INFRARED ARRAY PHOTOMETRY OF METAL-RICH GLOBULAR-CLUSTERS .2. LILLER-1 - THE MOST METAL-RICH CLUSTER

We present the first color-magnitude diagram of Liller 1, a globular cluster with an angular separation of only 5° from the galactic center and a latitude of 0.2°. We estimate a metallicity for this cluster of [Fe/H]=+0.25±0.3 based on the slope of Liller 1's giant branch in the near-infrared. This implies that Liller 1 is the most metal rich galactic globular cluster known. Any reasonable uncertainty in the age of the cluster will not affect our method for deriving the metallicity. We also conclude that for Liller 1 E(J-K)=1.70±0.06 (or AV≈9.5) and (m-M)0=14.68±0.23. The atypical JHK colors of the Liller 1 stars, the extreme slope of its giant branch, and its physical closeness to the galactic center raise the question of whether it is a normal globular cluster or if its formation and evolution have been strongly influenced by its proximity to the galactic center.