Chemical composition of stellar populations in Omega Centauri

TL;DR

This study analyzes the chemical abundances of over 200 red giant stars in Omega Centauri, revealing multiple stellar populations with distinct metallicities and chemical patterns, including Na-O anticorrelations and metallicity variations.

Contribution

It provides detailed chemical abundance measurements for a large sample of stars in Omega Centauri, confirming multiple populations and chemical trends not previously characterized in detail.

Findings

Omega Centauri exhibits large star-to-star metallicity variations (~1.4 dex).

At least five stellar populations with different [Fe/H] are identified.

Na-O anticorrelation is present in metal-poor and intermediate populations, but not in the most metal-rich ones.

Abstract

We derive abundances of Fe, Na, O, and s-elements from GIRAFFE@VLT spectra for more than 200 red giant stars in the Milky Way satellite Omega Centauri. Our preliminary results are that: (i) we confirm that Omega Centauri exibiths large star-to-star metallicity variations ($\sim$ 1.4 dex); (ii) the metallicity distribution reveals the presence of at least five stellar populations with different [Fe/H]; (iii) a clear Na-O anticorrelation is clearly observed for the metal-poor and metal-intermediate populations while apparently the anticorrelation disappears for the most metal-rich populations. Interestingly the Na level grows with iron.