2025/04/03 by Romain A. Meyer, R. A. Meyer, Meyer, Romain A. +8 · 1 voice
Physics and Astronomy · #Adaptive optics and wavefront sensing #Astronomy and Astrophysical Research #Radio Astronomy Observations and Technology
paper · pdf · doi:10.1093/mnras/staf1312
ABSTRACT We present the first characterization of the Gunn–Peterson trough in high-redshift galaxies using public James Webb Space Telescope (JWST) NIRSpec spectroscopy. This enables us to derive the first galaxy-based intergalactic medium (IGM) opacity measurements at the end of reionization. Using galaxy spectra has several advantages over quasar spectra: it enables measurements of the IGM opacity in any extragalactic field over a continuous redshift range 4\lesssim z\lesssim 7, as well as measurements of the intrinsic Lyman β opacity. Our novel constraints are in good agreement with state-of-the-art ground-based quasar Lyman α forest observations, and will become competitive as the number of JWST z>5 galaxy spectra rapidly increases. We also provide the first constraints on the uncontaminated Lyman β opacity at 5 \lt z \lt 6. Finally, we demonstrate the power of JWST to connect the ionization state of the IGM to the sources of reionization in a single extragalactic field. We show that a previously reported galaxy overdensity and an excess of Lyman α emitters detected with JWST in GOODS-South at z=5.8 - 5.9 coincides with an anomalously low IGM opacity to Lyman α at this redshift. The local photoionization rate excess can be fully accounted for by the cumulative ionizing output of M_\rm UV\lesssim -10 galaxies in the overdensity, provided they have log 10⟨ ξ _\rm ion f_\rm esc / [\rm erg-1\rm Hz]⟩ ≃ 25 (e.g. log 10ξ _\rm ion / [\rm erg-1\rm Hz]=25.4 and f_\rm esc=40~ \rm per cent). Overall, this breakthrough offers a new way to connect the galaxy large-scale structure to the state of the IGM, potentially enabling us to precisely identify the sources of reionization.