NOAO >   Observing Info >   Approved Programs >   2010B-0230

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Proposal Information for 2010B-0230


PI: Alistair Walker, NOAO/CTIO, awalker@ctio.noao.edu
Address: Casilla 603, La Serena, Chile

CoI: Gloria Andreuzzi, INAF-Telescopio Nazionale Galileo
CoI: Giuseppe Bono, Universita Tor Vergata de Roma
CoI: Alessandra Di Cecco, Universita Tor Vergata de Roma
CoI: Andrea Kunder, NOAO/CTIO
CoI: Peter Stetson, Hertzberg Institute of Astrophysics

Title: Multipopulations in NGC 2808: helium or not helium?

Abstract: Galactic globular clusters, almost without exception, have long been thought to be excellent examples of simple stellar populations. However, from HST photometry, many have been shown to exhibit multiple populations, but the diversity shown and observational difficulties mean that we are far from a definitive consensus for explaining the early evolution and enrichment history for globulars. Here we plan to collect accurate and deep NIR (J,K) images for the galactic globular cluster NGC 2808. The new images together with optical (B,V,I) data already available to our group will allow us to constrain the nature of the multiple populations detected in this stellar system. A popular working hypothesis is that they are caused by the stars in each population having different helium abundances, attributed to successive enhancements from multiple bursts of star formation in the early life of the cluster. However so far all evidence to support this scenario is indirect. We will test this, with the key advantage of our observational strategy being that optical-NIR (V-K, B-K) colors are a factor of two more sensitive to an increase in helium than optical (V-I, B-I) colors.


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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