Abundance analysis of a sample of evolved stars in the outskirts of ω Centauri
Authors
Sandro Villanova (1), Giovanni Carraro (2), Riccardo Scarpa (3), and Gianni Marconi (2)
Affiliation
(1) Universidad de Concepcion
(2) ESO-Chile
(3) IAC-GTC
Accepted by
New Astronomy
Contact
URL
Links
Abstract
The globular cluster ω 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 ω 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 pha
ses,
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.