1999ApJ...516..817K

To investigate their dust properties, we have imaged three sites of massive star formation in the giant H II region/star-forming cloud NGC 6334 with the MIRAC2 instrument. We obtained high-resolution (1") continuum images at 12.5 and 20.6 µm toward each region, which were compared with observations of the radio and near-infrared (near-IR) continuum emission. Both compact sources and extended emission were found at all three star-forming sites. The detected sources span a wide range of evolutionary states in this highly complex star-forming cloud. The infrared sources near NGC 6334 I were resolved into at least four subsources. One such source is substantially colder, denser, and more optically thick than the other mid-IR sources in the region and may be at the earliest stages of stellar formation. Another may be a torus or disk of dust and gas surrounding an embedded B star. NGC 6334 I was also imaged at additional wavelengths (8.8, 9.8, and 11.7 µm) to search for silicate absorption. Only at the H II region is there a deep silicate absorption feature from foreground dust. Toward the NGC 6334 IV, warm dust is associated with both the inner portions of the massive molecular torus or disk and with the bipolar continuum lobes. A compact mid-IR source, associated with the near-IR and radio source [HHS87] IRS 20, is cooler and more optically thick than the dust emission associated with the H II region. Toward NGC 6334 V, four embedded sources were found, including one previously unidentified object. This newly identified compact object, associated with a dust temperature peak and a radio source, is probably in a more advanced stage of star formation than the other compact mid-IR sources in NGC 6334.