The globular cluster NGC 6528 the ferrous side of the Galactic Bulge

E. P. Lagioia, A. P. Milone, G. Bono, P. B. Stetson, A. Aparicio, R. Buonanno, A. Calamida, M. Dall'Ora, I. Ferraro, R. Gilmozzi, G. Iannicola, N. Matsunaga, M. Monelli, P. G. Prada Moroni, A. Walker

Published 2014-02-05Version 1

We present new and accurate optical photometry of the Bulge globular cluster NGC 6528. The images were collected with ACS at HST and together with WFC3 (UVIS, IR) allowed us to measure the proper motion to separate cluster and field stars. We adopted two empirical calibrators and we found that NGC 6528 is coeval with and more metal-rich than 47 Tuc. Moreover, it appears older and more metal-poor than the super-metal-rich old open cluster NGC 6791. We also performed a preliminary analysis of field stellar populations located around NGC 6528 and NGC 6522 by using ground-based near-infrared photometry collected with SOFI at NTT. The comparison of evolved stellar components (red giant branch, red horizontal branch, red clump stars) indicates that they share similar properties in this region of the Baade's Window.