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 examine the factors responsible for variation in ionization parameter ( U ) of high-redshift star-forming galaxies based on medium-resolution JWST/NIRSpec observations obtained by Cosmic Evolution Early Release Science survey. The sample consists 48 with redshifts z spec = 2.7−6.3, which are largely representative typical at these redshifts. [S ii ] λ 6718, 6733 doublet is used to estimate electron densities n e ), and dust-corrected H α luminosities compute ionizing photon rates Q ). Using composite spectra bins [O iii 4960, 5008/[O 3727, 3730 (O32) as a proxy , we determine that higher O32 have 〈 〉 ≃ 500 cm −3 ≳5 × larger than lower-O32 galaxies. do not find significant difference between low- high-O32 Photoionization modeling indicates large spread log U ≈1.5 dex fixed Z neb . On other hand, data indicate highly correlation star-formation-rate surface density (Σ SFR appears be redshift invariant ∼ 1.6−6.3, possibly up 9.5. consider several avenues through metallicity Σ (or gas density) may influence including variations internal dust extinction photons, effects volume filling fraction. Based considerations, conclude play more central role modulating