The Morphology of M17-uc1 – a Hyper-compact H Ii Region Surrounded by a Disk
نویسندگان
چکیده
Massive protostars evolve from hot cores to ultra-compact H II regions and eventually form classical H II regions; however, details of this evolution are far from understood. A few years ago, a new class of exceptionally small and dense objects, so-called hyper-compact H II regions, was discovered. They are believed to represent a transitional stage in early massive stellar evolution. Thus, their understanding is crucial for the formation of massive stars. In the present study, we investigate the morphology and the evolutionary stage of one of these hypercompact H II regions, M17-UC1. We investigated the source at infrared and radio wavelengths. M17-UC1 could be resolved into two emission areas separated by a dark lane reminiscent of a circumstellar disk. All observational evidence as well as model calculations suggest that M17-UC1 is surrounded by a disk of cold dust. This first detection of a circumstellar disk around a young hyper-compact H II region is in agreement with the expectations of the disk accretion model for massive star formation. Subject headings: stars: formation, circumstellar matter, pre-main sequence – open clusters and associations: general, individual (M17)
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