Observational evidence for a different IMF in the early Galaxy

Abstract

The unexpected high incidence of carbon-enhanced, s-process enriched unevolved stars amongst extremely metal-poor stars in the halo provides a significant constraint on the Initial Mass Function (IMF) in the early Galaxy. We argue that these objects are evidence for the past existence of a large population of intermediate-mass stars, and conclude that the IMF in the early Galaxy was different from the present, and shifted toward higher masses.

14 pages, 1 color figure, accepted for publication on ApJ

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• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• A Comprehensive Analysis of Uncertainties Affecting the Stellar Mass - Halo Mass Relation for 0<z<4
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
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• The galaxy stellar mass-star formation rate relation: Evidence for an evolving stellar initial mass function?
• The stellar halo of the Galaxy
• The propagation of uncertainties in stellar population synthesis modeling II: The challenge of comparing galaxy evolution models to observations
• Galaxy And Mass Assembly (GAMA): The star formation rate dependence of the stellar initial mass function
• The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sample
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• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• Chemical Evolution in Hierarchical Models of Cosmic Structure II: The Formation of the Milky Way Stellar Halo and the Distribution of the Oldest Stars
• Chemical Evolution in Hierarchical Models Of Cosmic Structure I: Constraints on the Early Stellar Initial Mass Function
• Wind Roche-lobe overflow: Application to carbon-enhanced metal-poor stars
• Carbon-enhanced Metal-poor Stars in SDSS/SEGUE. I. Carbon Abundance Estimation and Frequency of CEMP Stars
• Population Synthesis of Binary Carbon-enhanced Metal-poor Stars
• Do most planetary nebulae derive from binaries? I Population synthesis model of the galactic planetary nebula population produced by singlestars and binaries
• The Most Metal-Poor Stars. III. The Metallicity Distribution Function and CEMP Fraction
• The Origin of Carbon-Enhancement and Initial Mass Function of Extremely Metal-Poor Stars in the Galactic Halo
• Gas-Rich Mergers in LCDM: Disk Survivability and the Baryonic Assembly of Galaxies
• The mmax-Mecl relation, the IMF and IGIMF: probabilistically sampled functions?
• Low-Metallicity Star Formation : Prestellar Collapse and Protostellar Accretion in the Spherical Symmetry
• Thermohaline mixing and gravitational settling in carbon-enhanced metal-poor stars
• The galaxy-wide IMF of dwarf late-type to massive early-type galaxies
• A high-resolution spectral analysis of three carbon-enhanced metal-poor stars
• Chemo-Archaeological Downsizing in a Hierarchical Universe: Impact of a Top Heavy IGIMF
• Is Extra Mixing Really Needed in Asymptotic Giant Branch Stars?
• Metals, dust and the cosmic microwave background: fragmentation of high-redshift star-forming clouds
• The Stellar Abundances for Galactic Archaeology (SAGA) Database III - Analysis of Enrichment Histories for Elements and Two Modes of Star Formation during the Early Evolution of Milky Way
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• Lithium abundances in CEMP stars
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• The Chemical Evolution of Helium in Globular Clusters: Implications for the Self-Pollution Scenario
• Carbon-Enhanced Metal-Poor Stars, the Cosmic Microwave Background, and the Stellar IMF in the Early Universe
• The evolution of low-metallicity asymptotic giant branch stars and the formation of carbon-enhanced metal-poor stars
• Carbon-Enhanced Hyper-metal-poor Stars and the Stellar IMF at Low Metallicity
• Modelling the observed properties of carbon-enhanced metal-poor stars using binary population synthesis
• How plausible are the proposed formation scenarios of CEMP-r/s stars?
• Top-heavy integrated galactic stellar initial mass functions (IGIMFs) in starbursts
• Transition of the Stellar Initial Mass Function Explored with Binary Population Synthesis
• The occurrence of nitrogen-enhanced metal-poor stars: implications for the initial mass function in the early Galactic halo
• Light element abundances in carbon-enhanced metal-poor stars
• Origin of the CEMP-no Group Morphology in the Milky Way
• Spectroscopic study of CEMP-(s & r/s) stars- Revisiting classification criteria and formation scenarios, highlighting i-process nucleosynthesis
• The CH fraction of Carbon stars at high Galactic latitudes
• Chemical analysis of CH stars - I: atmospheric parameters and elemental abundances
• Chemical analysis of CH stars - II: atmospheric parameters and elemental abundances
• Physical Mechanism for the Intermediate Characteristic Stellar Mass in the Extremely Metal-poor Environments
• Subaru/HDS study of CH stars: elemental abundances for stellar neutron-capture process studies
• Where are the Cosmic Metals at z~3?
• Carbon-enhanced Metal-poor Stars in SDSS/SEGUE. II. Comparison of CEMP Star Frequencies with Binary Population Synthesis Models
• The Polytropic Equation of State of Primordial Gas Clouds
• The Cosmic Evolution of Magnesium Isotopes
• The Cosmic Microwave Background and the Stellar Initial Mass Function
• Origins of carbon-enhanced metal-poor stars
• Early-Age Evolution of the Milky Way Related by Extremely Metal-Poor Stars
• Predicting metallicities and carbon abundances from Gaia XP spectra for (carbon-enhanced) metal-poor stars
• Polarimetric studies of carbon stars at high Galactic latitude
• Galaxy formation with cold gas accretion and evolving stellar initial mass function
• The Puzzling Frequencies of CEMP and NEMP Stars
• Extremely Metal-Poor Stars and a Hierarchical Chemical Evolution Model
• Spectroscopic study of Ba and CEMP-s stars: Mass distribution of AGB progenitors
• Thermal Regulation and the Star-Forming Main Sequence
• A Catalog of 12,766 Carbon-enhanced Metal-poor Stars from LAMOST Data Release 8
• Modelling the evolution and nucleosynthesis of carbon-enhanced metal-poor stars
• Binary Populations of Carbon-Enhanced Metal-Poor Stars
• i-process nucleosynthesis: observational evidences from CEMP stars
• The evolved pulsating CEMP star HD112869
• The elusive origin of Carbon-Enhanced Metal-Poor stars