NOAO >   Observing Info >   Approved Programs >   2010A-0173

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Proposal Information for 2010A-0173


PI: Ian U. Roederer, University of Texas, iur@astro.as.utexas.edu
Address: Department of Astronomy, 1 University Station C1400, Austin, TX 78712, USA

CoI: Christopher Sneden, University of Texas

Title: Characterizing the Age and Chemical Enrichment of the Heaviest Elements in Globular Cluster M92

Abstract: We propose to derive detailed abundances for the heaviest elements, which are produced by neutron captures, in ~ 50 stars in the very metal-poor globular cluster M92 using the Hydra multi-object spectrograph on WIYN. This chemical information will reveal (1) which neutron-capture process(es) have produced the heavy metals, (2) the star- to-star dispersion of bulk enrichment levels, and (3) an age for M92 measured from the radioactive decay of the element thorium. Early evidence suggests the rapid neutron-capture process produced the heaviest elements in M92; confirming this and establishing the level of dispersion would place constraints on enrichment mechanisms. Measurement of the age from ~ 50 stars will constrain the age with a precision of approx. 1.5 Gyr, improving on the precision of the current radioactive age estimate, which is 4-6 Gyr. This approach- targeting many stars to manage the statistical uncertainty on the thorium abundance-has not been attempted before in any halo stars or globular clusters, but if successful it could be applied to a number of other metal-poor clusters and provide a powerful cross-check on ages derived from other methods.


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NOAO >   Observing Info >   Approved Programs >   2010A-0173

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