JWST Finds Signs of Gas Cycling Around Three Galaxies From the Universe’s First Billion Years, With Oxygen and Carbon

Astronomers using the James Webb Space Telescope (JWST) found gas that holds oxygen, carbon and silicon around three distant galaxies. The light left these galaxies when the universe was less than a billion years old, before cosmic reionization reached its midpoint. The authors conclude that the conditions for gas cycling in and out of galaxies existed in at least some luminous galaxies within the first several hundred million years. The study appears in Nature Astronomy and is open access.

Three galaxies, one spectrum each

Yongda Zhu and colleagues used JWST’s NIRSpec instrument in the SPURS program, which observed the Abell 2744 field. The three galaxies sit at redshifts between 7.2 and 9.3, and each shows a bright continuum in its ultraviolet light. The team recorded their spectra across about 1 to 5 micrometers, with total exposure times of up to 29.2 hours.

What the spectra show

Each galaxy shows absorption lines from heavy elements, which astronomers call metals. The lines come from neutral oxygen, from low-ionization silicon and carbon, and from high-ionization silicon and carbon. All of them sit slightly blueward of the galaxies’ own systemic redshift, with velocity offsets of about 50 to 250 km/s. The high-ionization gas moves faster than the neutral and low-ionization gas by roughly 60 to 210 km/s, depending on the galaxy. The galaxies themselves hold stellar masses of roughly 1 to 6 billion times the Sun’s mass.

The authors say these features show that metal-enriched gas in several ionization phases already surrounded galaxies before the midpoint of reionization, which they place at redshift 7 to 8.

What the study cannot show

The sample holds only three UV-bright galaxies, so the results may not apply to galaxies in general. The spectra have a resolution of about 1,000, which is too coarse to separate individual gas components. The velocities alone cannot tell compact outflows apart from larger gas around the galaxy. The authors treat their column densities as conservative lower limits and use their ionization modeling only as qualitative guidance. They found no clear sign of an active black hole, but a weak or obscured one is not fully excluded. The study does not directly constrain the sources or the timing of reionization.

Source: Zhu, Y. et al., “Early metal-enriched baryon cycling before the midpoint of cosmic reionization,” Nature Astronomy (published 24 September 2026), DOI 10.1038/s41550-026-02988-2.