The Excitation of SO in Cold Molecular Clouds: TMC-1

Details The Excitation of SO in Cold Molecular Clouds: TMC-1 The Excitation of SO in Cold Molecular Clouds: TMC-1

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006apj...653.1342l&link_type=abstract

The Astrophysical Journal, Volume 653, Issue 2, pp. 1342-1352.

Astronomy and Astrophysics

Astronomy

21

Ism: Abundances, Ism: Individual: Alphanumeric: Tmc-1, Ism: Molecules, Molecular Processes

Scientific paper

We have performed calculations on the excitation of SO using the accurate collisional rate coefficients at low temperatures for the system SO-He recently published by Lique et al. Compared with the results of Green, the new excitation rates show significant differences for transitions involving the low energy levels. We present a set of radiative transfer models for different cloud geometries and physical conditions, using the new rate coefficients for SO, and show that they provide a more correct diagnostic of the physical conditions of cold dark clouds. We have applied these results to observations of mapping results in TMC-1 done in the 23-12, 34-23, and 22-11 transitions (using the IRAM 30 m telescope) and the 01-10 transition (using the 100 m Effelsberg radio telescope). The intensity maxima for all these lines is found around the so-called ammonia peak. The structure of TMC-1 is well represented by a cylindric filament with several cores [TK=8 K, n(H2)~3×104 cm-3] surrounded by an envelope [TK=10 K, n(H2)~(6-8)×103 cm-3] showing a complex velocity structure. The abundance of SO in TMC-1 is nearly constant along the filament, X(SO)~=10-8, except at the ammonia peak, where a higher SO abundance, X(SO)~=2.5×10-8, is required.

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