NOAO >   Observing Info >   Approved Programs >   2003B-0154

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Proposal Information for 2003B-0154


PI: Horace Smith, Michigan State University, smith@pa.msu.edu
Address: Physics Department, Biophysical Sciences Building, East Lansing, MI 48824, USA

CoI: Gisella Clementini, Osservatorio Astronomico di Bologna
CoI: Marcio Catelan, Pontificia Universidad Catolica de Chile
CoI: Ennio Poretti, Osservatorio Astronomico di Brera
CoI: Enrico Held, Osservatorio Astronomico di Padova
CoI: Barton Pritzl, NOAO

Title: The Oosterhoff Phenomenon in Globular Clusters of the Fornax Dwarf Spheroidal Galaxy

Abstract: We propose to identify and obtain periods and light curves for RR Lyrae variable stars within the five globular clusters of the Fornax dwarf spheroidal galaxy. This can be achieved from the ground using the 4-m MOSAICII imager and the image subtraction package ISIS. With such data we will determine whether the Fornax globular clusters conform to the Oosterhoff dichotomy shown by Galactic globular clusters. If they do not, then the Galactic globular cluster system cannot have been assembled from clusters in a Fornax-like protogalactic fragment. Moreover, the universal nature of the Oosterhoff dichotomy is essential in establishing the universality of the horizontal-branch luminosity- metallicity relationship, and therefore of the Population II distance scale. In the process of observing the clusters, we will also be able to obtain periods and light curves for variable stars in the field of Fornax. The wide field of the imager will allow us to detect any gradients in the variable star populations of the field. Also, given that Fornax is the only dwarf spheroidal galaxy known to contain Population II Cepheids, we will be able to compare the distance estimates from the RR Lyrae, Anomalous Cepheids, and Population II Cepheids. The general properties of the variable stars will also be compared to other dwarf spheroidals.


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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