Volume 429, Number 1, January I 2005
|Page(s)||181 - 192|
|Section||Interstellar and circumstellar matter|
|Published online||13 December 2004|
III. The gas depletion
LERMA & UMR 8112 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France e-mail: email@example.com
2 Instituto de Estructura de la Materia, Dpto de Física Molecular CSIC, Madrid, Spain
3 University of Arizona, Steward Observatory, 933 N. Cherry Ave., Tucson, AZ 85721, USA
4 Observatoire de Bordeaux, BP 89, 33270 Floirac, France
Accepted: 27 July 2004
We present a detailed study of the gas depletion in L183 (= L134N) for a set of important species, namely, CO, CS, SO, N2H+and NH3. We show that all these species are depleted at some level. This level seems to depend mostly on a density threshold rather than on dust opacity. Therefore UV shielding would not be a main factor in the triggering of depletion. Our data suggest that CO, CS and SO depletion happen at densities of ~3 104 cm-3, while N2H+and NH3 seem to deplete at densities close to 106 cm-3. The latter result is consistent with the Bergin & Langer ([CITE], ApJ, 486, 316) polar (H2O) ice case but not with the more recent models of Aikawa et al. ([CITE], ApJ, 593, 906). CS depletion occurs much below its (J:2–1) critical density, (7 105 cm-3) and therefore makes this species unsuitable to study the density structure of many dark cloud cores.
Key words: ISM: abundances / ISM: molecules / ISM: dust, extinction / ISM: individual: objects: L183 (L134N) / radio lines: ISM
© ESO, 2005
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