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Abundances of ethylene oxide and acetaldehyde in hot molecular cloud coresWe have searched for millimetre-wave line emission from ethylene oxide (c-C2H4O) and its structural isomer acetaldehyde (CH3CHO) in 11 molecular clouds using SEST. Ethylene oxide and acetaldehyde were detected through multiple lines in the hot cores NGC 6334F, G327.3-0.6, G31.41+0.31, and G34.3+0.2. Acetaldehyde was also detected towards G10.47+0.03, G322.2+0.6, and Orion 3'N, and one ethylene oxide line was tentatively detected in G10.47+0.03. Column densities and rotational excitation temperatures were derived using a procedure which fits the observed line intensifies by finding the minimum chi 2-value. The resulting rotational excitation temperatures of ethylene oxide and acetaldehyde are in the range 16-38 K, indicating that these species are excited in the outer, cooler parts of the hot cores or that the excitation is significantly subthermal. For an assumed source size of 20", the deduced column densities are (0.6-1)x10(14) cm-2 for ethylene oxide and (2-5)x10(14) cm-2 for acetaldehyde. The fractional abundances with respect to H2 are X[c-C2H4O]=(2-6)xl0(-10), and X[CH3CHO]=(0.8-3)x10(-9). The ratio X[CH3CHO]/X[c-C2H4O] varies between 2.6 (NGC 6334F) and 8.5 (G327.3-0.6). We also detected and analysed multiple transitions of CH3OH, CH3OCH3, C2H5OH, and HCOOH. The chemical, and possibly evolutionary, states of NGC 6334F, G327.3-0.6, G31.41+0.31, and G34.3+0.2 seem to be very similar.
Document ID
20040088943
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Nummelin, A.
(Onsala Space Observatory Sweden)
Dickens, J. E.
Bergman, P.
Hjalmarson, A.
Irvine, W. M.
Ikeda, M.
Ohishi, M.
Date Acquired
August 21, 2013
Publication Date
September 1, 1998
Publication Information
Publication: Astronomy and astrophysics
Volume: 337
Issue: 1
ISSN: 0004-6361
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: NAG5-3653
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Exobiology

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