The VMC Survey. XI. Radial Stellar Population Gradients in the Galactic Globular Cluster 47 Tucanae
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2014
- DOI:
- 10.1088/0004-637X/790/1/35
- arXiv:
- arXiv:1406.1259
- Bibcode:
- 2014ApJ...790...35L
- Keywords:
-
- globular clusters: individual: 47 Tuc NGC 104;
- Hertzsprung-Russell and C-M diagrams;
- infrared: stars;
- stars: Population II;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 40 pages, 20 figures, accepted for publication in ApJ