Routing protocol

Physics

Meteorology

Supermassive black hole

Computer network

Active galactic nucleus

Black hole (networking)

Outflow

Link-state routing protocol

Galaxy

Stellar black hole

Astronomy

Quasar

Accretion (finance)

Gravitational wave

Computer science

Astrophysics

Routing (electronic design automation)

Binary black hole

Redshift

Reionization

Universe

Nature

Bright quasars, powered by accretion onto billion-solar-mass black holes, already existed at the epoch of reionization, when the Universe was 0.5–1 billion years old1. How these black holes formed in such a short time is the subject of debate, particularly as they lie above the correlation between black-hole mass and galaxy dynamical mass2,3 in the local Universe. What slowed down black-hole growth, leading towards the symbiotic growth observed in the local Universe, and when this process started, has hitherto not been known, although black-hole feedback is a likely driver4. Here we report optical and near-infrared observations of a sample of quasars at redshifts 5.8 ≲ z ≲ 6.6. About half of the quasar spectra reveal broad, blueshifted absorption line troughs, tracing black-hole-driven winds with extreme outflow velocities, up to 17% of the speed of light. The fraction of quasars with such outflow winds at z ≳ 5.8 is ≈2.4 times higher than at z ≈ 2–4. We infer that outflows at z ≳ 5.8 inject large amounts of energy into the interstellar medium and suppress nuclear gas accretion, slowing down black-hole growth. The outflow phase may then mark the beginning of substantial black-hole feedback. The red optical colours of outflow quasars at z ≳ 5.8 indeed suggest that these systems are dusty and may be caught during an initial quenching phase of obscured accretion5. A study reporting optical and near-infrared observations of quasars at redshifts 5.8–6.6 shows that&nbsp;about half have strong winds, up to 17% the speed of light, suppressing black-hole growth.

Suppression of black-hole growth by strong outflows at redshifts 5.8–6.6