The outer-halo globular cluster NGC 6229 III. Deep CCD photometry

Deep BV photometry for a large field covering the outer-halo globular clust er NGC 6229 is presented. For the first time, a colour-magnitude diagram (C MD) reaching below the main sequence turnoff has been obtained for this clu ster. Previous results regarding the overall morphology of the horizontal a nd giant branches are confirmed. In addition, nine possible extreme horizon tal-branch stars have been identified in our deep images, as well as thirty -three candidate blue stragglers. We also find the latter to be more centra lly concentrated than subgiant branch stars covering the same range in V ma gnitude. A comparison of the cluster CMD with the M 5 (NGC 5904) ridgeline from Sand quist et al. (1996) reveals that: i) NGC 6229 and M5 have essentially identical metallicities; ii) NGC 6229 and M5 have the same ages within the errors in spite of their different horizontal-branch morphologies.