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2004MNRAS.351.1026W - Mon. Not. R. Astron. Soc., 351, 1026-1042 (2004/July-1)
Physical conditions in the planetary nebula NGC 6543.
WESSON R. and LIU X.-W.
Abstract (from CDS):
We have obtained long-slit scanning spectra of NGC 6453, which, when combined with the total Hβ flux, give integrated fluxes for all the lines in our spectra. We determine ionic and total abundances within the nebula from both recombination lines and forbidden lines, and we find that recombination lines yield a higher abundance by a factor of approximately three. A temperature fluctuation parameter of 0.053 would resolve the discrepancy, but several factors argue against temperature fluctuations as the main cause: the value of t2 required is inconsistent with the results derived from the temperature map; the agreement of the temperatures derived from the hydrogen Balmer jump and [Oiii] line diagnostics also implies a low value of t2; and the agreement of abundances derived from temperature-insensitive infrared fine-structure lines and temperature-sensitive optical forbidden lines is inconsistent with the temperature fluctuation scenario.
We argue that a more likely explanation for the observed temperature and abundance discrepancies is the presence within the nebula of some hydrogen-deficient material at low temperatures. Weakly temperature-dependent line ratios of Hei and Oii imply lower temperatures than those found from forbidden-line temperature diagnostics and the hydrogen Balmer jump, as is expected in the presence of cold hydrogen-deficient material.
Abstract Copyright: 2004 RAS
Journal keyword(s): ISM: abundances - planetary nebulae: individual: NGC 6543
Simbad objects: 7
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