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Discovery of Interstellar Hydrogen FluorideWe report the first detection of interstellar hydrogen fluoride. Using the Long Wavelength Spectrometer of the Infrared Space Observatory (ISO), we have detected the 121.6973 micron J = 2-1 line of HF in absorption toward the far-infrared continuum source Sagittarius B2. The detection is statistically significant at the 13 sigma level. On the basis of our model for the excitation of HF in Sgr B2, the observed line equivalent width of 1.0 nm implies a hydrogen fluoride abundance of about 3 x 10 (exp -10) relative to H, If the elemental abundance of fluorine in Sgr B2 is the same as that in the solar system, then HF accounts for about 2% of the total number of fluorine nuclei. We expect hydrogen fluoride to be the dominant reservoir of gas-phase fluorine in Sgr B2, because it is formed rapidly in exothermic reactions of atomic fluorine with either water or molecular hydrogen; thus, the measured HF abundance suggests a substantial depletion of fluorine onto dust grains. Similar conclusions regarding depletion have previously been reached for the case of chlorine in dense interstellar clouds. We also find evidence at a lower level of statistical significance (about 5 sigma) for an emission feature at the expected position of the 4(sub 32)-4(sub 23) 121.7219 micron line of water. The emission-line equivalent width of 0.5 mm for the water feature is consistent with the water abundance of 5 x 10(exp -6) relative to H, that has been inferred previously from observations of the hot core of Sgr B2.
Document ID
20000088619
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Neufeld, David A.
(Johns Hopkins Univ. Baltimore, MD United States)
Zmuidzinas, Jonas
(California Inst. of Tech. Pasadena, CA United States)
Schilke, Peter
(Max-Planck-Inst. fuer Radioastronomie Bonn, Germany)
Phillips, Thomas G.
(California Inst. of Tech. Pasadena, CA United States)
Date Acquired
August 19, 2013
Publication Date
October 20, 1997
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society
Volume: 488
Issue: 2
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: NAG2-744
CONTRACT_GRANT: NSF AST-96-15025
CONTRACT_GRANT: NAGW-3147
CONTRACT_GRANT: NAG5-3316
Distribution Limits
Public
Copyright
Other

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