NOAO >   Observing Info >   Approved Programs >   2005A-0099

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Proposal Information for 2005A-0099


PI: Jack Baldwin, Michigan State University, baldwin@pa.msu.edu
Address: Physics Department, 3270 Biomedical Physical Sciences Building, East Lansing, MI 48824, USA

CoI: Robert Williams, Space Telescope Science Institute
CoI: Edward Jenkins, Princeton University
CoI: Eric Pellegrini, Michigan State University
CoI: Mark Phillips, Las Campanas Observatory

Title: Chemical Abundance Discrepancies in Nebulae: A high dispersion UV/optical spectroscopic study.

Abstract: Serious discrepancies, often exceeding an order of magnitude, have arisen in CNONe abundances determined from forbidden vs. permitted emission lines for galactic nebulae. The cause has been studied intensively, but is still unknown. Emission line abundances cannot be considered reliable until the nature of these contradictory results is understood. We have developed a technique for integrating absorption lines into emission analyses for diffuse nebulae that provides an independent check on the validity of emission-line analyses. It requires high resolution observations of UV resonance absorption produced by the nebular gas in front of embedded or background stars together with forbidden emission line strengths from optical spectra. Such observations previously existed for only one object. To extend this to a larger sample, we obtained high-quality HST UV echelle spectra of four additional PNe central stars to measure the nebular absorption lines. To try to measure the necessary emission lines, we also obtained intermediate-resolution ground-based spectra with the DuPont Telescope in Chile and the KPNO 2.1m. However, some of the emission lines prove to be quite faint and/or blended, so higher wavelength resolution on a bigger telescope is needed. Here we propose for KPNO 4m time to observe NGC 6543, the one northern-hemisphere (+66\deg) object in this sample.


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NOAO >   Observing Info >   Approved Programs >   2005A-0099

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