The Most Metal-poor Stars in Omega Centauri (NGC 5139)

Abstract

The most massive and complex globular clusters in the Galaxy are thought to have originated as the nuclear cores of now tidally disrupted dwarf galaxies, but the connection between globular clusters and dwarf galaxies is tenuous with the M54/Sagittarius system representing the only unambiguous link. The globular cluster Omega Centauri (w Cen) is more massive and chemically diverse than M 54, and is thought to have been the nuclear star cluster of either the Sequoia or Gaia-Enceladus galaxy. Local Group dwarf galaxies with masses equivalent to these systems often host significant populations of very metal-poor stars ([Fe/H] < -2.5), and one might expect to find such objects in w Cen. Using high resolution spectra from Magellan-M2FS, we detected 11 stars in a targeted sample of 395 that have [Fe/H] ranging from -2.30 to -2.52. These are the most metal-poor stars discovered in the cluster, and are 5x more metal-poor than w Cen's dominant population. However, these stars are not so metal-poor as to be unambiguously linked to a dwarf galaxy origin. The cluster's metal-poor tail appears to contain two populations near [Fe/H] ~ -2.1 and -2.4, which are very centrally concentrated but do not exhibit any peculiar kinematic signatures. Several possible origins for these stars are discussed.

arXiv commentAJ In press; 29 pages, 5 Figures

References in corpus (79)

• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies
• Intrinsic iron spread and a new metallicity scale for Globular Clusters
• RVSAO 2.0: Digital Redshifts and Radial Velocities
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• Detecting Bimodality in Astronomical Datasets
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• Origin of the system of globular clusters in the Milky Way
• The hierarchical formation of a stellar cluster
• SkyMapper Southern Survey: First Data Release (DR1)
• Multiple Stellar Populations in the Globular Cluster omega Centauri as Tracers of a Merger Event
• Formation of omega Centauri from an ancient nucleated dwarf galaxy in the young Galactic disc
• NLTE line formation of Fe for late-type stars. I. Standard stars with 1D and <3D> model atmospheres
• NLTE line formation of Fe in late-type stars II: 1D spectroscopic stellar parameters
• Chemical Abundances for 855 Giants in the Globular Cluster Omega Centauri (NGC 5139)
• Modeling the Metallicity Distribution of Globular Clusters
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. III. Metallicity Distributions of Milky Way Dwarf Satellite Galaxies
• The DART imaging and CaT survey of the Fornax Dwarf Spheroidal Galaxy
• The dynamical distance and intrinsic structure of the globular cluster omega Centauri
• The properties of Galactic globular cluster sub-systems
• Population Gradients in Local Group Dwarf Spheroidals
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• Detailed abundances of a large sample of giant stars in M 54 and in the Sagittarius nucleus
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• The multiplicity of the subgiant branch of Omega Centauri: Evidence for prolonged star formation
• New evidence for the complex struscture of the RGB of Omega Cen
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Multi-Element Abundance Measurements from Medium-Resolution Spectra. I. The Sculptor Dwarf Spheroidal Galaxy
• Sodium-oxygen anticorrelation and neutron capture elements in Omega Centauri stellar populations
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• The Abundance Spread Among Giants and Subgiants in the Globular Cluster Omega Centauri
• The Chemical Enrichment History of the Small Magellanic Cloud and Its Gradients
• Globular cluster systems in nearby dwarf galaxies - II. Nuclear star clusters and their relation to massive Galactic globular clusters
• Abundances for a large sample of red giants in NGC 1851: hints for a merger of two clusters?
• New HST WFC3/UVIS observations augment the stellar-population complexity of omega Centauri
• Ceci n'est pas a globular cluster: the metallicity distribution of the stellar system Terzan 5
• The Comparative Chemical Evolution of an Isolated Dwarf Galaxy: A VLT and Keck Spectroscopic Survey of WLM
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• The metallicity spread and the age-metallicity relation of Omega Centauri
• SD 1313-0019 -- Another second-generation star with [Fe/H] = -5.0, observed with the Magellan Telescope
• The Terzan 5 puzzle: discovery of a third, metal-poor component
• A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)
• Exploring Halo Substructure with Giant Stars: Substructure in the Local Halo as Seen in the Grid Giant Star Survey Including Extended Tidal Debris from Omega Centauri
• Discovery of Strongly Inverted Metallicity Gradients in Dwarf Galaxies at $z$$\sim$2
• The State-of-the-Art HST Astro-Photometric Analysis of the core of ωCentauri. III. The Main Sequence's Multiple Populations Galore
• CCD Photometry of the Globular Cluster omega Centauri. II. Stellar Populations and Age-Metallicity Relation
• The non-peculiar velocity dispersion profile of the stellar system omega Centauri
• Prolate rotation and metallicity gradient in the transforming dwarf galaxy Phoenix
• Fe and Al Abundances for 180 Red Giants in the Globular Cluster Omega Centauri (NGC 5139)
• An old, metal-poor globular cluster in Sextans A and the metallicity floor of globular cluster systems
• Stromgren photometry of Galactic Globular Clusters. II Metallicity distribution of red giants in Omega Centauri
• AGB Sodium Abundances in the Globular Cluster 47 Tucanae (NGC 104)
• Mergers of Globular Clusters
• Insights from the Outskirts: Chemical and Dynamical Properties in the outer Parts of the Fornax Dwarf Spheroidal Galaxy
• Radial velocities in the globular cluster omega Centauri
• Reddening distribution across the center of the globular cluster Omega Centauri
• Mass estimates from stellar proper motions: The mass of $\omega$ Centauri
• A spectral atlas of post-main-sequence stars in omega Centauri: kinematics, evolution, enrichment and interstellar medium
• A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC 6273 (M 19)
• The usage of Stromgren photometry in studies of Local Group Dwarf Spheroidal Galaxies - Application to Draco: a new catalogue of Draco members and a study of the metallicity distribution function and radial gradients
• Four and one more: The formation history and total mass of globular clusters in the Fornax dSph
• The oxygen vs. sodium (anti)correlation(s) in omega Cen
• Influence of departures from LTE on calcium, titanium, and iron abundance determinations in cool giants of different metallicities
• The subgiant branch of omega Cen seen through high-resolution spectroscopy. I. The first stellar generation in omega Centauri?
• The Chemical Compositions of Very Metal-Poor Stars HD 122563 and HD 140283; A View From the Infrared
• On a new method to estimate distance, reddening and metallicity of RR Lyrae stars using optical/near-infrared ($B$,$V$,$I$,$J$,$H$,$K$) mean magnitudes: $\omega$ Centauri as a first test case
• Chemical Compositions of Field and Globular Cluster RR~Lyrae Stars: II. omega Centauri
• The GALAH Survey: Chemically tagging the Fimbulthul stream to the globular cluster $\omega$ Centauri
• The not so simple globular cluster $\omega$ Cen. I. Spatial distribution of the multiple stellar populations
• Empirical determination of the integrated red giant and horizontal branch stellar mass loss in omega Centauri
• Formation of stellar clusters
• The most metal-poor Galactic globular cluster: the first spectroscopic observations of ESO280-SC06
• Are the globular clusters with significant internal [Fe/H] spreads all former dwarf galaxy nuclei?
• The subgiant branch of omega Cen seen through high-resolution spectroscopy. II. The most metal-rich population
• Lithium abundance in lower red giant branch stars of Omega Centauri
• Four Metal-poor Stars in the Sagittarius Dwarf Spheroidal Galaxy
• A new formation model for omega Centauri: the crossroad of astrophysical processes
• Medium-resolution Spectroscopy of Red Giant Branch Stars in $\omega$ Centauri

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• oMEGACat I: MUSE spectroscopy of 300,000 stars within the half-light radius of $\omega$ Centauri
• On the separation between RR Lyrae and Type II Cepheids and their importance for distance determination: the case of $\omega$ Cen
• The HST large programme on $\omega$ Centauri -- V. Exploring the Ultracool Dwarf Population with Stellar Atmosphere and Evolutionary Modelling
• oMEGACat III. Multi-band photometry and metallicities reveal spatially well-mixed populations within $\omega$ Centauri's half-light radius
• Simulations of globular clusters within their parent galaxies: Metallicity spreads and anomalous precursor populations
• A stellar census in globular clusters with MUSE. A new perspective on the multiple main sequences of $\omega$ Centauri
• New constraints on the central mass contents of Omega Centauri from combined stellar kinematics and pulsar timing
• Beryllium abundances in turn-off stars of globular clusters with the CUBES spectrograph
• Kinematics of metallicity populations in Omega Centauri using Gaia Focused Product Release and Hubble Space Telescope
• The complex stellar system M 22: constraining the chemical enrichment from AGB stars using magnesium isotope ratios
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