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Unraveling the 10 micron "silicate" feature of protostars: the detection of frozen interstellar ammoniaWe present infrared spectra of four embedded protostars in the 750-1230 cm-1 (13.3-8.1 microns) range. For NGC 7538 IRS 9, a new band is reported at 1110 cm-1 (9.01 microns, and several others may be present near 785, 820, 900, 1030, and 1075 cm-1 (12.7, 12.2, 11.1, 9.71, and 9.30 microns). The band 1110 cm-1 is attributed to frozen NH3. Its position and width imply that the NH3 is frozen in a polar, H2O-rich interstellar ice component. The NH3/H2O ice ratio inferred for NGC 7538 IRS 9 is 0.1, making NH3 as important a component as CH3OH and CO2 in the polar ices along this line of sight. At these concentrations, hydrogen bonding between the NH3 and H2O can account for much of the enigmatic low-frequency wing on the 3240 cm-1 (3.09 microns) H2O interstellar ice band. The strength of the implied NH3 deformation fundamental at 1624 cm-1 (6.158 microns) can also account for the absorption at this position reported by ISO.
Document ID
20040088931
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Lacy, J. H.
(University of Texas Austin 78712, United States)
Faraji, H.
Sandford, S. A.
Allamandola, L. J.
Date Acquired
August 21, 2013
Publication Date
July 1, 1998
Publication Information
Publication: The Astrophysical journal
Volume: 501
Issue: 1 Pt 2
ISSN: 0004-637X
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: AST-9618723
Distribution Limits
Public
Copyright
Other
Keywords
NASA Center ARC
NASA Discipline Exobiology

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