Portal de Periódicos da CAPES

A C 17 O Survey toward Ultracompact H ii Regions

2000; IOP Publishing; Volume: 536; Issue: 1 Linguagem: Inglês

10.1086/308903

1538-4357

P. Höfner, F. Wyrowski, C. M. Walmsley, E. Churchwell,

Molecular Spectroscopy and Structure

We have observed 16 regions of massive star formation in the J = 1-0, 2-1 rotational transitions of C17O and the J = 2-1 transition of C18O with the IRAM 30 m telescope. We have also observed the J = 2-1, 3-2 rotational transitions of C17O with the KOSMA 3 m telescope. The C17O-emitting clumps typically have sizes of 1 pc and average densities and temperatures of 105 cm-3 and 25 K, respectively. Clump masses from 103 to 4 × 104 M☉ are found, and most of the clumps are virialized in the sense that their gravitational energy is of the same order as bulk kinetic energy inferred from the line width. We also compare the derived masses with values obtained using measurements of the millimeter/submillimeter dust continuum emission and find that the dust continuum masses tend to be higher by about a factor of 2. We estimate the masses of early-type stars (more massive than 15 M☉) embedded in the sources of our sample and conclude that the ratio of "O-star mass" to gas mass is roughly 1% in most cases.