Carbon Isotopes in Planetary Nebulae and H II Regions

Grants and Contracts Details


-Ne propose to analyze all promising high dispersion rUE archive spectra of planetary nebulae (PNe) [ and H II regions to detect, or set upper limits to, the C III] 1909.6 A line produced by 13C. The intensity of the line emitted by rarer isotope, relative to the 12C III] 1908.7 A line directly measates he 13C/12C ratio in ionized gas. The 13C III] ion is able to emit in the J = 0 - 0, F = V2- 1J2transition [ (which is strictly forbidden in 12C III)) because of hyperfine interactions with the nuclear spin. IUE high resolution spectra are ideal for this purpose due to the relatively large throughput of its pectrometer when observing ex,ended sources, and because of the large database of high lispersion observations. e have examined the IUE archives and identified 366 high dispersion observations of planetary lebulae, and 93 observations of H II regions. We show sample spectra, and present an estimate of he signal to noise that should be present in the co-added spectra. Reasonable estimates are that he 13C/12C abundance ratio can be measured in many objects (although we will only know for ertain once the project is completed). In the case of Orion, this would allow a direct comparison letween the isotope ratio in the H II region and the molecular cloud from which it formed, a test of he effects of both chemical fractionation in the molecular cloud and the effects of the stellar wind on he composition of the H II region. In PNe this allows the effects of AGB evolution of the progenitor ,tar to be measured. This oroiect will imoact onaoina HST studies with similar aoals.
Effective start/end date3/15/033/14/04


  • National Aeronautics and Space Administration: $51,100.00


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