THE VMC SURVEY. XI. RADIAL STELLAR POPULATION GRADIENTS IN THE GALACTIC GLOBULAR CLUSTER 47 TUCANAE

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.

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, Ks 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.

Citation

Li, C., de Grijs, R., Deng, L., Rubele, S., Wang, C., Bekki, K., Cioni, M.-R. L., Clementini, G., Emerson, J., For, B.-Q., Girardi, L., Groenewegen, M. A. T., Guandalini, R., Gullieuszik, M., Marconi, M., Piatti, A. E., Ripepi, V., & van Loon, J. T. (in press). THE VMC SURVEY. XI. RADIAL STELLAR POPULATION GRADIENTS IN THE GALACTIC GLOBULAR CLUSTER 47 TUCANAE. Astrophysical Journal, 790(1), 35. https://doi.org/10.1088/0004-637x/790/1/35

• Journal Article Type: Article
• Acceptance Date: May 28, 2014
• Online Publication Date: Jun 30, 2014
• Deposit Date: Jun 16, 2023
• Journal: The Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 790
• Issue: 1
• Pages: 35
• DOI: https://doi.org/10.1088/0004-637x/790/1/35
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://keele-repository.worktribe.com/output/473327