The Chemical Composition of the Galactic Bulge and Implications for its Evolution

Abstract

The average bulge [Fe/H] and [Mg/H] are +0.06 and +0.17 dex, respectively, in Baade's Window, roughly 0.2 dex higher than the thin disk and ~0.7 dex higher than the local thick disk metallicity. This suggests a higher effective yield in the bulge, perhaps due to more efficient retention of supernova ejecta. The bulge vertical [Fe/H] gradient, at ~0.5 dex/kpc, appears to be due to a changing mixture of sub-populations (near +0.3 dex and -0.3 dex and one possibly near -0.7 dex) with latitude. The bulge is enhanced in O, Mg, Si, Ca, Ti, and Al relative to the sun, with [alpha/Fe]=+0.15 dex at [Fe/H]=0.0 dex. Below [Fe/H]~-0.5 dex, the bulge and local thick disk compositions are very similar, but small [Mg/Fe] and possibly [<SiCaTi>/Fe] enhancements, low [La/Eu] ratios and large [Cu/Fe], relative to the thick disk suggest slightly higher SFR in the bulge. However, these composition differences could simply be due to measurement errors and non-LTE effects. Unfortunately, comparison with the thick disk near solar [Fe/H] suffers considerable confusion, due to poor identification of the local thick disk. Unusual zig-zag abundance trends of [Cu/Fe] and [Na/Fe] suggest nucleosynthesis dominated by core-collapse supernovae with metallicity-dependent yields, in the Type~Ia supernova time-delay scenario. Thus, the bulge sub-population compositions resemble the local thin and thick disks, but at higher [Fe/H], suggesting a radial [Fe/H] gradient in both the thin and thick disks, within the solar circle, near -0.04 to -0.05 dex/kpc. If the bulge was built through accretion of inner disk stars by a bar, it appears that the inner thin and thick disk stars, incorporated into the bulge, retained vertical scale heights characteristic of their kinematic origin, and resulting in the vertical [Fe/H] gradient and [alpha/Fe] trends seen today.

arXiv comment40 pages, 21 figures. This review paper submitted to PASA. Version 2 updates Figure 10 and comments to it. final version: included various missing bibliographic entries

References in corpus (65)

• The chemical composition of the Sun
• Core-Collapse Supernovae from 9 to 120 Solar Masses Based on Neutrino-powered Explosions
• Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars
• Galactic Chemical Evolution: Hydrogen Through Zinc
• Elemental Abundance Survey of The Galactic Thick Disk
• Galactic chemical evolution: Carbon through Zinc
• The Chemical Compositions of Galactic Disk F and G Dwarfs
• Galactic Evolution of Sr, Y, Zr: A Multiplicity of Nucleosynthetic Processes
• Production of all the r-process nuclides in the dynamical ejecta of neutron star mergers
• Neutron-Capture Elements in the Early Galaxy: Insights from a Large Sample of Metal-Poor Giants
• R-Process Nucleosynthesis in Dynamically Ejected Matter of Neutron Star Mergers
• Abundance Patterns in the Draco, Sextans and Ursa Minor Dwarf Spheroidal Galaxies
• VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies: I. Nucleosynthesis and Abundance Ratios
• Abundances and Kinematics of Field Halo and Disk Stars I: Observational Data and Abundance Analysis
• Morphology, photometry and kinematics of N-body bars. I Three models with different halo central concentrations
• Evolution, nucleosynthesis and yields of low mass AGB stars
• Evolution, nucleosynthesis and yields of low mass AGB stars at different metallicities (II): the FRUITY database
• Mapping the Three-Dimensional Density of the Galactic Bulge with VVV Red Clump Stars
• The Rise of the s-Process in the Galaxy
• NLTE line formation of Fe in late-type stars II: 1D spectroscopic stellar parameters
• Sub-Chandrasekhar Mass Models For Type Ia Supernovae
• ARGOS III: Stellar Populations in the Galactic Bulge of the Milky Way
• Two Red Clumps and the X-Shaped Milky Way Bulge
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• Three-dimensional pure deflagration models with nucleosynthesis and synthetic observables for Type Ia supernovae
• Abundances of Baade's Window Giants from Keck/HIRES Spectra: II. The Alpha- and Light Odd Elements
• Oxygen Abundances in Nearby FGK Stars and the Galactic Chemical Evolution of the Local Disk and Halo
• The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models
• Atomic Diffusion and Mixing in Old Stars I. VLT/FLAMES-UVES Observations of Stars in NGC 6397
• Fundamental Parameters and Chemical Composition of Arcturus
• The supernova delay time distribution in galaxy clusters and implications for Type-Ia progenitors and metal enrichment
• The s process in massive stars at low metallicity. Effect of primary N14 from fast rotating stars
• Abundances of Baade's Window Giants from Keck/HIRES Spectra: I. Stellar Parameters and [Fe/H] Values
• Chemistry of the Sagittarius Dwarf Galaxy: a Top-Light IMF, Outflows and the R-Process
• NLTE analysis of Co I/Co II lines in spectra of cool stars with new laboratory hyperfine splitting constants
• Abundances and Kinematics of Field Stars II: Kinematics and Abundance Relationships
• A Determination of the Thick Disk Chemical Abundance Distribution: Implications for Galaxy Evolution
• The r-process in supernova explosions from the collapse of O-Ne-Mg cores
• The First Detailed Abundances for M giants in Baade's Window from Infrared Spectroscopy
• Light, Alpha, and Fe-Peak Element Abundances in the Galactic Bulge
• Ionization balance of Ti in the photospheres of the Sun and four late-type stars
• The Chemical Evolution of the Ursa Minor Dwarf Spheroidal Galaxy
• A Chandrasekhar Mass Progenitor for the Type Ia Supernova Remnant 3C 397 from The Enhanced Abundances of Nickel and Manganese
• K Giants in Baade's Window. II. The Abundance Distribution
• Chemical Evolution of the Galactic Bulge as Derived from High-Resolution Infrared Spectroscopy of K and M Red Giants
• Subaru/HDS Abundances in Three Giant Stars in the Ursa Minor Dwarf Spheroidal Galaxy
• Iron-Group Abundances in the Metal-Poor Main Sequence Turnoff Star HD~84937
• Constraints on the Formation of the Galactic Bulge from Na, Al, and Heavy Element Abundances in Plaut's Field
• Metal-poor stars towards the Galactic bulge - a population potpourri
• Manganese Abundances in Cluster and Field Stars
• A Comparison of Copper Abundances in Globular Cluster and Halo Field Giant Stars
• Rates, Progenitors and Cosmic Mix of Type Ia Supernovae
• The Evolution of Oxygen and Magnesium in the Bulge and Disk of the Milky Way
• The disc origin of the Milky Way bulge
• The Milky Way without X: An alternative interpretation of the double red clump in the Galactic bulge
• Subclasses of Type Ia Supernovae as the origin of [α/Fe] ratios in dwarf spheroidal galaxies
• Chemical evolution of the inner 2 degrees of the Milky Way bulge: [alpha/Fe] trends and metallicity gradients
• The Metallicity Distribution of the Milky Way Bulge
• Mn abundances in the stars of the Galactic disc with metallicities -1.0 < [Fe/H] < 0.3
• Heavy elements Ba, La, Ce, Nd, and Eu in 56 Galactic bulge red giants
• Fluorine Abundances in the Milky Way Bulge
• Non-LTE analysis of neutral copper in the late-type metal-poor stars
• Understanding AGB evolution in Galactic bulge stars from high-resolution infrared spectroscopy
• Non-LTE radiative transfer in cool stars. Theory and applications to the abundance analysis for 24 chemical elements
• Manganese Abundances in the Globular Cluster Omega Centauri

Cited by in corpus (46)

• Chemodynamical history of the Galactic Bulge
• 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
• From the bulge to the outer disc: StarHorse stellar parameters, distances, and extinctions for stars in APOGEE DR16 and other spectroscopic surveys
• The GIRAFFE Inner Bulge Survey (GIBS) III. Metallicity distributions and kinematics of 26 Galactic bulge fields
• High-precision stellar abundances of the elements - methods and applications
• Phylogeny of the Milky Way's inner disk and bulge populations: Implications for gas accretion, (the lack of) inside-out thick disk formation, and quenching
• The age of the Milky Way inner stellar spheroid from RR Lyrae population synthesis
• The Gaia-ESO Survey: Galactic evolution of sulphur and zinc
• BACCHUS Analysis of Weak Lines in APOGEE Spectra (BAWLAS)
• Observational constraints on the origin of the elements. III. Evidence for the dominant role of sub-Chandrasekhar SN Ia in the chemical evolution of Mn and Fe in the Galaxy
• Exploring the stellar age distribution of the Milky Way Bulge using APOGEE
• The Fastest Travel Together: Chemical Tagging of the Fastest Stars in Gaia DR2 to the Stellar Halo
• Mapping the stellar age of the Milky Way bulge with the VVV. I. The method
• Abundances of disk and bulge giants from high-resolution optical spectra -- IV. Zr, La, Ce, Eu
• Abundances of disk and Bulge giants from high-resolution optical spectra III. Sc, V, Cr, Mn, Co, Ni
• On the Use of Field RR Lyrae as Galactic Probes. III. The $\alpha$-element abundances
• The COMBS survey I: Chemical Origins of Metal-Poor Stars in the Galactic Bulge
• Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques
• Blanco DECam Bulge Survey (BDBS) II: Project Performance, Data Analysis, and Early Science Results
• Iron-peak elements Sc, V, Mn, Cu and Zn in Galactic bulge globular clusters
• High-resolution abundance analysis of four red giants in the globular cluster NGC 6558
• Oxygen and zinc abundances in 417 Galactic bulge red giants
• Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569
• Unusual neutron-capture nucleosynthesis in a carbon-rich Galactic bulge star
• Discovery of carbon-rich Miras in the Galactic bulge
• NLTE analysis of copper lines in different stellar populations
• Gauging Metallicity of Diffuse Gas Under An Uncertain Ionizing Radiation Field
• HERBS I: Metallicity and alpha enhancement along the Galactic bulge minor axis
• The Blanco DECam Bulge Survey. I. The Survey Description and Early Results
• Chemical abundances in the metal-intermediate GC NGC 6723
• Abundance analysis of APOGEE spectra for 58 metal-poor stars from the bulge spheroid
• HERBS II: Detailed chemical compositions of Galactic bulge stars
• Spectroscopic study of the elusive globular cluster ESO452-SC11 and its surroundings
• Detailed chemical abundance analysis of the thick disk star cluster Gaia 1
• Stellar Population and Elemental Abundance Gradients of Early-type Galaxies
• Difference in chemical composition between the bright and faint red clump stars in the Milky Way bulge
• Chemical analysis of eight giant stars of the globular cluster NGC 6366
• Cobalt and copper abundances in 56 Galactic bulge red giants
• Impact of distance determinations on Galactic structure. II. Old tracers
• Populating The Milky Way: Characterising Planet Demographics by Combining Galaxy Formation Simulations and Planet Population Synthesis Models
• NLTE Analysis of Copper Abundances in the Galactic Bulge Stars
• Integrated Spectra of Milky Way Globular Cluster
• Abundances of disk and bulge giants from high-resolution optical spectra V. Molybdenum -- the p-process element
• The first r-process enhanced star confirmed to be a member of the Galactic bulge
• Rediscovering the Milky Way with orbit superposition approach and APOGEE data III. Panoramic view of the bulge
• UVES analysis of red giants in the bulge globular cluster NGC 6522