Black hole winds are no longer as they used to be

Artist’s impression of the environment of a supermassive black hole at the center of an active galaxy. Credit: ESO/M. kornmesser

During the first billion years of the universe, the winds blown by supermassive black holes in the centers of galaxies were much more frequent and powerful than the winds observed in today’s galaxies some 13 billion years later. Such winds were so powerful that they stunted the growth of the supermassive black holes from which they sprang. These are the results of a study led by three researchers from the Italian National Institute of Astrophysics (INAF) in Trieste, published today in the journal Nature

The work is based on observations of 30 quasars observed with the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile. Quasars are extremely bright, point-like sources in the cores of distant galaxies, emitted by the intense activity of the central supermassive black holes sucking up 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 measured the fraction of quasars in the young universe that exhibit black hole winds,” said Manuela Bischetti, an INAF researcher in Trieste and lead author of the new study. “Contrary to what we observe in the universe closer to us, we found that winds from black holes in the young universe are very frequent, 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 study exhibit black hole winds, which are much more frequent and 20 times more powerful than the winds 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 are growing much faster than their host galaxies, while in the local universe we know that black holes and galaxies evolve together,” added co-author Chiara Feruglio, INAF researcher in Trieste. . “This implies that there must have been a mechanism somewhere in the universe that slowed the growth of the black hole. Our observations have allowed us to identify this mechanism in the black hole winds that formed when the universe was 0, 5 to 1 billion years old.”

Thus, the wind-injected energy would have been able to halt further matter accretion on the black hole, slow its growth and initiate a “common evolution” phase between the black hole and its host galaxy. “This study allowed us to identify the epoch in the history of the universe when the impact of black hole winds started to become significant,” Bischetti added. “This has a huge impact on our understanding of the early stages of the 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 with approximately 250 hours of observations.

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

“We’ve had evidence for a few years now that black holes, which are 1 billion times more massive than the Sun… could launch powerful winds that flow into their environment at a speed equal to 20 percent of the speed of light,” added Andrea Ferrara. . , professor at the Scuola Normale 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 a strong Italian impression and leadership. The SNS has contributed to the theoretical side of interpretation. The discovery of these spectacular galactic winds in such distant times had enormous and untapped implications for the birth and evolution of galaxies like ours. We will address these questions in the continuation of this study.”

The program was not originally designed for this scientific purpose, but to study primarily intergalactic gas in the early universe. Based on information from more nearby quasars, such winds were thought to be rare. “Fortunately, we always said that because these features complicate the reconstruction of the 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 quasar and galaxy surrounding quasar

More information:
M. Bischetti et al, Suppression of black hole growth by strong outflow at redshifts 5.8–6.6, Nature (2022). DOI: 10.1038/s41586-022-04608-1

Provided by the Italian National Institute of Astrophysics

Quote: Black hole winds are no longer as they were (2022, May 13) Retrieved May 14, 2022 from

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