NOAO >   Observing Info >   Approved Programs >   2006A-0222

Small NOAO Logo

Proposal Information for 2006A-0222


PI: Constantine P. Deliyannis, Indiana University, con@astro.indiana.edu
Address: Department of Astronomy, 727 E. 3rd Street, SW319, Bloomington, IN 47405-7105, USA

CoI: Barbara J. Anthony-Twarog, University of Kansas
CoI: Bruce A. Twarog, University of Kansas

Title: Spectroscopic Analysis of NGC 6253: The Most Metal-Rich Open Cluster?

Abstract: The open cluster NGC 6253 occupies a unique, but critically important, position in the parameter space of stellar populations within our Galaxy. Precise, CCD intermediate-band photometry of probable cluster members from the giant branch to below the turnoff suggests that this 3 Gyr-old cluster is the most metal-rich object ever observed in the disk, with an extrapolated [M/H] between +0.7 and +0.9, which could be a combination of [Fe/H] > +0.4 and enhanced light (alpha)- elements. NGC 6791 \it might have [Fe/H] as high as +0.4; \it all other reliably measured open clusters have [Fe/H] < +0.2 dex. We propose a spectroscopic survey of the cluster from the giant branch to the faintest known dwarfs using the CTIO 4m/HYDRA MOS. Three spectral regions (6715, 6330, 6100\AA) will yield numerous Fe I lines of varying (chi), some Fe II lines, and lines from Li, C, O, Si, Ca, Ni, Al, among others. Analysis will supply radial velocities for membership, a cluster velocity (an indication of the Milky Way population in which NGC 6253 resides), spectroscopic [Fe/H] and [X/Fe] for many key elements, and definitive proof of the first local example of a population type believed to exist in extragalactic systems such as giant ellipticals. Li abundances will explore a variety of key issues involving stellar interiors (do metal-rich dwarfs deplete more Li, as predicted? do metal- rich subgiants mix like their solar-Fe counterparts and unlike halo ones? does the origin of metal-rich blue stragglers involve mixing?) and Galactic chemical evolution (does Li production continue at super- solar [Fe/H]?).


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2006A-0222

noaoprop-help@noao.edu

Small NOAO Logo