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Project duration: 1 year. Potential to grow into a thesis project (see below)
PI: Annalisa Dr. Annalisa Calamida (INS/WFC3), Office: RW303, Email: calamida@stsci.edu, Phone: 667 218 6428
Galactic globular clusters (GGCs) have long been considered the most simple stellar populations, with their stars located at the same distance, with typically the same extinction, and the same bona fide age and chemical composition. However, during the last two decades, high-resolution spectroscopic studies have shown that most GGCs display a large spread of light elements and anti-correlations. This evidence suggests the presence of more than one generation of stars in these systems, with the younger generation born from a stellar medium enriched by the material ejected by the previous one.
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A consensus on the origin of the different stellar populations in NGC2808 has not been reached yet. Previous findings are based on data for a few small fields centered on the cluster (HST) or for a field of view covering about half the tidal radius (ground). There is now the need for deep photometry covering the entire cluster (tidal radius rt rt ~ 16 arcmin)
with the accuracy necessary to enable the identification of the different main sequences. This photometric catalog would allow the homogenous study of the multiple populations in NGC2808 and possibly a clear understanding of the origin and evolution of this peculiar globular cluster.
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Fig. 2: DECam g-i vs u-r vs r color-color-magnitude diagram of Omega Cen member (multiple color dots) and field stars (gray dots) seen from the front (left top panel) and the back (rightbottom). This approach can be applied to separate field and cluster stars thanks to the opportunity to use the u filter, since this band allows a better sensitivity to both effective temperature and metallicity. We will apply this method to separate cluster and field stars in NGC2808. This figure is taken from Calamida et al. (2017, AJ, 153, 175).
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