Publication Date

2002

Journal or Book Title

ASTROPHYSICAL JOURNAL

Abstract

We present Submillimeter Wave Astronomy Satellite observations of water vapor in two cold starless clouds, B68 and core D in ρ Ophiuchi. Sensitive nondetections of the 110-101 transition of o-H2O are reported for each source. Both molecular cores have been previously examined by detailed observations that have characterized the physical structure. Using these rather well-defined physical properties and a Monte Carlo radiation transfer model, we have removed one of the largest uncertainties from the abundance calculation and set the lowest water abundance limit to date in cold low-mass molecular cores. These limits are x(o-H2O) < 3 × 10-8 (relative to H2) and x(o-H2O) < 8 × 10-9 in B68 and ρ Oph D, respectively. Such low abundances confirm the general lack of ortho-water vapor in cold (T < 20 K) cores. Provided that the ortho/para ratio of water is not near zero, these limits are well below theoretical predictions and appear to support the suggestion that most of the water in dense low-mass cores is frozen onto the surfaces of cold dust grains.

Comments

This is the pre-published version harvested from ArXiv. The published version is located at http://iopscience.iop.org/1538-4357/581/2/L105/

Volume

581

Pages

L105-L108

Issue

2

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