Page History
Project duration: 1 year. Potential to grow into a thesis project (see below)
PI: Annalisa Calamida (INS/WFC3), RW303, 667 218 6428
NGC2808 is the second most massive Galactic globular cluster
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and a very peculiar object. HST photometric studies
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showed that the cluster main-sequence splits in a blue, an intermediate
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and a red sequence (see Fig. 1) and that stars on the intermediate and blue main
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sequences are more centrally concentrated compared to stars on the red main-sequence.
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It was suggested that NGC2808 experienced different episodes of star
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formation with a significant helium enrichment, with the bluest main-sequence
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being the most enhanced. However, high-resolution spectroscopic
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measurements of red-giant stars indicate that, while expected in the case of
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different star formation episodes, no spread in iron content is present in NGC2808.
A consensus on the origin of the different stellar populations
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in NGC2808 has not been reached yet. Previous findings are based on data
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for a few small fields centered on the cluster (HST) or for a field of
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view covering about half the tidal radius (ground). There is now the need
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for deep photometry covering the entire cluster (tidal radius rt ~ 16 arcmin)
with the accuracy necessary to enable the identification of the
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different main sequences. This photometric catalog would allow the homogenous
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study of the multiple populations in NGC2808 and possibly a clear understanding
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of the origin and evolution of this peculiar globular cluster.
We have
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proprietary wide-field DECam (mounted on the 4m-Blanco telescope, NOAO)
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observations that cover the entire extent of NGC2808 and so will enable
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us to characterize the spatial distribution of the main-sequence (and red-giant)
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stars from the core to the tidal radius and obtain a clear picture of the
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evolutionary history of the cluster.
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The observations will then be compared to numerical simulations
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performed by our collaborators to characterize the formation and
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evolutionary history of this complex cluster.
