NOAO > Observing Info > Approved Programs > 2004A-0059
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NOAO > Observing Info > Approved Programs > 2004A-0059 |
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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
Title: Chemical Abundances in Nebulae: Integrated Absorption and Emission-Line Analysis
Abstract:
Serious discrepancies have arisen in CNONe abundances determined
from forbidden vs. permitted emission lines for galactic nebulae. The
cause of the discrepancies, which can exceed an order of magnitude for
some PNe, 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 currently exist for only one object,
IC 418. We have been awarded cycle 12 HST time to obtain UV spectra of
four PNe central stars with STIS that will provide data necessary to
exploit this new technique. Here we propose for 3 nights of 2.1m time
to obtain the necessary ground-based measurements of the strengths of
optical-passband emission lines of NGC 6543, the one northern-hemisphere
object in this sample. As a secondary program, we will also observe NGC
7027 to calibrate our existing KPNO echelle spectra of this object.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360
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NOAO > Observing Info > Approved Programs > 2004A-0059 |
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