AAS 201st Meeting, January, 2003
Session 7. Globular Clusters and Their Contents
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[7.11] A New Age Measurement for Palomar 5

S. L. Martell, G. H. Smith (UCO/Lick Observatory, UC Santa Cruz), C. J. Grillmair (SIRTF Science Center, California Institute of Technology)

We present a new age measurement for the outer halo globular cluster Palomar 5, derived from HST V and I photometry (Grillmair & Smith 2001, AJ 122:3231). Using \alpha-dependent theoretical isochrones (Bergbusch & VandenBerg 2001, AJ 556:322) and a \chi2 minimization process allowing for variations in V-I and age, we explore the possible combinations of cluster age, metallicity, and \alpha-enhancement. We find that, assuming the parameters given in Vandenberg (2000, ApJS 129:315) ((m-M)V=16.85, E(V-I)=0.07, [Fe/H]=-1.41, [\alpha/Fe]=+0.3), the most likely age is 11.5±1 Gyr, in agreement with the age derived from ground-based B-V data (VandenBerg 2000). With the same distance modulus and reddening, but substituting the metallicity and \alpha-enhancement measured by high-dispersion Keck spectroscopy ([Fe/H]=-1.3, [\alpha/Fe]=0.2) (Smith et al 2001, AJ 123:1502), we find that the most likely age is still 11.5±1 Gyr. This work was supported by NASA through grant GO-06788.01-95A from the Space Telescope Science Institute.

The author(s) of this abstract have provided an email address for comments about the abstract: martell@ucolick.org

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