A Class of Interstellar OH Masers Associated with Protostellar Outflows

Using the Very Large Array, we have detected weak OH maser emission near the Turner-Welch protostellar source in the W3 OH region. Unlike typical interstellar OH masers, which are associated with ultracompact H II regions, our measured positions and proper motions (from very long baseline interferometry) indicate that these OH masers are associated with a bipolar outflow traced by strong H 2 O masers. These OH masers may be part of a class of interstellar OH masers that are associated with very young stars that have yet to, or may never, create ultracompact H II regions. This class of OH masers appears to form near the edges of very dense material (within which H 2 O masers form), where total densities drop precipitously and interstellar UV radiation is sufficient to dissociate the H 2 O molecules. Observations of this class of OH masers may be an important way to probe the distribution of this important molecule in interstellar shocks at arcsecond resolution or better.