NOAO >   Observing Info >   Approved Programs >   2002A-0317

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Proposal Information for 2002A-0317


PI: K.B. Kwitter, Williams College, kkwitter@williams.edu
Address: 33 Lab Campus Drive, Williamstown, MA 01267, USA

CoI: R.B.C. Henry, U. of Oklahoma
CoI: Y.-H.Chu, U. of Illinois, Urbana-Champaign

Title: Does the S+Ar Abundance Track the Fe Abundance in the Interstellar Medium?

Abstract: The observed relation of O/Fe versus Fe/H for stars in the Galaxy over a wide range in metallicity is broadly used to constrain theoretical models of galactic chemical evolution. It would be extremely valuable to be able to test the behavior of this relation in other galaxies in order to confirm its universality. But since stars cannot currently be resolved in any but the most nearby systems, extending the analysis beyond the Galaxy will rely on identifying a combination of readily observable elements in bright H II regions which acts as a surrogate for Fe, whose lines are difficult to measure in nebulae. It has been suggested both on empirical and theoretical grounds that the S+Ar abundance tracks Fe, and the existence of such a relation would allow the O/Fe-Fe/H relation to be inferred directly in extragalactic nebulae where S and Ar may be easily measured. To begin to confirm this suggestion, we plan to obtain high-resolution spectroscopic observations of weak Fe lines in two Galactic planetary nebulae whose S and Ar abundances we have previously determined, one in the halo (DDDM-1), and one in the disk (M1-74). If the results bear out the predictions, we will expand our study to a larger sample for broader examination.


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