NOAO > Observing Info > Approved Programs > 2001B-0211
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NOAO > Observing Info > Approved Programs > 2001B-0211 |
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PI: Andrew Dolphin, NOAO, dolphin@noao.edu
Address: Box 26732, Tucson, AZ 85726, USA
CoI: Abi Saha, NOAO
CoI: Evan Skillman, University of Minnesota
CoI: Jay Gallagher, University of Wisconsin
CoI: John Hoessel, University of Wisconsin
CoI: Ed Olszewski, University of Arizona
Title: Comparing the Primary Standard Candles in a Metal-Rich Galaxy: M31
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
calibrations are tied to statistical parallax distances to globular
clusters), a comparison between these indicates the degree of accuracy
to which they are known. One such intercomparison has recently been
done by us in the metal-poor galaxy IC 1613. M31 provides an ideal
complementary case, since it has a higher central metallicity comparable
to that of the galaxies observed in distance scale projects. When the
results for IC 1613 and M31 are combined, it will shed light on the
metallicity dependencies of the standard candles. While M31's Cepheid P-
L relation is well-established, there are large uncertainties regarding
its RR Lyrae p! opulation (both in terms of mean magnitude and number of
stars) that must be resolved before such a comparison can be made.
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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NOAO > Observing Info > Approved Programs > 2001B-0211 |
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