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Large-scale outflows driven by supermassive black holes are thought to have a fundamental role in suppressing star formation in massive galaxies. However, direct observational evidence for this hypothesis is still lacking, particularly in the young universe where star-formation quenching is remarkably rapid1–3, thus requiring effective removal of gas4 as opposed to slow gas heating5,6. Although outflows of ionized gas are frequently detected in massive distant galaxies7, the amount of ejected mass is too small to be able to suppress star formation8,9. Gas ejection is expected to be more efficient in the neutral and molecular phases10, but at high redshift these have only been observed in starbursts and quasars11,12. Here we report JWST spectroscopy of a massive galaxy experiencing rapid quenching at a redshift of 2.445. We detect a weak outflow of ionized gas and a powerful outflow of neutral gas, with a mass outflow rate that is sufficient to quench the star formation. Neither X-ray nor radio activity is detected; however, the presence of a supermassive black hole is suggested by the properties of the ionized gas emission lines. We thus conclude that supermassive black holes are able to rapidly suppress star formation in massive galaxies by efficiently ejecting neutral gas.JWST observations of a massive galaxy at a redshift of 2.45 show a powerful outflow of neutral gas, with a mass outflow rate that is sufficient to shut down star formation. [ABSTRACT FROM AUTHOR]

Stellar archaeology shows that massive elliptical galaxies formed rapidly about ten billion years ago with star-formation rates of above several hundred solar masses per year. Their progenitors are probably the submillimetre bright galaxies at redshifts z greater than 2. Although the mean molecular gas mass (5 × 1010 solar masses) of the submillimetre bright galaxies can explain the formation of typical elliptical galaxies, it is inadequate to form elliptical galaxies that already have stellar masses above 2 × 1011 solar masses at z ≈ 2. Here we report multi-wavelength high-resolution observations of a rare merger of two massive submillimetre bright galaxies at z = 2.3. The system is seen to be forming stars at a rate of 2,000 solar masses per year. The star-formation efficiency is an order of magnitude greater than that of normal galaxies, so the gas reservoir will be exhausted and star formation will be quenched in only around 200 million years. At a projected separation of 19 kiloparsecs, the two massive starbursts are about to merge and form a passive elliptical galaxy with a stellar mass of about 4 × 1011 solar masses. We conclude that gas-rich major galaxy mergers with intense star formation can form the most massive elliptical galaxies by z ≈ 1.5. [ABSTRACT FROM AUTHOR]

HXMM01 (1HERMES S250 J022016.5-060143) was identified as an unusually bright submillimetre bright galaxy (SMG) (5) in the Herschel Multi-tiered Extragalactic Survey (HerMES6). We observed it with a variety of ground-based [...], Stellar archaeology (1) shows that massive elliptical galaxies formed rapidly about ten billion years ago with star-formation rates of above several hundred solar masses per year. Their progenitors are probably the submillimetre bright galaxies (2) at redshifts z greater than 2. Although the mean molecular gas mass (3) (5 X 1010 solar masses) of the submillimetre bright galaxies can explain the formation of typical elliptical galaxies, it is inadequate to form elliptical galaxies (4) that already have stellar masses above 2 X [10.sup.11] solar masses at z ≅ 2. Here we report multi-wavelength high-resolution observations of a rare merger of two massive submillimetre bright galaxies at z = 2.3. The system is seen to be forming stars at a rate of 2,000 solar masses per year. The star-formation efficiency is an order of magnitude greater than that of normal galaxies, so the gas reservoir will be exhausted and star formation will be quenched in only around 200 million years. At a projected separation of 19 kiloparsecs, the two massive starbursts are about to merge and form a passive elliptical galaxy with a stellar mass of about 4 X [10.sup.11] solar masses. We conclude that gas-rich major galaxy mergers with intense star formation can form the most massive elliptical galaxies by z [approximately equal to] 1.5.