SEARCH FOR OPTICALLY THICK H-II REGIONS AND IONIZED STELLAR WIND FROMLUMINOUS EMBEDDED INFRARED SOURCES

High-resolution radio continuum observations of 14 protostellar candid ates have been obtained using the VLA at 2 cm. The sources were chosen from a compilation of Wynn-Williams. Positive detections were made fo r W33A, OMC-2 IRS 4, S255 IRS 1, S255N, and NGC 6334V IRS 4, while 3 s igma upper limits of 0.15-0.5 mJy were obtained for 11 other sources. Additional 3.6 cm and 2 cm data were also obtained for W33A and OMC-2. In OMC-2 IRS 4, the radio source coincides with the northern source I RS 4N seen in the near-IR. The 3.6 cm emission of this source shows a faint extension in the same direction as the outflow inferred from inf rared polarization measurements. The total spectral energy distributio n of W33A at radio wavelengths is nearly flat and is consistent with a confined stellar wind model. In NGC 6334V IRS 4, a compact source sli ghtly displaced from the central 20 mu m source and extended emission corresponding to the eastern lobe of the bipolar flow observed in the near-IR are seen. The bolometric luminosity inferred from the radio co ntinuum emission assuming optically thin conditions is substantially l ess than the far-IR luminosity for most of the sources. For deeply emb edded high-luminosity young stars, this suggests that either the radio continuum emission is optically thick or the stellar source is still in the pre-main-sequence stage with low ionizing radiation.