Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993apj...417..613z&link_type=abstract
Astrophysical Journal v.417, p.613
Astronomy and Astrophysics
Astronomy
26
Ism: Molecules, Ism: Individual Alphanumeric: S140, Radio Lines: Ism
Scientific paper
The S140 molecular cloud was observed in the NH3 (1, 1) and (2, 2) lines with 5" resolution. Compared with the previous VLA observations, the new observations have 3 times better flux sensitivity, 4 times better spatial resolution, and 2.5 times better velocity resolution. These advantages allowed the detection of 80%-85% of the single-dish flux in the two NH3 lines. The NH3emission region consists of a long filament perpendicular to the optical bright rim and an arclike structure along the edge of the bright rim. Within 15" of IRS 1, there is an absence of NH3emission which is probably caused by a true decrease in NH3 column density, not by missing short spacings or changes in the partition function due to a temperature increase. Comparison with a multitransition analysis of CS observations shows that this low NH3 column density indicates a low NH3 abundance in the dense gas near the infrared sources rather than an absence of molecular gas. The gas temperature is derived from the NH3 data and can be accounted for mostly by heating from IRS 1-IRS 3. We also detected a compact continuum source at 2.7 mm with the Owens Valley Millimeter Interferometer. This continuum source coincides with the peak of low-J CS emission and an NH3 emission peak. The NH3 lines at this position are unusually wide, and the profiles are consistent with models of gravitational collapse.
Evans Neal J. II
Kutner Marc L.
Mundy Lee G.
Zhou Shudong
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