Near-infrared imaging of the central regions of metal-poor inner spheroid globular clusters

JHK images obtained with the Canada-France-Hawaii Telescope adaptive optics bonnette are used to investigate the near-infrared photometric properties of red giant branch (RGB) and horizontal-branch (HB) stars in eight metal-p oor globular clusters with R-GC less than or equal to 2 kpc. The slope of t he RGB on the (K, J-K) CMDs confirms the metal-poor nature of these cluster s, four of which (NGC 6287, 6293, 6333, and 6355) are found to have metalli cities that are comparable to M92. The luminosity functions of RGB stars in inner spheroid and outer halo clusters have similar slopes, although there is a tendency for core-collapsed clusters to have slightly flatter luminos ity functions than noncollapsed clusters. The distribution of red HB stars on the (K, J-K) CMDs of inner spheroid clusters with [Fe/H] similar to -1.5 is very different from that of clusters with [Fe/H]similar to -2.2, sugges ting that metallicity is the main parameter defining HB content among these objects. The RGB bump is detected in four of the inner spheroid clusters, and this feature is used to compute distances to these objects. Finally, th e specific frequency of globular clusters in the inner Galaxy is discussed in the context of the early evolution of the bulge. Based on the ratio of m etal-poor to metal-rich clusters in the inner Galaxy it is suggested that t he metal-poor clusters formed during an early intense burst of star formati on. It is also demonstrated that if the globular cluster formation efficien cy for the inner Galaxy is similar to that measured in other spheroidal sys tems, then the main body of the bulge could have formed from gas that was c hemically enriched in situ; hence, material from a separate pre-enriched re servoir, such as the disk or outer halo, may not be required to form the bu lge.