2011ApJ...739L...9S

Hypercompact (HC) H II regions are, by nature, very young H II regions, associated with the earliest stages of massive star formation. They may represent the transition phase as an early B-type star grows into an O-type star. Unfortunately, so few HC H II regions are presently known that their general attributes and defining characteristics are based on small number statistics. A larger sample is needed for detailed studies and good statistics. Class II methanol masers are one of the best indicators of the early stages of massive star formation. Using the Arecibo Methanol Maser Galactic Plane Survey–the most sensitive blind survey for 6.7 GHz methanol masers to date–we selected 24 HC H II region candidates. We made Expanded Very Large Array continuum observations at 3.6 and 1.3 cm to search for HC H II regions associated with these masers. We identified six potential HC H II regions in our sample based on the presence of optically thick free-free emission. Overall, we find that 30% of the methanol masers have an associated centimeter radio continuum source (separation less than 0.1 pc), which is in general agreement with previous studies.