Light and Heavy Element Abundance Variations in the Outer Halo Globular Cluster NGC 6229

Abstract

NGC 6229 is a relatively massive outer halo globular cluster that is primarily known for exhibiting a peculiar bimodal horizontal branch morphology. Given the paucity of spectroscopic data on this cluster, we present a detailed chemical composition analysis of 11 red giant branch members based on high resolution (R ~ 38,000), high S/N (> 100) spectra obtained with the MMT-Hectochelle instrument. We find the cluster to have a mean heliocentric radial velocity of -138.1${}_{-1.0}^{+1.0}$ km s${}^{-1}$, a small dispersion of 3.8${}_{-0.7}^{+1.0}$ km s${}^{-1}$, and a relatively low (M/L${}_{\mathrm{V}}$)${}_{\odot }$ = 0.82${}_{-0.28}^{+0.49}$. The cluster is moderately metal-poor with <[Fe/H]> = -1.13 dex and a modest dispersion of 0.06 dex. However, 18% (2/11) of the stars in our sample have strongly enhanced [La,Nd/Fe] ratios that are correlated with a small (~0.05 dex) increase in [Fe/H]. NGC 6229 shares several chemical signatures with M 75, NGC 1851, and the intermediate metallicity populations of omega Cen, which lead us to conclude that NGC 6229 is a lower mass iron-complex cluster. The light elements exhibit the classical (anti-)correlations that extend up to Si, but the cluster possesses a large gap in the O-Na plane that separates first and second generation stars. NGC 6229 also has unusually low [Na,Al/Fe] abundances that are consistent with an accretion origin. A comparison with M 54 and other Sagittarius clusters suggests that NGC 6229 could also be the remnant core of a former dwarf spheroidal galaxy.

Accepted for Publication in the Astronomical Journal; 19 pages; electronic tables available upon request or in the published manuscript

References in corpus (96)

• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Dartmouth Stellar Evolution Database
• Multiple populations in globular clusters. Lessons learned from the Milky Way globular clusters
• Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra
• Resolved Massive Star Clusters in the Milky Way and its Satellites: Brightness Profiles and a Catalogue of Fundamental Parameters
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Intrinsic iron spread and a new metallicity scale for Globular Clusters
• Na-O Anticorrelation and HB. VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• RVSAO 2.0: Digital Redshifts and Radial Velocities
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• Massive binaries as the source of abundance anomalies in globular clusters
• A new implementation of the infrared flux method using the 2MASS catalogue
• The Cannon: A data-driven approach to stellar label determination
• Spectroscopic and Photometric evidence of two stellar populations in the Galactic Globular Cluster NGC6121 (M4)
• Formation of omega Centauri from an ancient nucleated dwarf galaxy in the young Galactic disc
• Chemical Abundances for 855 Giants in the Globular Cluster Omega Centauri (NGC 5139)
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. V. Constraints on Formation Scenarios
• Early Disc Accretion as the Origin of Abundance Anomalies in Globular Clusters
• Yields of AGB and SAGB models with chemistry of low- and high-metallicity Globular Clusters
• The exotic chemical composition of the Sagittarius dwarf Spheroidal galaxy
• Globular Clusters with Tidal Tails: Deep Two-Color Star Counts
• 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 two metallicity groups of the globular cluster M22: a chemical perspective
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. III. A quintuple stellar population in NGC2808
• Chemistry of the Sagittarius Dwarf Galaxy: a Top-Light IMF, Outflows and the R-Process
• Two distinct halo populations in the solar neighborhood. II. Evidence from stellar abundances of Mn, Cu, Zn, Y, and Ba
• Line lists for the A2PI-X2Sigma+ (red) and {B2Sigma+-X2Sigma} (violet) Systems of CN, 13C14N, and 12C15N, and Application to Astronomical Spectra
• A unique model for the variety of multiple populations formation(s) in globular clusters: a temporal sequence
• Multiple stellar populations in the globular cluster NGC 1851
• An abundance analysis of bright giants in the globular cluster NGC 1851
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Abundances in giant stars of the globular cluster NGC 6752
• Sodium-oxygen anticorrelation and neutron capture elements in Omega Centauri stellar populations
• Pal 12 As A Part of the Sgr Stream; the Evidence From Abundance Ratios
• Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
• Neutron Capture Elements in s-Process-Rich, Very Metal-Poor Stars
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• Ruprecht 106: the first single population Globular Cluster?
• Star Clusters in M31: I. A Catalog and a Study of the Young Clusters
• Light, Alpha, and Fe-Peak Element Abundances in the Galactic Bulge
• Star Clusters in M31: V. Internal Dynamical Trends: Some Troublesome, Some Reassuring
• A General Abundance Problem for All Self-Enrichment Scenarios for the Origin of Multiple Populations in Globular Clusters
• A large C+N+O abundance spread in giant stars of the globular cluster NGC 1851
• Abundances for a large sample of red giants in NGC 1851: hints for a merger of two clusters?
• Sodium-Oxygen anticorrelation among Horizontal Branch Stars in the Globular Cluster M4
• Five groups of red giants with distinct chemical composition in the globular cluster NGC 2808
• High resolution spectroscopy of metal rich giants in omega Cen: first indication of SNe Ia enrichment
• Bimodality and Gaps on Globular Cluster Horizontal Branches. II. The Cases of NGC 6229, NGC 1851 and NGC 2808
• A 500 Parsec Halo Surrounding the Galactic Globular NGC 1851
• On the Distribution of Orbital Poles of Milky Way Satellites
• Constraints on the Formation of the Galactic Bulge from Na, Al, and Heavy Element Abundances in Plaut's Field
• A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)
• Ba stars and other binaries in first and second generation stars in globular clusters
• The Evolution of Copper in the Globular Cluster Omega Centauri
• The helium content of globular clusters: NGC6121 (M4)
• Terzan 8: a Sagittarius-flavoured globular cluster
• Calcium and light-elements abundance variations from high resolution spectroscopy in globular clusters
• Primordial r-process Dispersion in Metal-Poor Globular Clusters
• The Na-O anticorrelation in horizontal branch stars. I. NGC 2808
• Leo V: Spectroscopy of a Distant and Disturbed Satellite
• The primordial and evolutionary abundance variations in globular-cluster stars: a problem with two unknowns
• A Comparison of Copper Abundances in Globular Cluster and Halo Field Giant Stars
• The halo+cluster system of the Galactic globular cluster NGC1851
• The Outer Envelopes of Globular Clusters. I. NGC 7089 (M2)
• Accretion of pristine gas and dilution during the formation of multiple-population globular clusters
• Mass-to-Light Ratios for M31 Globular Clusters: Age-Dating and a Surprising Metallicity Trend
• The Na-O anticorrelation in horizontal branch stars. II. NGC1851
• A deep insight into the Mg-Al nucleosynthesis in massive AGBs and SAGB stars
• A search for stellar tidal debris of defunct dwarf galaxies around globular clusters in the inner Galactic halo
• The origin of the spurious iron spread in the globular cluster NGC 3201
• Detailed Chemical Abundances in NGC 5824: Another Metal-Poor Globular Cluster with Internal Heavy Element Abundance Variations
• The mosaic multiple stellar populations in $\omega$ Centauri : the Horizontal Branch and the Main Sequence
• A Chemical Composition Survey of the Iron-Complex Globular Cluster NGC 6273 (M 19)
• The Origin and Chemical Evolution of the Exotic Globular Cluster NGC3201
• A critical look at the merger scenario to explain multiple populations and rotation in iron-complex globular clusters
• A comprehensive chemical abundance study of the outer halo globular cluster M 75
• Spectroscopic analysis of the two subgiant branches of the globular cluster NGC1851
• Chemical characterization of the globular cluster NGC 5634 associated to the Sagittarius dwarf spheroidal galaxy
• The fraction of first and second generation stars in globular clusters. I The case of NGC 6752
• The Na-O anticorrelation in horizontal branch stars. V. NGC 6723
• Chemical Complexity in the Eu-enhanced Monometallic Globular Cluster NGC 5986
• Two New Halo Debris Streams in the Sloan Digital Sky Survey
• NGC 5694: another foster son of the Galactic Halo
• Revisiting the variable star population in NGC~6229 and the structure of the Horizontal Branch
• From the CMD of Omega Centauri and (super-)AGB stellar models to a Galactic plane passage gas purging chemical evolution scenario
• A broad perspective on multiple abundance populations in the globular cluster NGC 1851
• M75, a Globular Cluster with a Trimodal Horizontal Branch. I. Color-Magnitude Diagram
• Stellar Photometry of the Globular Cluster NGC 6229. I. Data Reduction and Morphology of the Brighter Part of the CMD
• PERIGALACTIC DISTANCES OF GLOBULAR CLUSTERS
• The outer-halo globular cluster NGC 6229. IV. Variable stars
• The subgiant branch of omega Cen seen through high-resolution spectroscopy. II. The most metal-rich population
• Abundance analysis of the outer halo globular cluster Palomar 14
• Kinematics of a globular cluster with an extended profile: NGC5694
• A sequence of nitrogen-rich very red giants in the globular cluster NGC 1851

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• NGC 1261: an $r$-process enhanced globular cluster from the Gaia-Enceladus event
• An outer shade of Pal: Abundance analysis of the outer halo globular cluster Palomar 13
• Globular Cluster Intrinsic Iron Abundance Spreads: II. Protocluster Metallicities and the Age-Metallicity Relations of Milky Way Progenitors
• On the photometric metallicity of Oosterhoff-type I and II RRab stars
• Chemical composition of the outer halo globular cluster Palomar 15
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