G5.89-0.39 - A COMPACT H-II REGION WITH A VERY DENSE CIRCUMSTELLAR DUST TORUS

We present the results of high angular resolution infrared observation s of the compact H II region G5.89-0.39. Subarcsecond imaging at 1.65, 2.2, 3.6, and 4.8 mum and diffraction-limited scans at 50 and 100 mum have been obtained at NASA's Infrared Telescope Facility and Kuiper A irborne Observatory and the Canada-France-Hawaii Telescope. We find a bipolar source morphology at the shortest infrared wavelengths, a comp act single source at 4-5 mum, similar to that seen at 10 mum, and a ve ry high optical depth, barely resolved far-infrared source. Spherical radiative transfer models have been used to estimate dust envelope pro perties; in spite of the obvious nonspherical geometry at short wavele ngths, these models provide strong constraints on the overall properti es of the circumnebular envelope. We find that the bulk of the circums tellar dust must be relatively close to the H II region, with a relati vely steep density gradient. The high column densities and steep densi ty gradient imply densities at the inner edge of the cloud of order 10 (7)-10(8) cm-3. These results suggest that the compact H II region is surrounded by a very dense dust torus.