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; Hideyuki Kobayashi; Seisuke Kuji; Tomoharu Kurayama; Seiji Manabe; Takeshi Miyaji; Takumi Nagayama; Akiharu Nakagawa; Chung Sik Oh; Toshihiro Omodaka; Tomoaki Oyama; Satoshi Sakai; Katsuhisa Sato; Tetsuo Sasao; Katsunori M. Shibata; Motonobu Shintani; Hiroshi Suda; Yoshiaki Tamura; Miyuki Tsushima; Kazuyoshi Yamashita

doi:10.1093/pasj/59.5.889

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arXiv · 0709.0820

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

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Abstract

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 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 on the existence of large amount of dark matter in the Galaxy's outer disk.

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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, Hideyuki Kobayashi, Seisuke Kuji, Tomoharu Kurayama, Seiji Manabe, Takeshi Miyaji, Takumi Nagayama, Akiharu Nakagawa, Chung Sik Oh, Toshihiro Omodaka, Tomoaki Oyama, Satoshi Sakai, Katsuhisa Sato, Tetsuo Sasao, Katsunori M. Shibata, Motonobu Shintani, Hiroshi Suda, Yoshiaki Tamura, Miyuki Tsushima, Kazuyoshi Yamashita. 2007-09-06. Astrometry of Galactic Star Forming Region Sharpless 269 with VERA : Parallax Measurements and Constraint on Outer Rotation Curve. https://doi.org/10.1093/pasj%2F59.5.889

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