Direct Constraints on the Extremely Metal-Poor Massive Stars Underlying Nebular C IV Emission from Ultra-Deep HST/COS Ultraviolet Spectroscopy

Abstract

Metal-poor nearby galaxies hosting massive stars have a fundamental role to play in our understanding of both high-redshift galaxies and low metallicity stellar populations. But while much attention has been focused on their bright nebular gas emission, the massive stars that power it remain challenging to constrain. Here we present exceptionally deep Hubble Space Telescope ultraviolet spectra targeting six galaxies that power strong nebular C IV emission approaching that encountered at $z>6$. We find that the strength and spectral profile of the nebular C IV in these new spectra follow a sequence evocative of resonant scattering models, indicating that the hot circumgalactic medium likely plays a key role in regulating C IV escape locally. We constrain the metallicity of the massive stars in each galaxy by fitting the forest of photospheric absorption lines, reporting measurements driven by iron that lie uniformly below 10% solar. Comparison with the gas-phase oxygen abundances reveals evidence for enhancement in O/Fe above solar across the sample, robust to assumptions about the absolute gas-phase metallicity scale. This supports the idea that these local systems are more chemically-similar to their primordial high-redshift counterparts than to the bulk of nearby galaxies. Finally, we find significant tension between the strong stellar wind profiles observed and our population synthesis models constrained by the photospheric forest in our highest-quality spectra. This reinforces the need for caution in interpreting wind lines in isolation at high-redshift, but also suggests a unique path towards validating fundamental massive star physics at extremely low metallicity with integrated ultraviolet spectra.

arXiv comment34 pages, 14 figures, submitted to AAS Journals

References in corpus (120)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• Stellar population synthesis at the resolution of 2003
• The chemical composition of the Sun
• Galactic Stellar and Substellar Initial Mass Function
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• Correcting for the Effects of Interstellar Extinction
• MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• Rest-Frame Ultraviolet Spectra of z~3 Lyman Break Galaxies
• A Quantitative Comparison of SMC, LMC, and Milky Way UV to NIR Extinction Curves
• The ages and metallicities of galaxies in the local universe
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• Galactic chemical evolution: Carbon through Zinc
• Solar Chemical Abundances Determined with a CO5BOLD 3D Model Atmosphere
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• Nucleosynthesis Yields of Core-Collapse Supernovae and Hypernovae, and Galactic Chemical Evolution
• The chemical make-up of the Sun: A 2020 vision
• De Re Metallica: The cosmic chemical evolution of galaxies
• The chemical composition of metal-poor emission-line galaxies in the Data Release 3 of the Sloan Digital Sky Survey
• PARSEC evolutionary tracks of massive stars up to $350M_{\odot }$ at metallicities 0.0001$\le Z\le$0.04
• Near-Field Cosmology with Metal-Poor Stars
• The First Galaxies
• VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies: I. Nucleosynthesis and Abundance Ratios
• 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
• 3D Lyman-alpha radiation transfer. I. Understanding Lyman-alpha line profile morphologies
• Nebular Emission from Star-Forming Galaxies
• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• Modelling and interpreting spectral energy distributions of galaxies with BEAGLE
• Reconciling the Stellar and Nebular Spectra of High Redshift Galaxies
• Our Peculiar Motion Away from the Local Void
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• Spectral synthesis including massive binaries
• Dynamic nested sampling: an improved algorithm for parameter estimation and evidence calculation
• A Library of Theoretical Ultraviolet Spectra of Massive, Hot Stars for Evolutionary Synthesis
• Quantitative Spectroscopy of O Stars at Low Metallicity. O Dwarfs in NGC 346
• The Connection Between Galaxies and Intergalactic Absorption Lines at Redshift 2<z<3
• The photospheric solar oxygen project: I. Abundance analysis of atomic lines and influence of atmospheric models
• The Ultraviolet Spectroscopic Properties of Local Starbursts: Implications at High-Redshift
• Nebular Emission Line Ratios in z~2-3 Star-Forming Galaxies with KBSS-MOSFIRE: Exploring the Impact of Ionization, Excitation, and Nitrogen-to-Oxygen Ratio
• Low mass loss rates in O-type stars: Spectral signatures of dense clumps in the wind of two Galactic O4 stars
• The Metallicity of Galaxy Disks: Infall versus Outflow
• Spectroscopic detection of CIV in a galaxy at z=7.045: Implications for the ionizing spectra of reionization-era galaxies
• The COS-Dwarfs Survey: The Carbon Reservoir Around sub-L* Galaxies
• Segue 1: An Unevolved Fossil Galaxy from the Early Universe
• A systematic metallicity study of DustPedia galaxies reveals evolution in the dust-to-metal ratios
• Spectral models for binary products: Unifying Subdwarfs and Wolf-Rayet stars as a sequence of stripped-envelope stars
• Wind modelling of very massive stars up to 300 solar masses
• Ultraviolet spectra of extreme nearby star-forming regions --- approaching a local reference sample for JWST
• The MOSDEF Survey: Direct-Method Metallicities and ISM Conditions at $z\sim 1.5-3.5$
• On the abundance discrepancy problem in HII regions
• Carbon and Oxygen Abundances in Low Metallicity Dwarf Galaxies
• The ages of young star clusters, massive blue stragglers and the upper mass limit of stars: analysing age dependent stellar mass functions
• Heavy elements in Galactic and Magellanic Cloud HII regions: recombination-line versus forbidden-line abundances
• The Origin of C IV Absorption Systems at Redshifts z<1---Discovery of Extended C IV Envelopes Around Galaxies
• The Chemical Evolution of Carbon, Nitrogen, and Oxygen in Metal-Poor Dwarf Galaxies
• A downturn in intergalactic CIV as redshift 6 is approached
• Spectral Modelling of Star-Forming Regions in the Ultraviolet: Stellar Metallicity Diagnostics for High Redshift Galaxies
• Constraining the metallicities, ages, star formation histories, and ionizing continua of extragalactic massive star populations
• Abundances for metal-poor stars with accurate parallaxes II. alpha-elements in the halo
• Constraints on the production and escape of ionizing radiation from the emission-line spectra of metal-poor star-forming galaxies
• Metal-enriched galactic outflows shape the mass-metallicity relationship
• The effect of stellar evolution uncertainties on the rest-frame ultraviolet stellar lines of CIV and HeII in high-redshift Lyman-break galaxies
• Deep Hubble Space Telescope/ACS Observations of I Zw 18: a Young Galaxy in Formation
• Measuring the Physical Conditions in High-Redshift Star-Forming Galaxies: Insights from KBSS-MOSFIRE
• Collision Strengths for [O III] Optical and Infrared Lines
• Evidence for a Hard Ionizing Spectrum from a z=6.11 Stellar Population
• VLT/FLAMES high-resolution chemical abundances in Sculptor: a textbook dwarf spheroidal galaxy
• Fundamental Properties of O-Type Stars
• Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution
• An Ultraviolet Spectroscopic Atlas of Local Starbursts and Star-Forming Galaxies: The Legacy of FOS and GHRS
• The Column Density, Kinematics, and Thermal State of Metal-Bearing Gas within the Virial Radius of z~2 Star-Forming Galaxies in the Keck Baryonic Structure Survey
• Small Scale Structure at High Redshift: II. Physical Properties of the CIV Absorbing Clouds
• High Redshift Metals I.: The Decline of C IV at z > 5.3
• Massive stars at low metallicity: Evolution and surface abundances of O dwarfs in the SMC
• Young stars and ionized nebulae in M83: comparing chemical abundances at high metallicity
• Characterizing Extreme Emission Line Galaxies I: A Four-Zone Ionization Model for Very-High-Ionization Emission
• Cosmicflows-3: Two Distance$-$Velocity Calculators
• On the O/H, Mg/H, Si/H and Fe/H Gas and Dust Abundance Ratios in Galactic and Extragalactic H II Regions
• The [Fe IV] Discrepancy: Constraining the Iron Abundances in Nebulae
• The peculiar velocity field up to $z\sim 0.05$ by forward-modeling Cosmicflows-3 data
• The Impact of Starbursts on the Circumgalactic Medium
• The NIRVANDELS Survey: a robust detection of $\alpha$-enhancement in star-forming galaxies at $z\simeq 3.4$
• Intense CIV and HeII Emission in z~0 Galaxies: Probing High-Energy Ionizing Photons
• The MOSDEF-LRIS Survey: The Interplay Between Massive Stars and Ionized Gas in High-Redshift Star-Forming Galaxies
• Extremely metal-poor galaxies with HST/COS: laboratories for models of low-metallicity massive stars and high-redshift galaxies
• Extremely Metal-Poor Representatives Explored by the Subaru Survey (EMPRESS). I. A Successful Machine Learning Selection of Metal-Poor Galaxies and the Discovery of a Galaxy with M*<10^6 M_sun and 0.016 Z_sun
• Modelling ultraviolet-line diagnostics of stars, the ionized and the neutral interstellar medium in star-forming galaxies
• New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars. I. Method and first results
• Very Massive Stars: a metallicity-dependent upper-mass limit, slow winds, and the self-enrichment of Globular Clusters
• The extended HeII$\lambda$4686 emission in the extremely metal-poor galaxy SBS0335-052E seen with MUSE
• The MOSDEF-LRIS Survey: The Connection Between Massive Stars and Ionized Gas in Individual Galaxies at $z\sim 2$
• The Star Formation History of the very metal poor BCD IZw18 from HST/ACS data
• Heavy Element Absorption Systems at $5.0<z<6.8$: Metal-Poor Neutral Gas and a Diminishing Signature of Highly Ionized Circumgalactic Matter
• Strong Lyman continuum emitting galaxies show intense CIV 1550 emission
• The Grism Lens-Amplified Survey from Space (GLASS). XI. Detection of CIV in Multiple Images of $z=6.11$ Ly$\alpha$ Emitter Behind RXCJ2248.7-4431
• No breakdown of the radiatively-driven wind theory in low-metallicity environments
• Anatomy of a Young Massive Star Cluster: NGC 1569-B
• Chemical abundance scaling relations for multiple elements in z~2-3 star-forming galaxies
• Ultraviolet spectra of extreme nearby star-forming regions: evidence for an overabundance of very massive stars
• EMPRESS. IV. Extremely Metal-Poor Galaxies (EMPGs) Including Very Low-Mass Primordial Systems with M*=10^4--10^5 M_sun and 2--3% (O/H)_sun: High (Fe/O) Suggestive of Metal Enrichment by Hypernovae/Pair-Instability Supernovae
• Low-redshift lowest-metallicity star-forming galaxies in the SDSS DR14
• The MOSDEF Survey: A Comprehensive Analysis of the Rest-optical Emission-line Properties of $z\sim 2.3$ Star-forming Galaxies
• EMPRESS. II. Highly Fe-Enriched Metal-poor Galaxies with $\sim 1.0$ (Fe/O)${}_{\odot }$ and $0.02$ (O/H)${}_{\odot }$ : Possible Traces of Super Massive ($>300M_{\odot }$) Stars in Early Galaxies
• The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MEGaSaURA) II: Stacked Spectra
• Red Supergiants as cosmic abundance probes: the first direct metallicity determination of NGC 4038 in the Antennae
• Catastrophic Cooling in Superwinds: Line Emission and Non-equilibrium Ionization
• The Carina Project. VIII. The α-element abundances
• Atmospheric NLTE models for the spectroscopic analysis of blue stars with winds. V. Complete comoving frame transfer, and updated modeling of X-ray emission
• Stars and gas in the most metal-poor galaxies I: COS and MUSE observations of SBS 0335-052E
• Photometric identification and MMT spectroscopy of new extremely metal-poor galaxies: towards a better understanding of young stellar populations at low metallicity
• The First Metallicity Study of M83 using the integrated UV light of Star Clusters
• On the reliability of CIV 1549 as an abundance indicator for high redshift star-forming galaxies
• Chemical abundances of two extragalactic young massive clusters
• Big Bang Nucleosynthesis and the Helium Isotope Ratio
• Far-Ultraviolet Spectroscopy of Star-Forming Regions in Nearby Galaxies: Stellar Populations and Abundance Indicators
• Deciphering stellar metallicities in the early Universe: Case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field

Cited by in corpus (18)

• The GLASS James Webb Space Telescope Early Release Science Program. I. Survey Design and Release Plans
• SDSS-IV MaNGA: pyPipe3D analysis release for 10,000 galaxies
• Closing in on the sources of cosmic reionization: first results from the GLASS-JWST program
• CLASSY IV: Exploring UV diagnostics of the interstellar medium in local high-$z$ analogs at the dawn of the JWST era
• Early Results from GLASS-JWST. XXI: Rapid assembly of a galaxy at z=6.23 revealed by its C/O abundance
• JADES: The star-formation and chemical enrichment history of a luminous galaxy at z~9.43 probed by ultra-deep JWST/NIRSpec spectroscopy
• Nebular emission from young stellar populations including binary stars
• Inferring the HII region escape fraction of ionizing photons from infrared emission lines in metal-poor star-forming dwarf galaxies
• Spectral Shapes of the Lya Emission from Galaxies. II. the influence of stellar properties and nebular conditions on the emergent Lya profiles
• Spatially-resolved chemodynamics of the starburst dwarf galaxy CGCG 007-025: Evidence for recent accretion of metal-poor gas
• Insights into the reionization epoch from cosmic-noon-CIV emitters in the VANDELS survey
• Trading oxygen for iron I: the [O/Fe] -- specific star formation rate relation of galaxies
• Nuclear Activity in the Low Metallicity Dwarf Galaxy SDSS J0944-0038: A Glimpse into the Primordial Universe
• Extremely strong CIV 1550 nebular emission in the extremely low-metallicity star-forming galaxy J2229+2725
• Testing SALT Approximations with Numerical Radiation Transfer Code Part 1: Validity and Applicability
• Nebular C IV 1550 Imaging of the Metal-Poor Starburst Mrk 71: Direct Evidence of Catastrophic Cooling
• Monitoring broad emission-line components in spectra of the two low-metallicity dwarf compact star-forming galaxies SBS 1420+540 and J1444+4840
• Shocks and complex chemodynamics in the metal-poor starburst galaxy CGCG 007-025 revealed through high-resolution echelle spectroscopy