Astronomy and Astrophysics – Astronomy
Scientific paper
May 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981apj...245..857d&link_type=abstract
Astrophysical Journal, Part 1, vol. 245, May 1, 1981, p. 857-865.
Astronomy and Astrophysics
Astronomy
122
H Ii Regions, Interstellar Gas, Interstellar Masers, Ionized Gases, Nebulae, Water Masers, Cosmic Dust, Cosmic Plasma, Electron Density (Concentration), Electron Energy, Far Infrared Radiation, Infrared Spectra, Main Sequence Stars, Radio Sources (Astronomy), Stellar Envelopes
Scientific paper
Observations of the compact H II region W3 (OH), one of the youngest H II regions in the Galaxy, made with the VLA at 2 and 1.3 cm with an angular resolution of approximately 0.2 arcsec are reported. Maps obtained reveal the ultracompact H II region to be a dense shell which only starts to become optically thin at 1.3 cm, with outer diameter 5.9 x 10 to the 16th cm, thickness approximately 0.9 x 10 to the 16th cm, mean electron density approximately 220,000/cu cm and electron temperature approximately 9400 K. Accurate positions are also obtained for the nearby water vapor masers, which were determined to have continuum upper limits of 4.2 and 10.5 mJy at 2 and 1.3 cm, respectively. The far infrared and radio luminosities indicate that the H II region is excited by a main sequence O7 star, and is surrounded by a cold dust cloud of central UV optical depth of 100, radius 1.7 x 10 to the 18th cm and mass 100 solar masses. The shell is interpreted as the ionized inner edge of a dust-enriched cocoon which formed around the star in its protostellar stage. An upper limit of 270 years is derived for the age of the H II region.
Dreher John W.
Welch William J.
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