Chemical enrichment mechanisms in Omega Centauri: clues from neutron-capture elements

V. D'Orazi*, R. Gratton, E. Pancino, A. Bragaglia, E. Carretta, S. Lucatello, C. Sneden

*Corresponding author for this work

    Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution


    In the complex picture of multiple stellar populations in globular clusters (GCs), a special role is played by NGC 5139 (omega Centauri). At variance with the majority of GCs, omega Cen exhibits significant star-to-star variations in metallicity and in relative neutron-capture element abundance ratios with respect to Fe, along with split evolutionary sequences as revealed from colour-magnitude diagrams. Combining information from photometry and spectroscopy, several studies suggested that an age spread of several Gyr has to be invoked to explain (at least partially) some of the observed features. However, a comprehensive understanding of the formation, evolution and chemical enrichment processes is still not at hand. Relatively metal-rich a Cen stars display neutron-capture abundance distributions dominated by contributions from the s-process, but it is not clear what roles have been played by the so-called main and weak s-process components in generating these abundances. To gain better insight into this question we derived lead (Pb) abundances for several omega Cen cluster members, because this element can only be produced by the mains-process. We analysed high-resolution UVES@VLT spectra of a sample of twelve red-giant branch stars, deriving abundances of Pb and also of Y, Zr, La, Ce, Eu, and the C+N+O sum. Spectral synthesis was applied to all features, taking into account isotopic shifts and/or hyperfine structure as needed. We measured for the first time the Pb content in w Cen, discovering a clear hint for a Pb production occurring at [Fe/H]> -1.7 dex. Our data suggest that the role of the weak component in the production of s-process elements is negligible. Moreover, evidence gathered from the abundances of other elements indicates that the main component occurring in this GC is peculiar and shifted towards higher mass polluters than the standard one.

    Original languageEnglish
    Title of host publicationGalactic archaeology
    Subtitle of host publicationnear-field cosmology and the formation of the milky way
    EditorsWako Aoki, Miho Ishigaki, Takuma Suda, Takuji Tsujimoto, Nobou Arimoto
    Place of PublicationSan Francisco
    Number of pages2
    ISBN (Electronic)9781583817995
    ISBN (Print)9781583817988
    Publication statusPublished - 2012
    EventConference on the Galactic Archaeology - Near-Field Cosmology and the Formation of the Milky Way - Shuzenji, Japan
    Duration: 1 Nov 20114 Nov 2011

    Publication series

    NameAstronomical Society of the Pacific Conference Series


    ConferenceConference on the Galactic Archaeology - Near-Field Cosmology and the Formation of the Milky Way


    Dive into the research topics of 'Chemical enrichment mechanisms in Omega Centauri: clues from neutron-capture elements'. Together they form a unique fingerprint.

    Cite this