Discovery of an accreted stellar system within the globular cluster omega Centauri

Abstract

Recent wide-field photometric surveys (Lee et al.; Pancino et al.) have shown the existence of a previously unknown metal-rich ([Fe/H] -0.6) stellar population in the galactic globular cluster omega Centauri. The discovery of this new component, which comprises only a small percentage (~5%) of the entire cluster population, has added a new piece to the already puzzling picture of the star formation and chemical evolution of this stellar system. In this Letter we show that stars belonging to the newly discovered metal-rich population have a coherent bulk motion with respect to the other cluster stars, thus demonstrating that they formed in an independent self-gravitating stellar system. This is the first clear-cut evidence that extreme metal-rich stars were part of a small stellar system (a satellite of omega Centauri?) that has been accreted by the main body of the cluster. In this case, we are witnessing an in vivo example of hierarchical merging on the sub-galactic scale.

11 pages, 3 figures, accepted for publication in ApJ Letters

Cited by in corpus (37)

• Omega Centauri: The Population Puzzle Goes Deeper
• Formation of omega Centauri from an ancient nucleated dwarf galaxy in the young Galactic disc
• The dynamical distance and intrinsic structure of the globular cluster omega Centauri
• New Limits on an Intermediate Mass Black Hole in Omega Centauri: I. Hubble Space Telescope Photometry and Proper Motions
• The Draco and Ursa Minor dwarf spheroidals. A comparative study
• The State-of-the-Art HST Astro-Photometric Analysis of the core of $\omega$ Centauri. I. The Catalog
• Secondary star formation within massive star clusters: Origin of multiple stellar populations in globular clusters
• Metallicities, relative ages and kinematics of stellar populations in omega Centauri
• Radial distribution of the multiple stellar populations in omega Centauri
• Deep FORS1 observations of the double Main Sequence of omega Centauri
• The HST large programme on $\omega$ Centauri - II. internal kinematics
• Na-O anticorrelation and HB. IX. Kinematics of the program clusters. A link between systemic rotation and HB morphology?
• Discovery of an anomalous Sub Giant Branch in the Color Magnitude Diagram of omega Centauri
• Testing intermediate-age stellar evolution models with VLT photometry of LMC clusters. III. Padova results
• A near-infrared spectroscopic screening of the red giant populations in omega Centauri
• Rotation and multiple stellar population in globular clusters
• The Rotation of Sub-Populations in omega Centauri
• CCD Photometry of the Globular Cluster omega Centauri. II. Stellar Populations and Age-Metallicity Relation
• Fe and Al Abundances for 180 Red Giants in the Globular Cluster Omega Centauri (NGC 5139)
• An XMM-Newton observation of the globular cluster Omega Centauri
• The Age and Metallicity Relation of Omega Centauri
• Evolution of second generation stars in stellar disks of globular and nuclear clusters: Omega Centauri as a test case
• The multiple stellar population in omega Centauri: spatial distribution and structural properties
• A spectral atlas of post-main-sequence stars in omega Centauri: kinematics, evolution, enrichment and interstellar medium
• The chemical evolution of Omega Centauri's progenitor system
• New SX Phoenicis Stars in the Globular Cluster M53
• The not so simple globular cluster $\omega$ Cen. I. Spatial distribution of the multiple stellar populations
• IR photometric properties of Red Giants in omega Cen
• Star Formation History of Omega Centauri Imprinted in Elemental Abundance Patterns
• The not so simple stellar system Omega Cen. II. Evidence in support of a merging scenario
• AAOmega Observations of 47 Tucanae: Evidence for a Past Merger?
• Surface pollution of main-sequence stars through encounters with AGB ejecta in omega Centauri
• On the anomalous red giant branch of the globular cluster Omega Cen
• Stellar populations in $\omega$ Centauri: a multivariate analysis
• A new formation model for omega Centauri: the crossroad of astrophysical processes
• The proper motion of sub-populations in Omega Centauri
• Kinematics of metallicity populations in Omega Centauri using Gaia Focused Product Release and Hubble Space Telescope