Water vapor in the Orion Molecular Cloud

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/169612· OSTI ID:6001070

Knacke, R F; Larson, H P ^[1]

---

1. NASA, Marshall Space Flight Center, Huntsville, AL (USA) Arizona Univ., Tucson (USA)

Infrared observations of interstellar gas-phase H{sub 2}O 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 H{sub 2}O 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 H{sub 2}O from low-temperature grains. The results give gas-phase abundance ratios of H{sub 2}O/CO roughly 0.03 + or - 0.02 and HDO/H{sub 2}O = 0.001-0.0001 toward BN. The velocities of the H{sub 2}O 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 H{sub 2}O(gas)/H{sub 2}O(ice) = 0.05 or less. Less than 1 percent of the oxygen is in H{sub 2}O gas (assuming total cosmic abundance). Most of the H{sub 2}O in the line of sight to BN, and by inference in quiescent regions of molecular clouds generally, is frozen on grains. 37 refs.

• OSTI ID: 6001070
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 367; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION
ABUNDANCE
ASTRONOMY
CHEMICAL COMPOSITION
CHEMISTRY
COSMIC GASES
COSMOCHEMISTRY
DENSITY
ELECTROMAGNETIC RADIATION
ELEMENT ABUNDANCE
FLUIDS
GASES
INFRARED RADIATION
INTERSTELLAR SPACE
MOLECULES
NEBULAE
PHYSICAL PROPERTIES
RADIATIONS
SPACE
VAPORS
WATER VAPOR