Black hole winds are no longer what they used to be

Black hole winds are no longer longer than usual

An artistic impression of the vicinity of a supermassive black hole at the center of an active galaxy. Credit: ESO / M. Kornmeiser

During the first billion years of the universe’s life, winds from supermassive black holes at the centers of galaxies were much more frequent and stronger than those observed in today’s galaxies, about 13 billion years later. Such winds were so intense that they slowed the growth of the supermassive black holes that arose from them. 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. temper 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 nuclei of distant galaxies, the emission of which arises from the intense activity of central supermassive black holes that absorb surrounding matter. The host galaxies of these quasars were observed around the cosmic dawn, when the universe was between 500 million and 1 billion years old.

“For the first time, we have measured the fraction of quasars in the young universe that exhibits black hole winds,” says Manuela Peschetti, an INAF researcher in Trieste and first author of the new study. “Contrary to what we observe in the universe closest to us, we have discovered that black hole winds in the young universe are very frequent, have speeds as high as 17 percent the speed of light, and pump large amounts of energy into the host galaxy.”

About half of the quasars observed in this paper show black hole winds, which are 20 times more frequent and stronger than those found in nearby quasars 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 evolve together,” adds Chiara Viroglio, a researcher involved in the study in Trieste. “This means that at some point in the universe some mechanism must have acted, slowing the growth of the black hole. Our observations enabled us to identify this mechanism in the black hole winds that resulted when the universe was 0.5 to 1 billion years old.”

Thus, the energy achieved by the wind will be able to stop further accumulation of matter on 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 era in the history of the universe during which the influence of black hole winds began to be significant,” adds Bischetti. “This has a significant impact on our knowledge of the initial growth stages of black holes and their host galaxies, placing strong limitations on models describing the formation of the first galaxies.”

A completely unexpected discovery, made possible by high quality data from the Xshooter tool installed on VLT in the context of a large ESO program with about 250 hours of observations.

“Quasars are among the brightest objects observable in the early universe, but due to their distance, they are very faint of the observed size,” explains co-author Valentina Dodurico of INAF in Trieste, affiliated with the Scuola Normale Superiore in Pisa. and the principal investigator for the monitoring program on which the study is based. “The significant investment of time devoted to observing these objects and the unique capabilities of the X-shooter in terms of efficiency, wavelength coverage and power of analysis allowed us to obtain very good spectra which enabled this intriguing result.”

Andrea Ferrara adds: “We had indications a few years ago that black holes are a billion times the mass of the Sun… they can release strong winds that travel at 20 percent the speed of light in their surroundings.” , professor at the Scuola Normale Superiore (SNS) and co-author of the study. “Today, we have confirmation of this thanks to the data obtained with a European telescope by a team with a strong Italian footprint and leadership. The SNS has contributed to the aspect of theoretical interpretation. The discovery of these wonderful galactic winds in such distant times may have had enormous and unimaginable implications. An explorer to date on 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 goal, but to study primarily intergalactic gas in the early universe. On the basis of information from more nearby quasars, such winds were thought to be rare. “Fortunately, we used to say, as these features complicate the reconstruction of intrinsic quasar emission, they were undesirable by 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 complicates our analysis but gives us the opportunity to discover a very important finding.”

Web simulations of the quasar and the galaxy surrounding the quasar

more information:
M. Bischetti et al., Suppression of black hole growth by strong outflows at redshifts 5.8-6.6, temper nature (2022). DOI: 10.1038 / s41586-022-04608-1

Submitted by the Italian National Institute of Astrophysics

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