The impact of carbon and oxygen abundances on the metal-poor initial mass function

Abstract

Star formation models predict that the metal-poor initial mass function (IMF) can be substantially different from that observed in the metal-rich Milky Way. This changeover occurs because metal-poor gas clouds cool inefficiently due to their lower abundance of metals and dust. However, predictions for the metal-poor IMF to date rely on assuming Solar-scaled abundances, that is, [X/O] = 0 at all [O/H]. There is now growing evidence that elements such as C and O that dominate metal line cooling in the ISM do not follow Solar scaling at low metallicities. In this work, we extend models that predict the variation in the characteristic (or, the peak) IMF mass as a function of metallicity using [C/O] ratios derived from observations of metal-poor Galactic stars and of H II regions in dwarf galaxies. These data show [C/O] < 0 at sub-Solar [O/H], which leads to a substantially different metal-poor IMF in the metallicity range where C I and C II cooling dominate ISM thermodynamics, resulting in an increase in the characteristic mass by a factor as large as 7. An important consequence of this difference is a shift in the location of the transition from a top- to a bottom-heavy IMF upwards by 0.5 $-$ 1 dex in metallicity. Our findings indicate that the IMF is very sensitive to the assumptions around Solar-scaled ISM compositions in metal-poor systems (e.g., dwarf galaxies, the Galactic halo and metal-poor stars) that are a key focus of JWST.

14 pages, 8 figures. Accepted by MNRAS

References in corpus (84)

• Array Programming with NumPy
• The GALAH+ Survey: Third Data Release
• The Resolved Properties of Extragalactic Giant Molecular Clouds
• Carbon Enhanced Metal-Poor Stars. I. Chemical Compositions of 26 Stars
• The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• On the Star Formation Efficiency of Turbulent Magnetized Clouds
• Physical properties of molecular clouds for the entire Milky Way disk
• An extremely primitive halo star
• Fragmentation of star-forming clouds enriched with the first dust
• The Metallicity of Galaxy Disks: Infall versus Outflow
• HI-to-H2 Transitions and H I Column Densities in Galaxy Star-Forming Regions
• Probing the Formation of the First Low-Mass Stars with Stellar Archaeology
• Ultraviolet Emission Lines in Young Low Mass Galaxies at z~2: Physical Properties and Implications for Studies at z>7
• Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
• 3D Hydrodynamical Simulations of Surface Convection in Red Giant Stars. Impact on spectral line formation and abundance analysis
• Keck HIRES Spectroscopy of Extragalactic HII Regions: C and O Abundances from Recombination Lines
• TOPoS: II. On the bimodality of carbon abundance in CEMP stars. Implications on the early chemical evolution of galaxies
• Tracing the total molecular gas in galaxies: [CII] and the CO-dark gas
• On the abundance discrepancy problem in HII regions
• Evolution and nucleosynthesis of asymptotic giant branch stellar models of low metallicity
• HE 1327-2326, an unevolved star with [Fe/H]<-5.0. II. New 3D-1D corrected abundances from a VLT/UVES spectrum
• Sulphur and zinc abundances in Galactic halo stars revisited
• The localized chemical pollution in NGC 5253 revisited: Results from deep echelle spectrophotometry
• The Chemical Evolution of Carbon, Nitrogen, and Oxygen in Metal-Poor Dwarf Galaxies
• Carbon and oxygen abundances in stellar populations
• Variations of the stellar initial mass function in the progenitors of massive early-type galaxies and in extreme starburst environments
• Gravitationally Lensed Galaxies at 2<z<3.5: Direct Abundance Measurements of Lya Emitters
• A First Look at the Abundance Pattern -- O/H, C/O, and Ne/O -- in $z>7$ Galaxies with JWST/NIRSpec
• Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution
• The statistical properties of stars and their dependence on metallicity
• The chemical compositions of the extreme halo stars HE0107-5240 and HE1327-2326 inferred from 3D hydrodynamical model atmospheres
• The statistical properties of stars and their dependence on metallicity: the effects of opacity
• Galaxy And Mass Assembly (GAMA): A forensic SED reconstruction of the cosmic star formation history and metallicity evolution by galaxy type
• Physical Properties of Molecular Clouds at 2 parsec Resolution in the Low-Metallicity Dwarf Galaxy NGC 6822 and the Milky Way
• Detailed dust modelling in the L-Galaxies semi-analytic model of galaxy formation
• Carbon and oxygen in HII regions of the Magellanic Clouds: abundance discrepancy and chemical evolution
• Understanding star formation in molecular clouds II. Signatures of gravitational collapse of IRDCs
• HD and H2 formation in low-metallicity dusty gas clouds at high redshift
• First Insights into the ISM at $z>8$ with JWST: Possible Physical Implications of a High [O III]$\lambda 4363$/[O III]$\lambda 5007$
• Temperature and Metallicity Gradients in the Hot Gas Outflows of M82
• The lowest detected stellar Fe abundance: The halo star SMSS J160540.18-144323.1
• CLASSY IV: Exploring UV diagnostics of the interstellar medium in local high-$z$ analogs at the dawn of the JWST era
• The Physical Conditions in a Pre Super Star Cluster Molecular Cloud in the Antennae Galaxies
• The physics of gas phase metallicity gradients in galaxies
• Dust scaling relations in a cosmological simulation
• Evidence for an aspherical Population III supernova explosion inferred from the hyper metal-poor star HE1327-2326
• Carbon-enhanced metal-poor stars: a window on AGB nucleosynthesis and binary evolution. I. Detailed analysis of 15 binary stars with known orbital periods
• The Pristine survey VIII: The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime
• The origin of dust in galaxies across cosmic time
• Metallicity dependence of the H/H${}_2$ and C${}^{+}$/C/CO distributions in a resolved self-regulating interstellar medium
• Impact of the cosmic background radiation on the initial mass function of metal-poor stars
• Zero-metallicity hypernova uncovered by an ultra metal-poor star in the Sculptor dwarf spheroidal galaxy
• The Pristine Inner Galaxy Survey (PIGS) II: Uncovering the most metal-poor populations in the inner Milky Way
• Ultra-faint dwarf galaxies: unveiling the minimum mass of the first stars
• BACCHUS Analysis of Weak Lines in APOGEE Spectra (BAWLAS)
• 3D non-LTE line formation of neutral carbon in the Sun
• Carbon and oxygen in metal-poor halo stars
• Carbon monoxide in an extremely metal-poor galaxy
• Magnetic field amplification in accretion discs around the first stars: implications for the primordial IMF
• Discovery of the most metal-poor damped Lyman-alpha system
• Chemical Abundance Analysis of Three $\alpha$-Poor, Metal-Poor Stars in the Ultra-Faint Dwarf Galaxy Horologium I
• Supernova dust formation and the grain growth in the early universe: The critical metallicity for low-mass star formation
• Metallicity, ionization parameter, and pressure variations of HII regions in the TYPHOON spiral galaxies
• Metallicity and the Universality of the IMF
• On the origin of the mass-metallicity gradient relation in the local Universe
• The Most Metal-Poor Stars. V. The CEMP-no Stars in 3D and Non-LTE
• On the variation of carbon abundance in galaxies and its implications
• Combining radiative transfer and diffuse interstellar medium physics to model star formation
• The DUVET Survey: Direct $T_e$-based metallicity mapping of metal-enriched outflows and metal-poor inflows in Mrk 1486
• Origin of the CEMP-no Group Morphology in the Milky Way
• High resolution spectroscopic follow-up of the most metal-poor candidates from SkyMapper DR1.1
• The MASSIVE SURVEY XVI. The Stellar Initial Mass Function in the Center of MASSIVE Early-Type Galaxies
• New Insights into the Physical Conditions and Internal Structure of a Candidate Proto-Globular Cluster
• The chemical abundance pattern of the extremely metal-poor thin disk star 2MASS J1808-5104 and its origins
• An in-depth spectroscopic examination of molecular bands from 3D hydrodynamical model atmospheres. II. Carbon-enhanced metal-poor 3D model atmospheres
• The Molecular Clouds Fueling a 1/5 Solar Metallicity Starburst
• Stromlo Stellar Tracks: non-solar scaled abundances for massive stars
• On the origin of nitrogen at low metallicity
• First extragalactic measurement of the turbulence driving parameter: ALMA observations of the star-forming region N159E in the Large Magellanic Cloud
• HI-to-H${}_2$ Transitions in Dust-Free Interstellar Gas
• Chemical evolution of ultra-faint dwarf galaxies: testing the IGIMF
• The metallic winds in dwarf galaxies
• The effect of metallicity on the abundances of molecules in protoplanetary disks

Cited by in corpus (6)

• Tracing Pop III supernovae with extreme energies through the Sculptor dwarf spheroidal galaxy
• The earliest phases of CNO enrichment in galaxies
• Metallicity dependence of the CO-to-H${}_2$ and the [CI]-to-H${}_2$ conversion factors in galaxies
• Population III star formation in the presence of turbulence, magnetic fields and ionizing radiation feedback
• Fluorine abundances in CEMP stars at the lowest metallicity: Hints on the nature of the first stars
• SILCC -- IX. The multi-phase interstellar medium at low metallicity