Astrometry of galactic star-forming region sharpless 269 with VERA: Parallax measurements and constraint on outer rotation curve

作者：Honma Mareki^*; Bushimata Takeshi; Choi Yoon Kyung; Hirota Tomoya; Imai Hiroshi; Iwadate Kenzaburo; Jike Takaaki; Kameya Osamu; Kamohara Ryuichi; Kan Ya Yukitoshi; Kawaguchi Noriyuki; Kijima Masachika; Kobayashi Hideyuki; Kuji Seisuke; Kurayama Tomoharu; Manabe Seiji; Miyaji Takeshi; Nagayama Takumi; Nakagawa Akiharu; Oh Chung Sik; Omodaka Toshihiro; Oyama Tomoaki; Sakai Satoshi; Sato Katsuhisa; Sasao Tetsuo; Shibata Katsunori M; Shintani Motonobu; Suda Hiroshi

来源：Publications of the Astronomical Society of Japan, 2007, 59(5): 889-895.

• ISM : star forming regions
• ISM : individual (Sharpless 269)
• masers (H2O)
• VERA

We have performed high-precision astrometry of H2O maser sources in the Galactic star-forming region Sharpless 269 (S269) with VERA. We successfully detected a trigonometric parallax of 189 8 mu as, corresponding to a source distance of 5.2 8(-0.22)(+0.24) kpc. This is the smallest parallax ever measured, and the first one detected beyond 5 kpc. The source distance as well as the proper motions were used to constrain the outer rotation curve of the Galaxy, demonstrating that the difference of 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 of the existence of a large amount of dark matter in the Galaxy's outer disk.

• 出版日期2007
• 单位中国科学院国家天文台