Abundance analysis of a sample of evolved stars in the outskirts of Omega Centauri

Abstract

The globular cluster $\omega$ Centauri (NGC 5139) is a puzzling stellar system harboring several distinct stellar populations whose origin still represents a unique astrophysical challenge. Current scenarios range from primordial chemical inhomogeneities in the mother cloud to merging of different sub-units and/or subsequent generations of enriched stars - with a variety of different pollution sources- within the same potential well. In this paper we study the chemical abundance pattern in the outskirts of Omega Centauri, half-way to the tidal radius (covering the range of 20-30 arcmin from the cluster center), and compare it with chemical trends in the inner cluster regions, in an attempt to explore whether the same population mix and chemical compositions trends routinely found in the more central regions is also present in the cluster periphery.We extract abundances of many elements from FLAMES/UVES spectra of 48 RGB stars using the equivalent width method and then analyze the metallicity distribution function and abundance ratios of the observed stars. We find, within the uncertainties of small number statistics and slightly different evolutionary phases, that the population mix in the outer regions cannot be distinguished from the more central regions, although it is clear that more data are necessary to obtain a firmer description of the situation. From the abundance analysis, we did not find obvious radial gradients in any of the measured elements.

22 pages, 8 eps figures, in press in New Astronomy

References in corpus (8)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Spectroscopic and Photometric evidence of two stellar populations in the Galactic Globular Cluster NGC6121 (M4)
• Origin of multiple stellar populations in globular clusters and their helium enrichment
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• The origin of globular cluster systems from cosmological simulations
• Evidence of tidal debris from Omega Cen in the Kapteyn Group
• The chemical evolution of Omega Centauri's progenitor system
• Using globular clusters to test gravity in the weak acceleration regime

Cited by in corpus (7)

• Chemical Abundances for 855 Giants in the Globular Cluster Omega Centauri (NGC 5139)
• The origin and orbit of the old, metal-rich, open cluster NGC 6791: Insights from kinematics
• The subgiant branch of omega Cen seen through high-resolution spectroscopy. I. The first stellar generation in omega Centauri?
• Excess of Ca (and Sc) produced in globular cluster multiple populations: a first census in 77 Galactic globular clusters
• Spectral matching for abundances and clustering analysis of stars on the giant branches of ω Centauri
• Spectral matching for abundances of 848 stars of the giant branches of the globular cluster ω Centauri
• Intrinsic Metallicity Variation in the Intermediate Mass Type II Globular Cluster NGC 1261