JHK Photometry in Metal Rich Globulars.

These data begin near the top of the giant branch (GB) and extend to stars six magnitudes fainter, reaching below the horizontal branch (HB). We use our sample and previously published data for two other clusters, 47 Tucanae and M69, to develop techniques for deriving basic properties such as metallicity and distance modulus from observable parameters of cluster color-magnitude diagrams (CMDs) in the near-IR.

We also analyze the horizontal branches of the clusters in an attempt to set constraints on mass loss for first-ascent giants. We find that the slope of the linear fit to the GB stars brighter than the HB can be used to predict metallicity to an accuracy of +/- 0.25 dex for clusters with [Fe/H] between -1.0 and -0.3. There appears to be no significant dependence on [Fe/H] for other reddening-free indices measured from the CMD, including the width of the HB and the separation between the GB and HB at the level of the HB.