Nature Astronomy abstract of study findings:
Models predict that chemical enrichment and gas redistribution should begin rapidly once star formation starts, but direct constraints at the earliest epochs have been scarce. Here we show that metal-enriched gas in multiple ionic phases was already present around galaxies before the midpoint of cosmic reionization. Using JWST/NIRSpec rest-frame ultraviolet spectroscopy from SPURS, we detect blueshifted metal absorption in three galaxies at 7.2 < z < 9.3. The detected transitions span neutral, low-ionization and high-ionization species, including O I, Si II, C II, Si IV and C IV, with velocity offsets of ∣Δv∣ ≈ 50–250 km s−1 relative to nebular systemic redshifts. The ionic coexistence, overlapping velocity structure and equivalent-width ratios are consistent with outflowing or otherwise kinematically disturbed galaxy-associated gas, implying rapid metal enrichment. These results show that key conditions for baryon cycling were established in at least a subset of luminous galaxies within the first several hundred million years of cosmic time, well before the completion of reionization.
Citation: Zhu, Y., Ji, Z., Becker, G.D. et al. Early metal-enriched baryon cycling before the midpoint of cosmic reionization. Nat Astron (2026).
DOI: https://doi.org/10.1038/s41550-026-02988-2
Study-related stories:
EurekAlert! – “JWST Finds Early Galaxies Were Already Seeding the Universe with Heavy Elements”
Cornell Chronicle – “Astronomers Discover Metal-rich Galaxies in Early Universe”
Astro Current – “JWST Finds Early Galaxies Seeded the Infant Universe with Heavy Elements”
