Electron density in the O+ ionization zone

Determine the electron density in the O+ ionization zone of C3PO-84478, which cannot be directly measured because the [O II] doublet is not detected.

Background

The analysis derives the electron density in the C2+ zone from the C III] λλ1907,1909 flux ratio, but the electron density in the O+ zone would ordinarily be constrained using the [O II] λλ3727,3729 doublet. Because that doublet is undetected in the JWST NIRSpec spectrum of C3PO-84478, the O+-zone density remains unresolved. Determining it would improve the characterization of the galaxy’s ionized gas and the reliability of abundance and ionization diagnostics.

References

Due to the non-detection of the O\ doublet in C3PO-84478\, we are unable to directly measure the electron density in the O${+}$ zone.

— C3PO: A Lyα Emitting Galaxy at $z \sim 9$  (2609.03608 - Hu et al., 3 Sep 2026) in Section 3.4, “ISM Properties,” subsection “Electron temperature and density”