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The optical depth of the 158 micrometer (C-12 II) line: Detection of the F=1 yields 0 (C-13 III) hyperfine-structure componentThe first detection of the F = 1 yields 0 hyperfine component of the 158 micrometer (C-13 II) fine structure line in the interstellar medium is reported. A twelve point intensity map was obtained of the (C-13 II) distribution over the inner 190 inch (right ascension) by 190 inch (declination) regions of the Orion nebula using an imaging Fabry-Perot interferometer. The (C-12 II)/(C-13 II) line intensity ratio varied significantly over the region mapped. It is highest (86 plus or minus 9) in the core of the Orion H II region and significantly lower (62 plus or minus 7) in the outer regions of the map, reflecting higher optical depth in the (C-12 II) line here. It is suggested that this enhanced optical depth is the result of limb brightening of the optically thin (C-13 II) line at the edges of the bowl-shaped H II region blister. If the C-12/C-13 abundance ratio is 43, the (C-12 II) line in the inner regions of the Orion nebula, has a low optical depth: tau sub 12 approximately = 0.75 plus or minus 0.25. The optical depth together with the large brightness temperature of the (C-12 II) line (approximately 160 K) requires that the excitation temperature of the P-2 sub 3/2 level be approximately 310 K, in very good agreement with the previous analysis of the physical conditions of the Orion interface region based on fine structure line intensity ratios and photodissociation region models. If the C-12/C-13 abundance ratio is 67, the line optical depth is somewhat larger (tau sub 12 approximately = 1.85), and the transition excitation temperature is somewhat smaller (approximately 190 K) than that predicted by these models. The present results therefore support values approximately = 43 for the C-12/C-13 abundance ratio in the Orion nebula.
Document ID
19920013061
Acquisition Source
Legacy CDMS
Document Type
Preprint (Draft being sent to journal)
Authors
Stacey, G. J.
(California Univ. Berkeley., United States)
Townes, C. H.
(California Univ. Berkeley., United States)
Poglitsch, A.
(Max-Planck-Gesellschaft Garching (Germany, F.R.)., United States)
Madden, S. C.
(Max-Planck-Gesellschaft Garching (Germany, F.R.)., United States)
Jackson, J. M.
(Boston Univ. MA., United States)
Herrmann, F.
(Max-Planck-Gesellschaft Garching (Germany, F.R.)., United States)
Genzel, R.
(Max-Planck-Gesellschaft Garching (Germany, F.R.)., United States)
Geis, N.
(California Univ. Berkeley., United States)
Date Acquired
September 6, 2013
Publication Date
October 1, 1991
Subject Category
Astronomy
Report/Patent Number
NASA-CR-190255
NAS 1.26:190255
MPE-PREPRINT-211
Accession Number
92N22304
Funding Number(s)
CONTRACT_GRANT: NAG2-208
Distribution Limits
Public
Copyright
Other
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