Paper: JWST and ALMA Joint Analysis with [O II] λλ3726, 3729, [O III] λ4363, [O III] 88 μm, and [O III] 52 μm: Multizone Evolution of Electron Densities at z ∼ 0–14 and its Impact on Metallicity Measurements
Authors: Yuichi Harikane, Ryan L. Sanders, Richard Ellis, Tucker Jones, Masami Ouchi, Nicolas Laporte, Guido Roberts-Borsani, Harley Katz, Kimihiko Nakajima, Yoshiaki Ono, Mansi Gupta
Figure caption: Redshift evolution of electron densities. The red, blue, and purple symbols represent electron densities measured using the FIR [O III] emission line, optical [O II] λλ3726, 3729 or [S II] λλ6716, 6731 emission lines, and UV C III] λ1907, 1909 emission lines, respectively. We find that the electron densities measured with the FIR [O III] emission line are typically ∼100 cm−3, regardless of redshift. In contrast, densities measured with the optical lines increase toward higher redshifts. The densities measured with the UV C III] λ1907, 1909 lines are higher than 1000 cm−3 and exceed those measured with the optical lines at fixed redshift. The red small diamonds represent our individual measurements for the three galaxies from the [O III] 52 μm/[O III] 88 μm ratio and the red large diamond represents the median of these measurements. The red small square and circle represent densities measured for A1689-zD1 at z = 7.1 (M. Killi et al. 2023) and GHZ2 at z = 12.3 (J. A. Zavala et al. 2024), respectively. The red up-pointing and right-pointing triangles represent the median densities of galaxies at z ∼ 0 measured using the [O III] 52 μm/[O III] 88 μm ratio in J. A. Fernández-Ontiveros et al. (2016) and J. R. Brauher et al. (2008), respectively. The red small open squares represent measurements from the [O III] 88 μm/[O III] λ5007 ratio for COS-3018555981 at z = 6.9 (J. Witstok et al. 2022; J. Scholtz et al. 2025), MACS0416-Y1 at z = 8.3 (A. Harshan et al. 2024), ID4590 at z = 8.5 (S. Fujimoto et al. 2024), MACS1149-JD1 at z = 9.1 (M. Stiavelli et al. 2023), and JADES-GS-z14-0 at z = 14.2 (S. Carniani et al. 2025; S. Schouws et al. 2025). The blue small diamonds represent our individual measurements from the [O II] λ3729/[O II] λ3726 ratio, and the blue large diamond represents the median of them. Densities measured with the [O II] λ3729/[O II] λ3726 or [S II] λ6716/[S II] λ6731 ratios from the literature are shown with the blue symbols (Y. Isobe et al. 2023, star; M. W. Topping et al. 2025, circle; R. L. Sanders et al. 2016, up-pointing triangle; R. L. Davies et al. 2021, down-pointing triangle; D. Kashino et al. 2017, left-pointing triangle; M. Mingozzi et al. 2022, pentagon; and J. Moustakas & R. C. Kennicutt 2006, right-pointing triangle). The blue small squares represent measurements for COS-3018555981 at z = 6.9 (J. Scholtz et al. 2025), MACS1149-JD1 at z = 9.1 (C. Marconcini et al. 2024), and MACS0647-JD at z = 10.2 (Abdurro’uf et al. 2024). The purple small circles represent measurements from the [C III] λ1907/C III] λ1909 ratio in M. W. Topping et al. (2025), and the purple large circle represents their average. The purple up-pointing triangle and pentagon are measurements from M. V. Maseda et al. (2017) and M. Mingozzi et al. (2022), respectively, while the purple small square and down-pointing triangle represent densities for GN-z11 at z = 10.6 (Y. Xu et al. 2024) and for EGS-zs8-1 at z = 7.7 (D. P. Stark et al. 2017), respectively.