The VMC Survey. XI. Radial Stellar Population Gradients in the Galactic Globular Cluster 47 Tucanae
| Autor: | Li, Chengyuan, de Grijs, Richard, 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, van Loon, Jacco Th. |
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| Rok vydání: | 2014 |
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| Druh dokumentu: | Working Paper |
| DOI: | 10.1088/0004-637X/790/1/35 |
| Popis: | 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. Comment: 40 pages, 20 figures, accepted for publication in ApJ |
| Databáze: | arXiv |
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