A New Globular Cluster Metallicity Scale Based on the Abundance of FeII

Abstract

When using Fe as a surrogate for ``metallicity'', the metallicity is best represented by the dominant species of Fe. Accordingly, we have derived a new globular cluster metallicity scale based on the equivalent widths of FeII lines measured from high resolution spectra of giant stars. The scale is primarily based on the results of analyses by the Lick-Texas group of 149 stars in 11 clusters, supplemented by other high resolution studies in five additional clusters. We also derive ab initio the true distance moduli for M3, M5, M13, M15, and M92 as a means of setting stellar surface gravities. We find that [Fe/H]II is correlated linearly with W', the reduced strength of the near-infrared CaII triplet defined by Rutledge et al (1997), although the correlation coefficients depend on the stellar atmosphere model employed. In addition to the 66 globular cluster metallicity estimates presented in a recent PASP review, we present here an additional 39 globular cluster metallicity estimates based on transformations from Q39, the photometric index defined by Zinn (1980).