Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001noao.prop..202w&link_type=abstract
NOAO Proposal ID #2001B-0202
Astronomy and Astrophysics
Astrophysics
Scientific paper
We are investigating the worrisome difference between the chemical abundances determined from classical forbidden-line analysis in HII regions, and those determined for the same objects using permitted recombination lines of the heavy elements. Using these two different methods leads to as much as an order of magnitude discrepancy. Our approach is to make a very detailed analysis of a few objects with especially simple geometry, paying great attention to identifying which permitted lines really are due to recombination and come from the same gas volume elements as the forbidden lines to which they are being compared. Here we request time to obtain 10 km/sec echelle spectra of two southern planetary nebulae, selected on the basis of their simple geometry and high surface brightness. We need to measure weak permitted lines down to 10^5 times fainter than H(beta), and to compare their velocity profiles. The basic goal of this project is to assess and hopefully improve the general accuracy of abundance determinations made from studying emission-line regions in their many astrophysical settings.
Baldwin Jack
Sharpee Brian
Williams Robert
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