The Age of the Inner Halo Globular Cluster NGC 6652

HST (V,I) photometry has been obtained for the inner halo globular clusterNGC 6652. The photometry reaches approximately 4 mag below the turn-off andincludes a well populated horizontal branch. This cluster is located close tothe Galactic center at a galactocentric distance of approximately 2.0 kpc witha reddening of E(V-I) = 0.15 +/- 0.02 and has a metallicity of [Fe/H]approximately -0.85. Based upon Delta(V) between the point on the sub-giantbranch which is 0.05 mag redder than the turn-off and the horizontal branch,NGC 6652 is 11.7 +/- 1.6 Gyr old. Using this same Delta(V), precisedifferential ages for 47 Tuc (a thick disk globular), M107 and NGC 1851 (bothhalo clusters) were obtained. NGC 6652 appears to be the same age as 47 Tuc andNGC 1851 (within +/- 1.2 Gyr), while there is a slight suggestion that M107 isolder than NGC 6652 by 2.3 +/- 1.5 Gyr. As this is a less than 2-sigma result,this issue needs to be investigated further before a definitive statementregarding the relative age of M107 and NGC 6652 may be made.Comment: accepted for publication in the Astronomical Journal, December 2000 issu