2025/02/09 by K. E. Heintz, Heintz, Kasper E., Joris Witstok +14 · 3 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2502.06016
openalex publication_date 2025/02/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
At cosmic dawn, the first stars and galaxies are believed to form from and be deeply embedded in clouds of dense, pristine gas. Here we present a study of the JWST/NIRSpec data of the most distant, spectroscopically confirmed galaxy observed to date, JADES-GS-z14-0 (GS-z14 for short), at z=14.179, combined with recent far-infrared measurements of the [OIII]-88μm and [CII]-158μm line transitions and underlying dust-continuum emission. Based on the observed prominent damped Lyman-α (DLA) absorption profile, we determine a substantial neutral atomic hydrogen (HI) column density, log (N\rm HI / \rm cm-2) = 22.27+0.08-0.09, consistent with previous estimates though seemingly at odds with the dynamical and gas mass of the galaxy. Using various independent but complementary approaches, considering the implied neutral gas mass from the DLA measurement, the star-formation rate surface density, and the metal abundance, we demonstrate that the total gas mass of GS-z14 is of the order log (M\rm gas / M_\odot) = 9.8± 0.3. This implies a substantial gas mass fraction, f\rm gas \gtrsim 0.9 and that the bulk of the interstellar medium (ISM) is in the form of HI. We show that the derived gas mass is fully consistent with the non-detection of [CII]-158μm, assuming an appropriate scaling to the neutral gas. The low dust-to-gas ratio, AV/N\rm HI = (1.3± 0.6)× 10-23 mag cm2, derived in the line-of-sight through the DLA further indicates that the absorbing gas is more pristine than the central, star-forming regions probed by the [OIII]-88μm emission. These results highlight the implications for far-infrared line-detection searchers attainable with ALMA and demonstrate that the bright, relatively massive galaxy GS-z14 at z=14.179 is deeply embedded in a substantial, pristine HI gas reservoir dominating its baryonic matter content.