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

Abstract

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 Omega 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 cluster members, because this element can only be produced by the main s-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 Omega 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.

A&A, in press

References in corpus (12)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• An abundance analysis of bright giants in the globular cluster NGC 1851
• Improved Laboratory Transition Probabilities for Ce II, Application to the Cerium Abundances of the Sun and Five r-process Rich, Metal-Poor Stars, and Rare Earth Lab Data
• Rubidium-Rich Asymptotic Giant Branch Stars
• s-Process Nucleosynthesis in Advanced Burning Phases of Massive Stars
• Deep FORS1 observations of the double Main Sequence of omega Centauri
• Comparing CN and CH Line Strengths in a Homogeneous Spectroscopic Sample of 8 Galactic Globular Clusters
• Primordial r-process Dispersion in Metal-Poor Globular Clusters
• Heavy elements and chemical enrichment in globular clusters
• O and Na abundance patterns in open clusters of the Galactic disk

Cited by in corpus (29)

• Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• What is a globular cluster? An observational perspective
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• The metallicity spread and the age-metallicity relation of Omega Centauri
• A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)
• Star Formation Histories of Globular Clusters with Multiple Populations. I. ω Cen, M22, and NGC 1851
• NGC 362: another globular cluster with a split red giant branch
• Heavy elements in Globular Clusters: the role of AGB stars
• An aluminium tool for multiple stellar generations in the globular clusters 47 Tuc and M 4
• Detailed Chemical Abundances in NGC 5824: Another Metal-Poor Globular Cluster with Internal Heavy Element Abundance Variations
• Chemical abundances in bright giants of the globular cluster M62 (NGC 6266)
• A critical look at the merger scenario to explain multiple populations and rotation in iron-complex globular clusters
• Metallicity variations in the Type II globular cluster NGC6934
• Nucleosynthesis in helium-enriched asymptotic giant branch models: Implications for Heavy Element Enrichment in Omega Centauri
• R-process-rich stellar streams in the Milky Way
• On the internal pollution mechanisms in the globular cluster NGC 6121 (M4): heavy-element abundances and AGB models
• From the CMD of Omega Centauri and (super-)AGB stellar models to a Galactic plane passage gas purging chemical evolution scenario
• Confirming the intrinsic abundance spread in the globular cluster NGC 6273 (M 19) with calcium triplet spectroscopy
• Rubidium abundances in the globular clusters NGC 6752, NGC 1904 and NGC 104 (47 Tuc)
• A chemical signature from fast-rotating low-metallicity massive stars: ROA 276 in omega Centauri
• Abundance ties: Nephele and the globular cluster population accreted with $\omega$ Cen. Based on APOGEE DR17 and Gaia EDR3
• Stellar population astrophysics (SPA) with the TNG -- The Arcturus Lab
• The Massive M31 Cluster G1: Detailed Chemical Abundances from Integrated Light Spectroscopy
• A new formation model for omega Centauri: the crossroad of astrophysical processes
• The proper motion of sub-populations in Omega Centauri
• High resolution spectroscopy of the relatively hydrogen-poor metal rich giants in the globular cluster Omega Centauri
• Omega Centauri: weak MgH-band in red giants directly trace the helium content