The eventful life of a luminous galaxy at z = 14: metal enrichment, feedback, and low gas fraction?

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 6.67 σ 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 OIII5007 Å/OIII88 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 −22 +29 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.