Wide Field Near-Infrared Photometry of 12 Galactic Globular Clusters:
  Observations Versus Models on the Red Giant Branch
  We present wide field near-infrared photometry of 12 Galactic globular
clusters, typically extending from the tip of the cluster red giant branch
(RGB) to the main sequence turnoff. Using recent homogenous values of cluster
distance, reddening and metallicity, the resulting photometry is directly
compared to the predictions of several recent libraries of stellar evolutionary
models. Of the sets of models investigated, Dartmouth and Victoria-Regina
models best reproduce the observed RGB morphology, albeit with offsets in J-Ks
color which vary in their significance in light of all sources of observational
uncertainty. Therefore, we also present newly recalibrated relations between
near-IR photometric indices describing the upper RGB versus cluster iron
abundance as well as global metallicity. The influence of enhancements in alpha
elements and helium are analyzed, finding that the former affect the morphology
of the upper RGB in accord with model predictions. Meanwhile, the empirical
relations we derive are in good agreement with previous results, and minor
discrepancies can likely be attributed to differences in the assumed cluster
distances and reddenings. In addition, we present measurements of the
horizontal branch (HB) and RGB bump magnitudes, finding a non-negligible
dependence of the near-IR HB magnitude on cluster metallicity. Lastly, we
discuss the influence of assumed cluster distances, reddenings and
metallicities on our results, finding that our empirical relations are
generally insensitive to these factors to within their uncertainties.
