NOAO >   Observing Info >   Approved Programs >   2003A-0248

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Proposal Information for 2003A-0248


PI: Andrew Dolphin, NOAO, dolphin@noao.edu
Address: KPNO, PO Box 26732, Tucson, AZ 85726, USA

CoI: Abi Saha, NOAO
CoI: Evan Skillman, University of Minnesota
CoI: Frank Thim, NOAO

Title: Cepheids in the Sagittarius Dwarf Irregular Galaxy

Abstract: Our understanding of the extragalactic distance scale is limited in large part by uncertainties in the absolute magnitudes of the primary standard candles -- Cepheids and RR Lyraes. As these calibrations are largely independent (Cepheid calibrations are tied to the moving cluster distance to the Pleiades or an assumed LMC distance; RR Lyrae and RGB tip calibrations are tied to statistical parallax distances to globular clusters), a comparison between these indicates the degree of accuracy to which they are known. Dwarf irregular galaxies in the Local Group provide an ideal testing ground for the distance scales, as they contain stars of all ages at the same distance. They also provide large numbers of short-period Cepheids, which are common in low-metallicity star- forming galaxies and which we have recently demonstrated to be excellent standard candles. We propose to search for short-period Cepheids in SagDIG, which is likely the most metal-poor star-forming galaxy in the Local Group. A comparison between the distance measurements for this galaxy thus provides an important data point for understanding metallicity dependencies of the standard candles.


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 >   2003A-0248

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