Abundances from integrated spectra of 47 Tucanae (NGC 104)

Abstract

47 Tucanae is among the most studied and observed globular clusters, given its proximity. The aim of this work is to study in detail the integrated spectrum of 47 Tucanae, as a template, in order to have a list of reliable lines that are validated for a moderate spectral resolution case. The spectrum of 47 Tucanae is reproduced by computing synthetic spectra, taking into account individual element abundances. The results are compared with other methods. We reproduce the integrated spectrum in the range 4500–9000 Å and derive abundances from individual lines of Na, Mg, Al, Si, Ca, Ti, Ba, and Eu. We report a list of lines that are suitable for abundance derivation. Adopting these abundances, we are able to fit the well-known triplets of Mg I and Ca II. Finally, the effect of multiple stellar populations through enhanced Na abundances are tested. Element abundances derived are compatible with previous literature abundances, from different methods. The method applied here to build integrated synthetic spectra can be used to derive abundances from observed integrated spectra of distant and faint clusters, that are usually observed at low or moderate spectral resolution.