Metallicity Determinations for Globular Clusters through Spectrophotometry of Their Intergrated Light

Using an appropriately weighted combination of 16 indices of absorption line strength measured in low-dispersion spectra of the integrated light of globular clusters, metallicities Fe/H are determined for thirty-six clusters in the Galaxy. The results confirm the suggestion that Zinn's (1980) scale suffers a systematic error in the region of intermediate metallicity and support an explanation in which his metallicity-indicative Q39 index has been diluted by excess ultraviolet light in clusters with anomalously rich blue horizontal branches. The methods, which involve the measurement of spectral features arising from many species, produce estimates of metallicity which are insensitive to this problem. Good agreement is found with several recent studies, but a disagreement is noted for the most metal-rich clusters studied by Frogel, Cohen, and Persson (1983). Finally, a similar method with a modified calibration is used to determine metallicities for the nuclei of six galaxies.