Abstract
| Alvarez Garay |
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| The extreme MgAl chain as a probe for the Multiple Populations in Omega Centauri |
| Nowadays we know that Globular Clusters (GCs) are formed by multiple populations (MPs) with different light element abundances (C, N, O, Na, Mg, Al, Si, K) within the cluster stars. The observed chemical differences are structured in well-defined patterns, such as the Na-O and Mg-Al anti-correlations. The evidence is interpreted as the signature of a self-enrichment process within the cluster, where a second population of stars was formed from material processed in the first population (or polluter) stars through the hot CNO cycle and its secondary NeNa and MgAl chains. To disentangle among the polluters proposed in the literature, the study of (anti-)correlations generated by the MgAl chain is of paramount relevance since not all the candidate polluters are able to activate this chain. In this sense, ω Centauri represents an ideal laboratory to study these chemical anomalies. This GC-like system is probably the nuclear star cluster of a disrupted dwarf galaxy and it exhibits magnified all the chemical anomalies usually observed in normal GCs. In this talk, I present Mg, Al, and Si abundances for 439 ω Centauri stars, observed with the high-resolution spectrograph FLAMES@VLT. We observed the presence of discrete Mg-Al, Mg-Si, and Si-Al (anti-)correlations in all the stars with [Fe/H]<-1.3, while at higher metallicities their presence is weak or even absent: these findings can help to put more constraints on the nature of polluters responsible for the formation of Mps in GCs. |