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Symposium 241

Abstract details

Extragalactic globular clusters: unraveling galaxy formation and constraining stellar evolution theories
A.J. Cenarro, M.A. Beasley, J.P. Brodie & J. Strader

We present high-quality, Keck spectroscopic data of globular clusters (GCs) in the E0 NGC1407. Ages, metallicities and element abundance ratios for the GCs have been derived on the basis of their Lick/IDS indices and recent single stellar population model predictions. Overall, most GCs in NGC1407 turn out to be old, follow a tight metallicity sequence reaching values above solar, and pose mean [$\alpha$/Fe] ratios of $\sim 0.2 - 0.3$\,dex. In spite of three GCs are derived to be young (3 -- 4\,Gyr), we have proven them to be consistent with old GCs hosting blue horizontal branches. Concerning chemical abundances, we report, for the first time, evidence for the existence of two chemically-distinct subpopulations of metal-rich (MR) GCs with well different [Mg/Fe] and [C/Fe] ratios. Different star-formation time-scales are proposed to explain the correlation between Mg and C abundances. Whilst CN overabundances are evident all over the GC metallicity range, the behavior of C and N in metal-poor (MP) GCs clearly deviates from the one in MR GCs. This may be interpreted as a consequence of the increasing importance of the CNO cycle with the increasing metallicity.

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