Water Masers in W49 North and Sagittarius B2
Abstract
Using the Very Large Array (VLA) of the National Radio Astronomy Observatory in the A and B configurations, we have obtained simultaneous high resolution observations of both the 22 GHz water maser lines as well as the 22 GHz continuum for the H II regions W49N and Sagittarius B2. The angular resolution of both observations is ~0.1", which at the distance of W49N (11.4 kpc; Gwinn, Moran, & Reid 1992) and Sgr B2 (8.5 kpc) corresponds to a physical size of <1000 AU in both sources. The velocity coverage for W49N is +/- 435 km/s; positions for 316 water maser components were obtained. The velocity coverage for Sgr B2 is -40 to +120 km/s; positions for 68 maser components were determined in Sgr B2 Main, 79 in Sgr B2 North, 14 in Sgr B2 Mid-North, and 17 in Sgr B2 South, for a total of 178 water maser positions in Sgr B2. The cross calibration scheme of Reid & Menten (1990, 1997) was used. Using this procedure, high dynamic range continuum images were obtained with accurate registration (rms ~0.01") of the continuum and maser positions. A detailed comparison between H II components and maser positions for both Sgr B2 and W49N is presented. In Sgr B2 Main, the water masers are predominantly located at the outside edge of the high-frequency continuum, lending support to the proposal that entrainment by stellar winds may play an important role in water maser emission.
Cite
@article{arxiv.astro-ph/0407410,
title = {Water Masers in W49 North and Sagittarius B2},
author = {E. J. McGrath and W. M. Goss and C. G. De Pree},
journal= {arXiv preprint arXiv:astro-ph/0407410},
year = {2008}
}
Comments
37 pages, including 6 figures and 6 tables. Accepted for publication in ApJS (Nov. 2004, v155). Data tables 2 - 6 are available in electronic format along with full resolution figures upon request ([email protected])