1. Multi-epoch VERA Observations of H2O masers in OH 43.8-0.1
- Author
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Honma, M., Bushimata, T., Choi, Y. K., Fujii, T., Hirota, T., Horiai, K., Imai, H., Inomata, N., Ishitsuka, J., Iwadate, K., Jike, T., Kameya, O., Kamohara, R., Kan-ya, Y., Kawaguchi, N., Kijima, M., Kobayashi, H., Kuji, S., Kurayama, T., Manabe, S., Miyaji, T., Nakagawa, A., Nakashima, K., Oh, C. S., Omodaka, T., Oyama, T., Rioja, M., Sakai, S., Sato, K., Sasao, T., Shibata, K. M., Shimizu, R., Sora, K., Suda, H., Tamura, Y., and Yamashita, K.
- Subjects
Astrophysics - Abstract
We report on the multi-epoch observations of H2O maser emission in star forming region OH 43.8-0.1 carried out with VLBI Exploration of Radio Astrometry (VERA). The large-scale maser distributions obtained by single-beam VLBI mapping reveal new maser spots scattered in area of 0.7 x 1.0 arcsec, in addition to a `shell-like' structure with a scale of 0.3 x 0.5 arcsec which was previously mapped by Downes et al.(1979). Proper motions are also obtained for 43 spots based on 5-epoch monitoring with a time span of 281 days. The distributions of proper motions show a systematic outflow in the north-south direction with an expansion velocity of ~8 km/s, and overall distributions of maser spots as well as proper motions are better represented by a bipolar flow plus a central maser cluster with a complex structure, rather than a shell with a uniform expansion such as those found in Cep A R5 and W75N VLA2. The distance to OH 43.8-0.1 is also estimated based on the statistical parallax, yielding D = 2.8 +/- 0.5 kpc. This distance is consistent with a near kinematic distance and rules out a far kinematics distance (~9 kpc), and the LSR velocity of OH 43.8-0.1 combined with the distance provides a constraint on the flatness of the galactic rotation curve, that there is no systematic difference in rotation speeds at the Sun and at the position of OH 43.8-0.1, which is located at the galacto-centric radius of ~6.3 kpc., Comment: 10 pages, 2 figures and 2 tables included, to appear in PASJ (vol. 57, #4, 2005, August)
- Published
- 2005