Early Results from GLASS-JWST. XXV. Electron Density in the Interstellar Medium at 0.7 ≲ z ≲ 9.3 with NIRSpec High-resolution Spectroscopy*
Sijia Li, Xin Wang, Yuguang Chen, Tucker Jones, Tommaso Treu, Karl Glazebrook, Xianlong He, Alaina Henry, Xiao-Lei Meng, Takahiro Morishita, Guido Roberts-Borsani, Lilan Yang, Hao-Ran Yu, Antonello Calabrò, M. Castellano, Nicha Leethochawalit, Benjamin Metha, Themiya Nanayakkara, Namrata Roy, Benedetta Vulcani
Abstract
Abstract The electron density ( n e ) of the interstellar medium (ISM) in star-forming galaxies is intimately linked to star formation and ionization condition. Using the high-resolution spectra obtained from the JWST Near-Infrared Spectrograph (NIRSpec) microshutter assembly (MSA) as part of the GLASS-JWST program, we have assembled the largest sample to date (34 galaxies) with individual n e measurements derived from the [O ii ] λλ 3726, 29 and/or [S ii ] λλ 6718, 32 doublets at 0.7 ≲ z ≲ 9.3. The gravitational lensing magnification by the foreground A2744 cluster allows us to probe n e in galaxies with stellar masses ( M * ) down to ≃10 7.5 M ⊙ across the entire redshift range. Our analysis reveals that the [O ii ] flux ratios are marginally anticorrelated with a specific star formation rate (sSFR) within a 1 σ confidence interval, whereas the [S ii ] flux ratios show no significant correlation with sSFR. Despite a clear correlation between sSFR and redshift within our sample, we find no apparent redshift evolution of n e at z ≃ 1–9. Our data set also includes 13 galaxies where n e can be measured from both [O ii ] and [S ii ]. Contrary to findings at lower redshifts, we observe considerable scatter in n e measurements from [O ii ] and [S ii ], indicating a complex gaseous environment with significant variations in n e in high-redshift galaxies. This work highlights the unique capability of JWST NIRSpec/MSA high-resolution spectroscopy to characterize the detailed physical properties of the ISM in individual high-redshift galaxies.