Water Masers Toward Ultracompact H ii Regions

We present a survey in the 6 16 –5 23 rotational H 2 O transition toward 33 Galactic ultracompact H II regions. Maser emission is detected toward 18 of these sources; two are new detections. High-quality spectra are provided for all 18 sources. We discuss the detection rate of this survey and the correlation of various maser properties with other physical parameters. In addition, we report wide-bandwidth (316 km s -1 ), moderate-resolution (∼3'') H 2 O maser observations of the HH 80–81 region. We report the first detection of water maser emission at the approximate velocity of the molecular core. This emission is coincident with the extreme tip of the thermal jet and well removed from the much stronger and well-known maser emission at the position of VLA 3.