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Water vapor in the Orion Molecular CloudInfrared observations of interstellar gas-phase H2O in the spectrum of the BN object in Orion are reported. There are absorptions (S/N = 2-5) at the positions of four of the strong lines in the 000-001 nu3 vibration-rotation band. With an estimated excitation temperature of 150 K, the column density of gaseous H2O toward BN in the OMC-1 cloud is (2 + or - 1) x 10 to the 17th/sq cm. The intensities of the lines imply an ortho/para ratio of 1 + or - 0.5 indicating recent sublimation of H2O from low-temperature grains. The results give gas-phase abundance ratios of H2O/CO roughly 0.03 + or - 0.02 and HDO/H2O = 0.001-0.0001 toward BN. The velocities of the H2O absorptions agree with those of the ridge source and CO outflow, but the position along the line of sight is not well constrained. The gas/solid ratio is H2O(gas)/H20(ice) = 0.05 or less. Less than 1 percent of the oxygen is in H2O gas (assuming total cosmic abundance). Most of the H2O in the line of sight to BN, and by inference in quiescent regions of molecular clouds generally, is frozen on grains.
Document ID
19910037143
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Knacke, R. F.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Larson, H. P.
(Arizona, University Tucson, United States)
Date Acquired
August 15, 2013
Publication Date
January 20, 1991
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 367
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
91A21766
Funding Number(s)
CONTRACT_GRANT: NAG2-495
CONTRACT_GRANT: NAG2-206
Distribution Limits
Public
Copyright
Other

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