On the Kinematic Separation of Field and Cluster Stars across the Bulge Globular NGC 6528

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

The Astrophysical Journal, Volume 782, Issue 1, article id. 50, 11 pp. (2014).

Advertised on:
2
2014
Number of authors
15
IAC number of authors
3
Citations
24
Refereed citations
21
Description
We present deep and precise multi-band photometry of the Galactic bulge globular cluster NGC 6528. The current data set includes optical and near-infrared images collected with ACS/WFC, WFC3/UVIS, and WFC3/IR on board the Hubble Space Telescope. The images cover a time interval of almost 10 yr, and we have been able to carry out a proper-motion separation between cluster and field stars. We performed a detailed comparison in the m F814W, m F606W – m F814W color-magnitude diagram with two empirical calibrators observed in the same bands. 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 open cluster NGC 6791. The current evidence is supported by several diagnostics (red horizontal branch, red giant branch bump, shape of the sub-giant branch, slope of the main sequence) that are minimally affected by uncertainties in reddening and distance. We fit the optical observations with theoretical isochrones based on a scaled-solar chemical mixture and found an age of 11 ± 1 Gyr and an iron abundance slightly above solar ([Fe/H] = +0.20). The iron abundance and the old cluster age further support the recent spectroscopic findings suggesting a rapid chemical enrichment of the Galactic bulge.
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NGC 2808 Globular Cluster
Milky Way and Nearby Galaxies
The general aim of the project is to research the structure, evolutionary history and formation of galaxies through the study of their resolved stellar populations, both from photometry and spectroscopy. The group research concentrates in the most nearby objects, namely the Local Group galaxies including the Milky Way and M33 under the hypothesis
Martín
López Corredoira