Detailed Abundances for the Old Population near the Galactic Center: I. Metallicity distribution of the Nuclear Star Cluster

Abstract

We report the first high spectral resolution study of 17 M giants kinematically confirmed to lie within a few parsecs of the Galactic Center, using R=24,000 spectroscopy from Keck/NIRSPEC and a new linelist for the infrared K band. We consider their luminosities and kinematics, which classify these stars as members of the older stellar population and the central cluster. We find a median metallicity of <[Fe/H]>=-0.16 and a large spread from approximately -0.3 to +0.3 (quartiles). We find that the highest metallicities are [Fe/H]<+0.6, with most of the stars being at or below the Solar iron abundance. The abundances and the abundance distribution strongly resembles that of the Galactic bulge rather than disk or halo; in our small sample we find no statistical evidence for a dependence of velocity dispersion on metallicity.

arXiv comment18 pages, 14 figures, accepted for publication in AJ

References in corpus (49)

• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. V. Evidence for a wide age distribution and a complex MDF
• The Nuclear Bulge of the Galaxy. III. Large-Scale Physical Characteristics of Stars and Interstellar Matter
• SINFONI - Integral Field Spectroscopy at 50 milli-arcsecond resolution with the ESO VLT
• Interstellar Extinction Law toward the Galactic Center III: J, H, Ks bands in the 2MASS and the MKO systems, and 3.6, 4.5, 5.8, 8.0 micron in the Spitzer/IRAC system
• The IACOB project: I. Rotational velocities in Northern Galactic O and early B-type stars revisited. The impact of other sources of line-broadening
• Line derived infrared extinction towards the Galactic Center
• Surface Brightness Profile of the Milky Way's Nuclear Star Cluster
• The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass
• Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. VI. Age and abundance structure of the stellar populations in the central sub-kpc of the Milky Way
• An Extended Star Formation History for the Galactic Center from Hubble Space Telescope/NICMOS Observations
• Line lists for the A2PI-X2Sigma+ (red) and {B2Sigma+-X2Sigma} (violet) Systems of CN, 13C14N, and 12C15N, and Application to Astronomical Spectra
• The SDSS-III APOGEE Spectral Line List for H-band Spectroscopy
• Stellar Proper Motions in the Galactic Bulge from deep HST ACS/WFC Photometry
• The star formation history of the Milky Way's Nuclear Star Cluster
• Chemical Abundances of Luminous Cool Stars in the Galactic Center from High-Resolution Infrared Spectroscopy
• HST/WFPC2 proper motions in two bulge fields: kinematics and stellar population of the Galactic bulge
• The First Stellar Abundance Measurements in the Galactic Center: the M Supergiant IRS 7
• Really Cool Stars and the Star Formation History at the Galactic Center
• Chemical Abundances in Field Red Giants from High-Resolution H-Band Spectra using the APOGEE Spectral Linelist
• Kinematics of the old stellar population at the Galactic Center
• The Gaia-ESO Survey: Exploring the complex nature and origins of the Galactic bulge populations
• Stellar Iron Abundances at the Galactic Center
• A near-infrared survey of Miras and the distance to the Galactic Centre
• Mapping the Milky Way bulge at high resolution: the 3D dust extinction, CO, and X factor maps
• The Nuclear Cluster of the Milky Way: Total Mass and Luminosity (long version)
• KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars
• KMOS view of the Galactic Centre I. Young stars are centrally concentrated
• Discovery of low-metallicity stars in the central parsec of the Milky Way
• Detailed abundances for M giants in two inner bulge fields from Infrared Spectroscopy
• The chemical abundances in the Galactic Centre from the atmospheres of Red Supergiants
• What is limiting near-infrared astrometry in the Galactic Center?
• Experimental and theoretical oscillator strengths of Mg I for accurate abundance analysis
• Red Supergiant Stars as Cosmic Abundance Probes: NLTE Effects in J-band Iron and Titanium Lines
• Discovery of RR Lyrae Stars in the Nuclear Bulge of the Milky Way
• Chemical evolution of the inner 2 degrees of the Milky Way bulge: [alpha/Fe] trends and metallicity gradients
• Chemical Abundances of M giants in the Galactic Center: a Single Metal-Rich Population with Low [alpha/Fe]
• Near-Infrared Variability Study of the Central 2.3 arcmin x 2.3 arcmin of the Galactic Centre II. Identification of RR Lyrae Stars in the Milky Way Nuclear Star Cluster
• Detailed abundance analysis of a metal-poor giant in the Galactic Center
• Effects of the selection function on metallicity trends in spectroscopic surveys of the Milky Way
• Chemical evolution of the Galactic Center
• Laboratory oscillator strengths of Sc I in the near-infrared region for astrophysical applications
• Abundances of Na, Mg, and K in the atmospheres of red giant branch stars of Galactic globular cluster 47 Tucanae
• Dust within the old nuclear star cluster in the Milky Way
• Temperatures and metallicities of M giants in the galactic Bulge from low-resolution K-band spectra

Cited by in corpus (41)

• Nuclear Star Clusters
• Estimating stellar birth radii and the time evolution of the Milky Way's ISM metallicity gradient
• The Milky Way's nuclear star cluster: Old, metal-rich, and cuspy
• High Eccentricities and High Masses Characterize Gravitational-wave Captures in Galactic Nuclei as Seen by Earth-based Detectors
• Diversity of nuclear star cluster formation mechanisms revealed by their star formation histories
• Star Clusters in Evolving Galaxies
• The Milky Way's nuclear stellar disc: A dynamically cool and metal-rich component formed from the Central Molecular Zone?
• The inner two degrees of the Milky Way. Evidence of a chemical difference between the Galactic Center and the surrounding inner bulge stellar populations
• Super-Solar Metallicity Stars in the Galactic Center Nuclear Star Cluster: Unusual Sc, V, and Y Abundances
• Spectroscopic Detection of a Cusp of Late-type Stars around the Central Black Hole in the Milky Way
• Detailed abundances in the Galactic center: Evidence of a metal-rich alpha-enhanced stellar population
• The Star Formation History of the Milky Way's Nuclear Star Cluster
• Asymmetric spatial distribution of sub-solar metallicity stars in the Milky Way nuclear star cluster
• Abundances of disk and Bulge giants from high-resolution optical spectra III. Sc, V, Cr, Mn, Co, Ni
• Magnesium and silicon in interstellar dust: an X-ray overview
• Revealing the Formation of the Milky Way Nuclear Star Cluster via Chemo-Dynamical Modeling
• Disentangling the formation mechanisms of nuclear star clusters
• Evidence against anomalous compositions for giants in the Galactic Nuclear Star Cluster
• 2D kinematics of massive stars near the Galactic Center
• Chemical Characterization of the Inner Galactic bulge:North-South Symmetry
• Constraints on the Galactic Centre environment from Gaia hypervelocity stars
• Stellar Populations in the Transition Region of Nuclear Star Cluster and Nuclear Stellar Disc
• Kinematic data rebuild the Nuclear star cluster as the most metal rich region of the Galaxy
• M giants with IGRINS I. Stellar parameters and $\alpha$-abundance trends of the solar neighborhood population
• Comparing hypervelocity star populations from the Large Magellanic Cloud and the Milky Way
• Fluorine Abundances in the Galactic Nuclear Star Cluster
• Constraints on the Galactic Centre environment from Gaia hypervelocity stars II: The evolved population
• Detailed $\alpha$ abundance trends in the inner Galactic bulge
• Evidence of Deep Mixing in IRS 7, a Cool Massive Supergiant Member of the Galactic Nuclear Star Cluster
• Photometric Classification of Stars Around the Milky Way's Central Black Hole: I. Central Parsec
• A spectroscopic map of the Galactic centre -- Observations and resolved stars
• Measuring the alpha-abundance of subsolar-metallicity stars in the Milky Way's central half-parsec: testing globular cluster and dwarf galaxy infall scenarios
• On the manifest link between Terzan 5 and the Galactic bulge
• The S stars' zone of avoidance in the Galactic center
• Spatially resolving the atmosphere of the non-Mira-type AGB star SW Vir in near-infrared molecular and atomic lines with VLTI/AMBER
• A Wide Metallicity Range for Gyr-old Stars in the Nuclear Star Cluster
• The multi-zone chemical evolution of the Galactic bulge: predicting abundances for different radial zones
• New Temperature and Metallicity Scale of Cool Giants from K-band Spectra
• Chandra X-ray Measurement of Heavy Element Abundances of Wolf-Rayet Stars in the Galactic Center
• The Near-Infrared Spectrum of the Nuclear Star Cluster: Looking Below the Tip of the Iceberg and Comparisons with Extragalactic Nuclei
• Supergiant GCIRS 22 in the Milky Way Nuclear Star Cluster: Revised alpha abundances