0000000000544652
AUTHOR
K. Hachisuka
The kinematics of water masers in the stellar molecular outflow source, IRAS 19134+2131
Using the Very Large Array (VLA) and the Very Long Baseline Array (VLBA), we have observed water maser emission in the proto-planetary nebula candidate IRAS 19134+2131, in which the water maser spectrum has two groups of emission features separated in radial velocity by ∼100 km s^−1. The blue-shifted and red-shifted clusters of maser features are clearly separated spatially by ∼150 mas, indicative of a fast collimated flow. However, not all of the maser features are aligned along the axis of the flow, as is seen in the similar high-velocity water maser source, W43A. Comparing the VLA and VLBA maps of the water maser source, we find 4 maser features that were active for 2 years. Using only V…
Water Maser Motions in W3(OH) and a Determination of Its Distance
We report phase-referencing VLBA observations of H2O masers near the star-forming region W3(OH) to measure their parallax and absolute proper motions. The measured annual parallax is 0.489 +/- 0.017 milli-arcseconds (2.04 +/- 0.07 kpc), where the error is dominated by a systematic atmospheric contribution. This distance is consistent with photometric distances from previous observations and with the distance determined from CH3OH maser astrometry presented in a related paper. We also find that the source driving the H2O outflow, the ``TW-object'', moves with a 3-dimensional velocity of > 7 km/s relative to the ultracompact HII region W3(OH).
Towards an Understanding of the Dynamics of the Milky Way
Determination of outer rotation curve using Galactic masers The rotation curve of the Galaxy is poorly determined outside the solar circle (e.g. Honma & Sofue 1997). The situation makes difficult to derive the dynamical mass of the Galaxy, which is essential for inferring the amount of Galactic dark gravitating matter. We selected Galactic masers in this study since they distributed over the whole Galaxy. Moreover, they can observed with VLBI at extremely high angular resolution, allowing a measurement of the annual parallax, and thus the source’s distance, and its proper motion due to Galactic rotation with phase referencing VLBI astrometric observation. We have already performed phase-ref…