1. THE VMC SURVEY. XI. RADIAL STELLAR POPULATION GRADIENTS IN THE GALACTIC GLOBULAR CLUSTER 47 TUCANAE.
- Author
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Li, Chengyuan, Grijs, Richard de, Deng, Licai, Rubele, Stefano, Wang, Chuchu, Bekki, Kenji, Cioni, Maria-Rosa L., Clementini, Gisella, Emerson, Jim, For, Bi-Qing, Girardi, Leo, Groenewegen, Martin A. T., Guandalini, Roald, Gullieuszik, Marco, Marconi, Marcella, Piatti, Andrés E., Ripepi, Vincenzo, and Loon, Jacco Th. van
- Subjects
GLOBULAR clusters ,GALAXIES ,LARGE astronomical telescopes ,STELLAR activity ,HELIUM - Abstract
We present a deep near-infrared color-magnitude diagram of the Galactic globular cluster 47 Tucanae, obtained with the Visible and Infrared Survey Telescope for Astronomy (VISTA) as part of the VISTA near-infrared Y, J, K
s survey of the Magellanic System (VMC). The cluster stars comprising both the subgiant and red giant branches exhibit apparent, continuous variations in color-magnitude space as a function of radius. Subgiant branch stars at larger radii are systematically brighter than their counterparts closer to the cluster core; similarly, red-giant-branch stars in the cluster's periphery are bluer than their more centrally located cousins. The observations can very well be described by adopting an age spread of ∼0.5 Gyr as well as radial gradients in both the cluster's helium abundance (Y) and metallicity (Z), which change gradually from (Y = 0.28, Z = 0.005) in the cluster core to (Y = 0.25, Z = 0.003) in its periphery. We conclude that the cluster's inner regions host a significant fraction of second-generation stars, which decreases with increasing radius; the stellar population in the 47 Tuc periphery is well approximated by a simple stellar population. [ABSTRACT FROM AUTHOR]- Published
- 2014
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