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2005MNRAS.362..424W - Mon. Not. R. Astron. Soc., 362, 424-454 (2005/September-2)
The abundance discrepancy - recombination line versus forbidden line abundances for a northern sample of galactic planetary nebulae.
WESSON R., LIU X.-W. and BARLOW M.J.
Abstract (from CDS):
Elemental abundances are derived for the sample nebulae from both CELs and optical recombination lines (ORLs). ORL abundances are higher than CEL abundances in every case, by factors ranging from 1.5 to 12. Five objects with O2+ abundance discrepancy factors greater than 5 are found. DdDm 1 and Vy 2-2 are both found to have a very large abundance discrepancy factor of 11.8.
We consider the possible explanations for the observed discrepancies. From the observed differences between Te(Oiii) and Te(BJ), we find that temperature fluctuations cannot resolve the abundance discrepancies in 22 of the 23 sample nebulae, implying some additional mechanism for enhancing ORL emission. In the one ambiguous case, the good agreement between abundances derived from temperature-insensitive infrared lines and temperature-sensitive optical lines also points away from temperature fluctuations being present. The observed recombination line temperatures, the large abundance discrepancies and the generally good agreement between infrared and optical CEL abundances all suggest instead the existence of a cold hydrogen-deficient component within the `normal' nebular gas. The origin of this component is as yet unknown.
Abstract Copyright: 2005 RAS
Journal keyword(s): ISM: abundances - planetary nebulae: general
Simbad objects: 36
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