Other
Scientific paper
Jun 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...428..219z&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 428, no. 1, p. 219-232
Other
39
Astronomical Models, Carbon Compounds, Density Distribution, H Ii Regions, Interstellar Gas, Molecular Clouds, Star Formation, Cosmic Dust, Early Stars, Radiative Transfer, Temperature Distribution, Virial Theorem
Scientific paper
The S140 molecular cloud was observed in five transitions of CS with resolutions of 11 to 45 arcsec. The data were analyzed with both the LVG and microturbulent models of radiative transfer to derive the density structure. It was found that the CS emission comes from three components of gas: a spherical component centered on the infrared cluster, an arc component along the ionization front between the S140 H II region and the dense molecular cloud core, and a high-velocity component from the dense part of a molecular outflow. The spherical component contributes most to the CS emission and was analyzed in more detail than the other components. Using a temperature distribution derived from an analysis of the dust emission from S140, we fit a power-law density distribution of n(r) = ni(r/ri)-alpha to the spherical component. The best fit was for ni = 1.4 x 106 (density at ri = 0.026 pc) and alpha = 0.8. The density (ni) was found to be greater than or equal to the density required to account for the dust emission, depending on the dust opacity laws adopted. The presence of optical emission (Dinerstein, Lester, & Rank 1979) suggests a clumpy structure for the dense gas. Considerations of the virial mass and the lowest amount of column density required to produce dust emission put the volume filling factor (fnu) of the dense gas at approximately 0.14-0.5. We compared S140 with other regions of star formation where the density structure has been derived from excitation analysis. Source-source variations in density gradients and clumpiness clearly exist, ranging from alpha = 2 and fnu approximately 1 in B335 to alpha approximately 0, fnu approximately 0.1 in M17. There is a tendency for more massive star-forming regions to have a flatter density distribution, a more clumpy structure, and a large number of young stars. The implications of this tendency are discussed.
Butner Harold M.
Evans Neal J. II
Guesten Rolf
Kutner Marc L.
Mundy Lee G.
No associations
LandOfFree
CS multitransitional study of density distribution in star-forming regions. 2: The S140 region does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with CS multitransitional study of density distribution in star-forming regions. 2: The S140 region, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and CS multitransitional study of density distribution in star-forming regions. 2: The S140 region will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1862820