A Near-Infrared Photometric Survey of Metal-Poor Inner Spheroid Globular Clusters and Nearby Bulge Fields

Abstract

Images recorded through J, H, K, 2.2 micron continuum and CO filters have been obtained of a sample of metal-poor ([Fe/H] < -1.3) globular clusters in the inner spheroid of the Galaxy. The shape and color of the upper giant branch on the (K, J-K) CMD, combined with the K brightness of the RGB-tip, are used to estimate the metallicity, reddening, and distance of each cluster. CO indices are used to identify bulge stars, which will bias metallicity and distance estimates if not removed from the data. Bulge fields were also observed near each cluster. The slope of the bulge giant branch luminosity function does not vary between most fields, although the LFs in Baade's Window and near NGC 6273 are significantly shallower than average. The data also suggest that the HB content may not be uniform throughout the bulge, in the sense that a larger than average number of red HB stars may occur in fields closest to the Galactic Center.