Detailed abundances for A large sample of giant stars in the globular cluster 47 tucanae (NGC 104)

M. J. Cordero, C. A. Pilachowski, C. I. Johnson, I. McDonald, A. A. Zijlstra, J. Simmerer

    Research output: Contribution to journalArticlepeer-review

    Abstract

    47 Tuc is an ideal target to study chemical evolution and globular cluster (GC) formation in massive more metal-rich GCs, as it is the closest massive GC. We present chemical abundances for O, Na, Al, Si, Ca, Ti, Fe, Ni, La, and Eu in 164 red giant branch stars in the massive GC 47 Tuc using spectra obtained with both the Hydra multifiber spectrograph at the Blanco 4 m telescope and the FLAMES multiobject spectrograph at the Very Large Telescope. We find an average [Fe/H] = -0.79 ± 0.09 dex, consistent with literature values, as well as overabundances of alpha-elements ([α/Fe] ∼ 0.3 dex). The n-capture process elements indicate that 47 Tuc is r process-dominated ([Eu/La] = +0.24), and the light elements O, Na, and Al exhibit star-to-star variations. The Na-O anticorrelation, a signature typically seen in Galactic GCs, is present in 47 Tuc, and extends to include a small number of stars with [O/Fe] ∼ -0.5. Additionally, the [O/Na] ratios of our sample reveal that the cluster stars can be separated into three distinct populations. A Kolmogorov-Smirnov test demonstrates that the O-poor/Na-rich stars are more centrally concentrated than the O-rich/Na-poor stars. The observed number and radial distribution of 47 Tuc's stellar populations, as distinguished by their light element composition, agrees closely with the results obtained from photometric data. We do not find evidence supporting a strong Na-Al correlation in 47 Tuc, which is consistent with current models of asymptotic giant branch nucleosynthesis yields. © 2014. The American Astronomical Society. All rights reserved.
    Original languageEnglish
    Article number94
    JournalAstrophysical Journal
    Volume780
    Issue number1
    Early online date13 Dec 2013
    DOIs
    Publication statusPublished - 1 Jan 2014

    Keywords

    • globular clusters: individual (47 Tucanae)
    • stars: abundances
    • stars: Population II

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