Metal-rich globular clusters : giant branch morphology as a metallicity Criterion

Abstract

We have obtained VI CCD photometry of the very metal-rich inner bulge globular clusters NGC 6528, NGC 6553 and Ter 1, and of 47 Tuc and NGC 6356, which are usually called metal-rich clusters. We discuss the RGB morphology in the V vs. (V-I) and I vs. (V-I) diagrams for ranking the metallicities of these clusters. We used the arc-like structure present in their RGB, due to blanketing in the cooler giants, as a metallicity criterion, which is corroborated by line strengths in integrated spectra. We propose criteria of morphological parameters based on RGB inclination for increasing metallicities. We conclude that Terzan 1 is the most metal-rich globular cluster of this sample.