oMEGACat III. Multi-band photometry and metallicities reveal spatially well-mixed populations within $\omega$ Centauri's half-light radius

TL;DR

This study uses spectroscopic and photometric data to analyze the metallicity distribution and spatial mixing of populations within $$ Centauri, finding no metallicity gradient and well-mixed sub-populations within its half-light radius.

Contribution

It provides detailed metallicity and spatial distribution analysis of $$ Centauri's populations using new spectroscopic and photometric data, revealing well-mixed populations without a metallicity gradient.

Findings

Median metallicity of -1.614 dex with a 1.37 dex spread.

No metallicity gradient within the half-light radius.

Populations are spatially well mixed.

Abstract

$\omega$ Centauri, the most massive globular cluster in the Milky Way, has long been suspected to be the stripped nucleus of a dwarf galaxy that fell into the Galaxy a long time ago. There is considerable evidence for this scenario including a large spread in metallicity and an unusually large number of distinct sub-populations seen in photometric studies. In this work, we use new MUSE spectroscopic and HST photometric catalogs to investigate the underlying metallicity distributions as well as the spatial variations of the populations within the cluster up to its half-light radius. Based on 11,050 member stars, the [M/H] distribution has a median of $ (-1.614 \pm 0.003)$ dex and a large spread of $\sim$ 1.37 dex reaching from $ -0.67$ dex to $ -2.04$ dex for 99.7 % of the stars. In addition, we show the chromosome map of the cluster, which separates the red giant branch stars into different sub-populations, and analyze the sub-populations of the metal-poorest component. Finally, we do not find any metallicity gradient within the half-light radius, and the different sub-populations are well mixed.