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Abundances of Refractory Elements in the Orion Nebula

Published online by Cambridge University Press:  07 August 2017

R. H. Rubin ,
E. F. Erickson ,
M. R. Haas ,
S.W.J. Colgan ,
J. P. Simpson  and
R. J. Dufour
R. H. Rubin
Affiliation:
NASA Ames Research Center, M.S. 245 − 6, Moffett Field, CA 94035 USA.
E. F. Erickson
Affiliation:
NASA Ames Research Center, M.S. 245 − 6, Moffett Field, CA 94035 USA.
M. R. Haas
Affiliation:
NASA Ames Research Center, M.S. 245 − 6, Moffett Field, CA 94035 USA.
S.W.J. Colgan
Affiliation:
NASA Ames Research Center, M.S. 245 − 6, Moffett Field, CA 94035 USA.
J. P. Simpson
Affiliation:
NASA Ames Research Center, M.S. 245 − 6, Moffett Field, CA 94035 USA.
R. J. Dufour
Affiliation:
Dept. Space Physics & Astronomy, Rice University, Houston, TX 77251 USA.

Abstract

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We assess the gas-phase abundances of Si, C, and Fe from our recent measurements of Si++, C++, and Fe++ in the Orion Nebula by expanding on our earlier “blister” models. The Fe++ 22.9 μm line measured with the KAO yields Fe/H ~ 3 × 10−6 - considerably larger than in the diffuse ISM, where relative to solar, Fe/H is down by ~ 100. However, in Orion, Fe/H is still lower than solar by a factor ~ 10. The C and Si abundances are derived from new IUE high dispersion spectra of the C++ 1907, 1909 Å and Si++ 1883, 1892 Å lines. Gas-phase Si/C = 0.016 in the Orion ionized volume and is particularly insensitive to uncertainties in extinction and temperature structure. The solar value is 0.098. Gas-phase C/H = 3 × 10−4 and Si/H = 4.8 × 10−6. Compared to solar, Si is depleted by 0.135 in the ionized region, while C is essentially undepleted. This suggests that most Si and Fe resides in dust grains even in the ionized volume.

Type
Quiescent Clouds and Regions of Star Formation
Information
Symposium - International Astronomical Union , Volume 150: Astrochemistry of Cosmic Phenomena , 1992 , pp. 281 - 283
Copyright
Copyright © Kluwer 1992 

References

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