High-Resolution Centimeter Radio Continuum and Ammonia Maser Observations of the W51 Region of Star Formation

Abstract

view Abstract Citations (72) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-Resolution Centimeter Radio Continuum and Ammonia Maser Observations of the W51 Region of Star Formation Gaume, R. A. ; Johnston, K. J. ; Wilson, T. L. Abstract High angular resolution and high-sensitivity observations at wavelengths of 1.3 and 3.6 cm have detected three new ultracompact emission regions in the core of the W51 (regions d and e). In total, five ultracompact continuum objects of diameter less than 300 to 3000 AU are located in W51 d and e. These sources may best be explained as photoionized stellar winds. This suggests that there may exist a quasi-stable point in early stellar evolution where observable H II regions are formed by stellar winds around massive stars. These observations demonstrate that the taxonomy of H II region classification may be heavily affected by sensitivity, and a lack of complete spatial sampling by interferometric mapping. For example, the W51 d region, previously classified as cometary, is shown by our higher resolution and sensitivity observations also to have the properties normally associated with shell-like regions. These new observations suggest that the bow shock model, which is suggested to explain the morphology of cometary H II regions, but cannot explain shell sources, does not fully explain the W51 d H II region. The J, K = (9, 8) NH3 maser associated with W51 d has been shown to have a minimum brightness temperature of 2.7 × 106 K. This maser is most probably saturated. Publication: The Astrophysical Journal Pub Date: November 1993 DOI: 10.1086/173342 Bibcode: 1993ApJ...417..645G Keywords: ISM: H II REGIONS; ISM: INDIVIDUAL ALPHANUMERIC: W51; ISM: MOLECULES; ISM: STRUCTURE; MASERS; RADIO CONTINUUM: INTERSTELLAR full text sources ADS | data products SIMBAD (12)