Black hole winds aren’t what they used to be

Black hole winds aren’t what they used to be


Artist’s rendering of the environment surrounding a supermassive black hole at the center of an active galaxy. Credit: ESO/M. grain knife

In the first billion years of the universe, winds blown by supermassive black holes at the centers of galaxies were much more frequent and stronger than those observed in present-day galaxies some 13 billion years later. Such winds were so powerful that they slowed the growth of the supermassive black holes from which they originate. These are the findings of a study led by three researchers from Italy’s National Institute for Astrophysics (INAF) in Trieste, published today in the journal Nature.

The work is based on the observations of 30 quasars observed with the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile. Quasars are extremely bright, point sources in the cores of distant galaxies, whose emission arises from the intense activity of central supermassive black holes sucking in surrounding matter. The host galaxies of these quasars were observed around cosmic dawn, when the Universe was between 500 million and 1 billion years old.

“For the first time we have measured the proportion of quasars in the young universe that exhibit winds from black holes,” says Manuela Bischetti, INAF researcher in Trieste and first author of the new study. “Contrary to what we observe in the nearby Universe, we have discovered that black hole winds are very common in the young Universe, have high velocities of up to 17 percent the speed of light, and inject large amounts of energy into their host galaxy. “

About half of the quasars observed in this research exhibit black-hole winds, which are much more common and 20 times stronger than those known in the quasars of the nearer cosmos when the Universe was about 4 billion years old.

“Observations of black holes in the young universe show that they grow much faster than their host galaxies, while in the local universe we know that black holes and galaxies co-evolve,” adds co-author Chiara Feruglio, INAF researcher in Trieste . “This implies that at some point in the universe some mechanism slowing the growth of black holes must have been at work. Our observations allowed us to identify this mechanism in the winds of black holes created when the Universe was 0.5 to 1 billion years old.”

The energy injected by winds would thus have been able to stop the further accumulation of matter onto the black hole, slowing its growth and initiating a phase of “co-evolution” between the black hole and its host galaxy. “This study allowed us to identify the epoch in the history of the Universe when the effects of black hole winds became significant,” adds Bischetti. “This has an enormous impact on our knowledge of the early stages of growth of black holes and their host galaxies, and severely limits the models describing the formation of the first galaxies.”

A totally unexpected discovery, made possible by the high-quality data from the Xshooter instrument installed on the VLT as part of a large ESO program of around 250 hours of observations.

“Quasars are among the brightest objects observable in the early Universe, but because of their distance, they are quite faint in terms of observed brightness,” explains co-author Valentina D’Odorico of INAF in Trieste, which is responsible for the Scuola Normale Superiore in Pisa is affiliated and principal investigator of the observational program on which the study is based. “The large amount of time spent observing these objects and X-Shooter’s unique capacities in terms of efficiency, wavelength coverage and resolving power have allowed us to obtain spectra of very good quality that have made possible this interesting result.”

“We have had evidence for a number of years that black holes, which are 1 billion times more massive than the Sun, could eject strong winds into their surroundings at speeds of 20 percent the speed of light,” adds Andrea Ferrara, a professor at Scuola Normal Superiore (SNS) and co-author of the study. “Today we have confirmation of this thanks to data obtained with a European telescope by a team with strong Italian influence and leadership. The SNS contributed to this on the theoretical interpretation side. The discovery of these spectacular galactic winds at times so distant might have had tremendous and as yet unexplored implications for the formation and evolution of galaxies like ours. We will address these questions in the ongoing continuation of this study.”

The program was not originally designed for this scientific goal, but to study mainly intergalactic gases in the early Universe. Such winds were thought to be rare, based on information from nearby quasars. “Fortunately, we said earlier, because these features complicate the reconstruction of intrinsic quasar emission, they were undesirable for astronomers in our collaboration studying the intergalactic medium along the line of sight,” says D’Odorico. “Unexpectedly, we found that these winds are very common in the young universe, which complicated our analysis but gave us the opportunity to discover a very important result.”

Simulated Webb images of the quasar and the galaxy surrounding the quasar

More information:
M. Bischetti et al, Black Hole Growth Suppressed by Strong Outflows at Redshifts 5.8–6.6, Nature (2022). DOI: 10.1038/s41586-022-04608-1

Provided by the Italian National Institute of Astrophysics

Citation: Winds in black holes aren’t what they used to be (2022, May 13), retrieved May 14, 2022 from

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