2025A&A...696A..87C

JADES-GS-z14-0 is the most distant spectroscopically confirmed galaxy yet, at z≳14. With a UV magnitude of -20.81, it is one of the most luminous galaxies at cosmic dawn and its half-light radius of 260 pc means that stars dominate the observed UV emission. We report the Atacama Large Millimeter/submillimeter Array (ALMA) detection of [O III]88 μm line emission with a significance of 6.67σ and at a frequency of 223.524 GHz, corresponding to a redshift of 14.1796±0.0007, which is consistent with the candidate C III] line detected in the NIRSpec spectrum. At this spectroscopic redshift, the Lyman-α break identified with NIRSpec requires a damped Lyman-α absorber with a column density of log(N_HI/cm^–2) = 21.96. The total [O III]88 μm luminosity (log(L_[OIII]/L_⊙) = 8.3±0.1) is fully consistent with the local L_[OIII]-SFR relation and indicating a gas-phase metallicity >0.1 Z_⊙. Using prospector spectral energy distribution (SED) modeling and combining the ALMA data with JWST observations, we find Z = 0.17 Z_⊙ and a non-zero escape fraction of ionizing photons (∼11%), which is necessary by the code to reproduce the UV spectrum. We measure an [OIII]5007 Å/[OIII]88 μm line flux ratio between 1 and 20, resulting in an upper limit to the electron density of roughly 700 cm^–3 assuming a single-cloud photoionization model. The [O III]emission line is spectrally resolved, with a FWHM of 102$ {}^{+29}_{-22}\, $km s^–1, resulting in a dynamical mass of log(M_dyn/M_⊙) = 9.0±0.2. When compared to the stellar mass, this value represents a conservative upper limit on the gas mass fraction, which ranges from 50% to 80%, depending on the assumed star formation history. Past radiation-driven outflows may have cleared the galaxy from the gas, reducing the gas fraction and thus increasing the escape fraction of ionizing photons.