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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 and  a very peculiar object. HST photometric studies showed 
that the cluster main-sequence splits in a blue, an intermediate and 
a red sequence and that stars on the intermediate and blue main sequences 
are more centrally concentrated compared to stars on the red main-sequence.
It was suggested that NGC2808 experienced different episodes of star formation 
with a significant helium enrichment, with the bluest main-sequence being 
the most enhanced. However, high-resolution spectroscopic measurements 
of red-giant stars indicate that, while expected in the case of different 
star formation episodes, no spread in iron content is present in NGC2808. 

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 ~ 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.

We have propietary wide-field DECam (mounted on the 4m-Blanco telescope, NOAO) 
observations that cover the entire extent of NGC2808 and so will enable us 
to characterize the spatial distribution of the main-sequence (and red-giant) 
stars from the core to the tidal radius and obtain a clear picture of the
evolutionary history of the cluster. 
The observations will then be compared to numerical simulations performed 
by our collaborators to characterize the formation and evolutionary 
history of this complex cluster.