Quasar outflows in the young Universe

A study led by Manuela Bischetti, Chiara Feruglio e Valentina D'Odorico of the INAF Astronomical Observatory of Trieste, has measured for the first time the fraction of winds produced by supermassive black holes at the centre of galaxies in the primordial Universe, revealing how such winds were much more frequent and powerful at the time than those observed in galaxies that are closer to us. This could explain the mechanism that halted the growth of supermassive black holes across the history of the cosmos. These results have been published in the journal Nature.

The work is based on observations of 30 quasars – extremely bright, point-like sources at the core of distant galaxies, whose emission arises from the intense activity of the central supermassive black holes sucking in the surrounding matter – obtained with the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile. The host galaxies of these quasars were observed around cosmic dawn, when the Universe was between 500 million and one billion years old.
“For the first time, we measured the fraction of quasars in the young Universe exhibiting black hole winds”, says Manuela Bischetti, INAF researcher in Trieste and first author of the new study. “Unlike what we observe in the Universe that is closer to us, we discovered that black hole winds in the young Universe are very frequent, have high speeds, up to 17% of the speed of light, and inject large amounts of energy into their host galaxy”.
half of the quasars observed in this research show black hole winds, which are therefore much more frequent than the ones known in the quasars of the more nearby cosmos – when the Universe was around four billion years old – besides being 20 times more powerful. The energy injected by winds would have been thus able to halt further matter accretion onto the black hole, slowing down its growth and kicking off a ‘common evolution’ phase between the black hole and its host galaxy.
A totally unexpected discovery, it was made possible by the high quality data from the X-shooter instrument installed on the VLT, in the context of a large ESO programme with around 250 hours of observations.
“Quasars are among the brightest objects observable in the early Universe, but due to their distance they are quite faint in terms of observed magnitude”, explains co-author Valentina D’Odorico from INAF in Trieste, affiliated to Scuola Normale Superiore in Pisa and principal investigator of the observing programme the study is based upon. “The large investment of time dedicated to observing these objects and the unique capacities of X-shooter in terms of efficiency, wavelength coverage and resolving power have allowed us to obtain very good quality spectra which enabled this interesting result”.

The article “Suppression of black-hole growth by strong outflows at redshifts 5.8-6.6”, di Bischetti M., Feruglio C., D’Odorico V., et al., Nature 605-244-247 https://www.nature.com/articles/s41586-022-04608-1



The researchers Valentina D’Odorico (left), Manuela Bischetti (center) and Chiara Feruglio (right). Credits: Inaf