallax Measurements and Constraint on Outer Rotation Curve

Mareki Honma, Takeshi Bushimata, Yoon Kyung Choi, Tomoya Hirota, Hiroshi Imai, Kenzaburo Iwadate, Takaaki Jike, Osamu Kameya, Ryuichi Kamohara, Yukitoshi Kan-ya, Noriyuki Kawaguchi, Masachika Kijima (+19 others)
2007 Nippon Tenmon Gakkai obun kenkyu hokoku  
We have performed high-precision astrometry of H2O maser sources in Galactic star forming region Sharpless 269 (S269) with VERA. We have successfully detected a trigonometric parallax of 189+/-8 micro-arcsec, corresponding to the source distance of 5.28 +0.24/-0.22 kpc. This is the smallest parallax ever measured, and the first one detected beyond 5 kpc. The source distance as well as proper motions are used to constrain the outer rotation curve of the Galaxy, demonstrating that the difference
more » ... f rotation velocities at the Sun and at S269 (which is 13.1 kpc away from the Galaxy's center) is less than 3%. This gives the strongest constraint on the flatness of the outer rotation curve and provides a direct confirmation on the existence of large amount of dark matter in the Galaxy's outer disk.
doi:10.1093/pasj/59.5.889 fatcat:up42tfvai5ckzonypx6aowgkje