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arXiv · 1609.02152

Ultra-deep GEMINI near-infrared observations of the bulge globular cluster NGC 6624

S. Saracino·E. Dalessandro·F. R. Ferraro·D. Geisler·F. Mauro·B. Lanzoni·L. Origlia·P. Miocchi·R. E. Cohen·S. Villanova·C. Moni Bidin
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Abstract

We used ultra-deep $J$ and $K_s$ images secured with the near-infrared GSAOI camera assisted by the multi-conjugate adaptive optics system GeMS at the GEMINI South Telescope in Chile, to obtain a ($K_s$, $J-K_s$) color-magnitude diagram (CMD) for the bulge globular cluster NGC 6624. We obtained the deepest and most accurate near-infrared CMD from the ground for this cluster, by reaching $K_s$ $\sim$ 21.5, approximately 8 magnitudes below the horizontal branch level. The entire extension of the Main Sequence (MS) is nicely sampled and at $K_s$ $\sim$ 20 we detected the so-called MS "knee" in a purely near-infrared CMD. By taking advantage of the exquisite quality of the data, we estimated the absolute age of NGC 6624 ($t_{age}$ = 12.0 $\pm$ 0.5 Gyr), which turns out to be in good agreement with previous studies in the literature. We also analyzed the luminosity and mass functions of MS stars down to M $\sim$ 0.45 M$_{\odot}$ finding evidence of a significant increase of low-mass stars at increasing distances from the cluster center. This is a clear signature of mass segregation, confirming that NGC 6624 is in an advanced stage of dynamical evolution.

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S. Saracino, E. Dalessandro, F. R. Ferraro, D. Geisler, F. Mauro, B. Lanzoni, L. Origlia, P. Miocchi, R. E. Cohen, S. Villanova, C. Moni Bidin. 2016-09-07. Ultra-deep GEMINI near-infrared observations of the bulge globular cluster NGC 6624. https://doi.org/10.3847/0004-637x%2F832%2F1%2F48

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