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1999ApJ...518..760K - Astrophys. J., 518, 760-768 (1999/June-3)
CO observations of the W51B H II region complex.
KOO B.-C.
Abstract (from CDS):
We derive CO J=2-1/J=1-0 luminosity ratios of 1.2 and 1.4 for these clouds, which are much higher than typical ratios (0.5-0.8) for nearby molecular clouds. Based on the large observed ratios and existing 13CO results, we propose that the W51B clouds are externally heated by far-ultraviolet radiation and that the 12CO lines originate from the photodissociation regions on the surfaces of dense (≳104 cm–3) clumps. We estimate the filling factors of these clumps to be small (<0.1). Our results further suggest that the clouds do not have low-density envelopes, which could have been destroyed by UV photons and stellar winds from nearby OB stars. We estimate that the star formation efficiency (SFE) of the W51B region is very high, i.e., 7% and 15% for clouds NE and SW, respectively. The very high SFE could be due to enhanced star formation by the spiral density wave.
Abstract Copyright: ∼
Journal keyword(s): H II regions - ISM: Clouds - ISM: individual (W51) - ISM: Molecules - Radio Lines: ISM - Stars: Formation
Simbad objects: 21
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