Evidence of strong quasar feedback in the early Universe

Most theoretical models invoke quasar driven outflows to quench star formation in massive galaxies, and this feedback mechanism is required to account for the population of old and passive galaxies observed in the local universe. The discovery of massive, old and passive galaxies at z∼2, implies that such quasar feedback onto the host galaxymust have been at work very early on, close to the reionization epoch. We have observed the [CII]158μm transition in SDSSJ114816.64+525150.3 that, at z=6.4189, is one of the most distant quasars known. We detect broad wings of the line tracing a quasar-driven massive outflow. This is the most distant massive outflow ever detected and is likely tracing the long sought quasar feedback, already at work in the early Universe. The outflow is marginally resolved on scales of ∼16 kpc, implying that the outflow can really affect the whole galaxy, as required by quasar feedback models. The inferred outflow rate, ˙M > 3500 M⊙ yr−1, is the highest ever found. At this rate the outflow can clean the gas in the host galaxy, and therefore quench star formation, in a few million years.