Chemical tagging of three distinct populations of red giants in the globular cluster NGC6752

E. Carretta*, A. Bragaglia, R. G. Gratton, S. Lucatello, V. D'Orazi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

56 Citations (Scopus)


We present aluminum, magnesium, and silicon abundances in the metal-poor globular cluster NGC6752 for a sample of more than 130 red giants with homogeneous oxygen and sodium abundances. We find that [Al/Fe] shows a spread of about 1.4 dex among giants in NGC6752 and is anticorrelated with [Mg/Fe] and [O/Fe] and correlated with [Na/Fe] and [Si/Fe]. These relations are not continuous in nature, but the distribution of stars is clearly clustered around three distinct Al values, low, intermediate, and high. These three groups nicely correspond to the three distinct sequences previously detected using Strömgren photometry along the red giant branch. These two independent findings strongly indicate the existence of three distinct stellar populations in NGC6752. Comparing the abundances of O and Mg, we find that the population with intermediate chemical abundances cannot originate from material with the same composition of the most O- and Mg-poor population, diluted by material with that of the most O- and Mg-rich one. This calls for different polluters.

Original languageEnglish
Article numberL14
Pages (from-to)1-5
Number of pages5
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - 1 May 2012

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