A JWST/NIRSpec Exploration of the Connection between Ionization Parameter, Electron Density, and Star-Formation-Rate Surface Density in z=2.7-6.3 Galaxies

Abstract

We conduct a statistical analysis of the factors responsible for the variation in the ionization parameter (U) of high-redshift star-forming galaxies based on medium resolution JWST/NIRSpec observations obtained by the Cosmic Evolution Early Release Science (CEERS) survey. The sample consists of 48 galaxies with spectroscopic redshifts z=2.7-6.3 which are largely representative of typical star-forming galaxies at these redshifts. The [SII] 6718, 6733 doublet is used to estimate electron densities (n_e), and dust-corrected Ha luminosities are used to compute total ionizing photon rates (Q). Using composite spectra of galaxies in bins of [OIII]/[OII] (i.e., O32) as a proxy for U, we determine that galaxies with higher O32 have <n_e> ~ 500 cm^-3 that are at least a factor of ~5 larger than that of lower-O32 galaxies. We do not find a significant difference in <Q> between low- and high-O32 galaxies. Photoionization modeling of all available strong rest-frame optical emission lines is used to simultaneously constrain U and oxygen abundance (Z_neb). We find a large spread in log U of ~1.5 dex at a fixed Z_neb. On the other hand, the data indicate a highly significant correlation between U and star-formation-rate surface density (Sigma_SFR) which appears to be redshift invariant at z~1.6-6.3, and possibly up to z~9.5. We consider several avenues through which metallicity and Sigma_SFR (or gas density) may influence U, including variations in n_e and Q that are tied to metallicity and gas density, internal dust extinction of ionizing photons, and the effects of gas density on the volume filling fraction of dense clumps in HII regions and the escape fraction of ionizing photons. Based on these considerations, we conclude that gas density may play a more central role than metallicity in modulating U at these redshifts.

16 pages, 13 figures, 4 tables

References in corpus (35)

• 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
• Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample
• An ultra-deep near-infrared spectrum of a compact quiescent galaxy at z=2.2
• Pre-Supernova Evolution of Massive Single and Binary Stars
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• The Dynamics of Radiation Pressure-Dominated HII Regions
• 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
• Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: IV The Controlling Parameters of the Starburst SED
• New insights into the stellar content and physical conditions of star-forming galaxies at z = 2-3 from spectral modelling
• Deriving model-based T${}_e$-consistent chemical abundances in ionised gaseous nebulae
• GOODS-HERSCHEL: star formation, dust attenuation and the FIR-radio correlation on the Main Sequence of star-forming galaxies up to z~4
• Metallicities and Physical Conditions in Star-forming Galaxies at z~1.0-1.5
• Ultraviolet spectra of extreme nearby star-forming regions --- approaching a local reference sample for JWST
• Geometry of Star-Forming Galaxies from SDSS, 3D-HST and CANDELS
• Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: II. Control of the \HII Region Parameters
• Revisiting the Integrated Star Formation Law. II. Starbursts and the Combined Global Schmidt Law
• X-ray binaries as the origin of nebular HeII emission in low-metallicity star-forming galaxies
• The MOSDEF Survey: the Variation of the Dust Attenuation Curve with Metallicity
• The VANDELS survey: the stellar metallicities of star-forming galaxies at 2.5 < z < 5.0
• Understanding the escape of LyC and Ly$\alpha$ photons from turbulent clouds
• Neon and Argon optical emission lines in ionized gaseous nebulae: Implications and applications
• The COSMOS [OII] Survey: Evolution of Electron Density with Star Formation Rate
• SDSS-IV MaNGA: What Shapes The Distribution Of Metals In Galaxies? Exploring The Roles Of The Local Gas Fraction And Escape Velocity
• On the importance of using appropriate spectral models to derive physical properties of galaxies at 0.7<z<2.8
• Investigating H$\alpha$, UV, and IR star-formation rate diagnostics for a large sample of z ~ 2 galaxies
• The MOSDEF-LRIS Survey: The Connection Between Massive Stars and Ionized Gas in Individual Galaxies at $z\sim 2$
• Exploring HeII$\lambda$1640 emission line properties at $z\sim 2-4$
• Paschen-line Constraints on Dust Attenuation and Star Formation at z~1-3 with JWST/NIRSpec
• The KMOS${}^{3D}$ Survey: Investigating the Origin of the Elevated Electron Densities in Star-Forming Galaxies at $1\lesssim z\lesssim 3$
• JWST/NIRSpec Measurements of the Relationships Between Nebular Emission-line Ratios and Stellar Mass at z~3-6
• The growth of H II regions around massive stars: the role of metallicity and dust
• Disentangling the physical parameters of gaseous nebulae and galaxies
• Physics of Prodigious Lyman Continuum Leakers
• Lyman-Alpha Escape from Low-Mass, Compact, High-Redshift Galaxies

Cited by in corpus (31)

• JADES: Detecting [OIII]$\lambda 4363$ Emitters and Testing Strong Line Calibrations in the High-$z$ Universe with Ultra-deep JWST/NIRSpec Spectroscopy up to $z\sim 9.5$
• JADES: Carbon enrichment 350 Myr after the Big Bang in a gas-rich galaxy
• A luminous and young galaxy at z=12.33 revealed by a JWST/MIRI detection of Hα and [OIII]
• The UNCOVER Survey: A First-look HST+JWST Catalog of Galaxy Redshifts and Stellar Population Properties Spanning $0.2\lesssim z\lesssim 15$
• JADES: The star-formation and chemical enrichment history of a luminous galaxy at z~9.43 probed by ultra-deep JWST/NIRSpec spectroscopy
• Dust attenuation evolution in $z\sim 2$-$12$ JWST galaxies
• Ionized gas kinematics and chemical abundances of low-mass star-forming galaxies at $z\sim 3$
• GA-NIFS: Multi-phase analysis of a star-forming galaxy at $z\sim 5.5$
• The evolution of the SFR and Sigma-SFR of galaxies in cosmic morning (4 < z < 10)
• Anatomy of a z=6 Lyman-α emitter down to parsec scales: extreme UV slopes, metal-poor regions and possibly leaking star clusters
• A quasar-galaxy merger at $z\sim 6.2$: rapid host growth via accretion of two massive satellite galaxies
• GA-NIFS: JWST/NIRSpec IFS view of the z~3.5 galaxy GS5001 and its close environment at the core of a large-scale overdensity
• The density-bounded twilight of starbursts in the early Universe
• Extreme Ionizing Properties of Metal-Poor, Muv ~ -12 Star Complex in the first Gyr
• The GLASS-JWST Early Release Science Program. IV. Data release of 263 spectra from 245 unique sources
• Early Results from GLASS-JWST. XXV. Electron Density in the Interstellar Medium at $0.7\lesssim z\lesssim 9.3$ with NIRSpec High-resolution Spectroscopy
• Evolution of the UV slope of galaxies at cosmic morning (z > 4): the properties of extremely blue galaxies
• Feedback and dynamical masses in high-$z$ galaxies: the advent of high-resolution NIRSpec spectroscopy
• Detection of the 2175Å UV Bump at z>7: Evidence for Rapid Dust Evolution in a Merging Reionisation-Era Galaxy
• Exploring Spatially-Resolved Metallicities, Dynamics and Outflows in Low-Mass Galaxies at $z\sim 7.6$
• NGDEEP: The Star Formation and Ionization Properties of Galaxies at $1.7<z<3.4$
• The JWST Emission Line Survey (JELS): Extending rest-optical narrow-band emission line selection into the Epoch of Reionization
• Physical properties of strong 1 < z < 3 Balmer and Paschen lines emitters observed with JWST
• Insights on Metal Enrichment and Environmental Effect at $z\approx 5-7$ with JWST ASPIRE/EIGER and Chemical Evolution Model
• The JWST/AURORA Survey: Multiple Balmer and Paschen Emission Lines for Individual Star-forming Galaxies at z=1.5-4.4. I. A Diversity of Nebular Attenuation Curves and Evidence for Non-Unity Dust Covering Fractions
• Cloudy-Maraston: Integrating nebular continuum and line emission with the Maraston stellar population synthesis models
• Reionization in Protocluster Environments at $z>7$ with JWST/NIRSpec
• The Cliff: A Metal-Poor Little Red Dot Hosting an Overmassive Black Hole at $z=3.55$
• Recovering the properties of the interstellar medium through integrated spectroscopy: application to the z~0 ECO volume-limited star-forming galaxy sample
• Unraveling the Lyman Continuum Emission of Ion3: Insights from HST multi-band imaging and X-Shooter spectroscopy
• The Cosmic Rush Hour: Rapid Formation of Bright, Massive, Disky, Star-Forming Galaxies as Signatures of Early-Universe Physics