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A research team led by the National Institute of Astrophysics (INAF) has once again harnessed very distant and energetic relativistic winds generated by a distant but definitely active quasar (one of the brightest discovered so far). A study published in The Astrophysical Journal reports the first observation at different wavelengths of the interaction between a black hole and its host galaxy quasar during the early stages of the Universe, some 13 billion years ago. In addition to the evidence of a gas storm generated by the black hole, the experts discovered for the first time a halo of gas extending far beyond the galaxy, suggesting the presence of material ejected from the galaxy itself through winds generated by the black hole.

The galaxy J0923+0402 is featured in the study, a galaxy far from earth with a quasar at its centre. To be precise, it has a redshift of z = 6.632, meaning the radiation we can observe on earth was emitted when the Universe was less than a billion years old. Quasar light (or quasi-stellar radio source) is produced when the galactic material surrounding the supermassive black hole gathers in an accretion disk. As the matter approaches the black hole and is then swallowed up by it, it heats up, emitting large amounts of bright radiation in both visible and ultraviolet light.

“The combined use of multi-band observations has allowed us to study the most distant quasar with a measurement of nuclear wind and the most extensive gas halo detected in remote epochs (about 50 thousand light years). This was done over a very wide range of spatial scales and from the most nuclear regions down to the circumgalactic medium,” explains Manuela Bischetti, first author of the study and researcher at INAF and the University of Trieste. 

The data described in the article is the result of the collaboration of research groups studying different frequencies of the electromagnetic spectrum. First and foremost, the X-Shooter spectrograph, installed on the ESO's Very Large Telescope (VLT), has captured bursts of matter known as BAL winds (broad absorption lines winds) capable of reaching relativistic speeds of up to tens of thousands of kilometres per second, measuring and calculating their characteristics. The powerful Chilean antennas of ALMA (ESO's Atacama Large Millimeter/submillimetre Array) were activated to search for the counterpart in the cold gas of the BAL winds and to see if it extended beyond the scale of the galaxy, receiving frequencies from 242 to 257 GHz from the dawn of the Cosmos. 

The researcher points out: 'BALs are winds that are observed in the ultraviolet spectrum of the quasar, which, given their long distance from earth, we observe at optical and near-infrared wavelengths. We used the Very Large Telescope's X-Shooter spectrograph to make these observations. We had already discovered the BAL of this quasar two years ago, but the problem was that we could not quantify how energetic it was. This BAL wind is a hot gas wind (tens of thousands of degrees) moving at tens of thousands of km/s. At the same time, ALMA's millimetre-band observations allowed us to understand what is happening in and around the galaxy by observing what happens to the cold gas (a few hundred degrees). We found that the wind also extends to the scale of the galaxy, but expectedly has lower velocities of 500 km/s, since the wind decelerates as it expands. This helped us to theorise that this mega halo of gas was created by the material that the winds ejected from the galaxy'.

The position of the energy source was then 'immortalised' first by the Hyper Suprime-Cam (HSC), a giant camera installed on the Subaru telescope and developed by the National Astronomical Observatory of Japan (NAOJ), and, more accurately, by the NIRCam, an infrared camera installed on the James Webb Space Telescope (JWST of NASA, ESA and CSA space agencies). “This quasar will be observed again by the JWST in the future to better study both the wind and the halo,” Bischetti announced.

The researcher goes on to explain the reason for this survey: 'We wondered whether black hole activity could have an impact on the early stages of galaxy evolution, and through which mechanisms this might occur. The combination of multiband data ranging from optical and near-infrared to millimetre-band observations was highly successful, the former having been used to measure the properties of the black hole and what happens in the core of the galaxy and the latter to study what happens in and around the galaxy.” The measurements carried out “are routine in the local Universe, but these results have never been obtained before at redshift z>6,” he adds.

“Our study helps us understand how gas is ejected or captured by galaxies in the Young Universe and how black holes grow and can impact galaxy evolution. We know that the fate of galaxies such as the Milky Way is closely linked to that of black holes, as these can generate galactic storms that can extinguish the formation of new stars. Studying primordial epochs allows us to understand the initial conditions of the Universe we see today,' Bischetti concludes. 

The article ‘Multi-phase black-hole feedback and a bright [CII] halo in a Lo-BAL quasar at z∼6.6’, by Manuela Bischetti, Hyunseop Choi, Fabrizio Fiore, Chiara Feruglio, Stefano Carniani, Valentina D'Odorico, Eduardo Bañados, Huanqing Chen, Roberto Decarli, Simona Gallerani, Julie Hlavacek-Larrondo, Samuel Lai, Karen M. Leighly, Chiara Mazzucchelli, Laurence Perreault-Levasseur, Roberta Tripodi, Fabian Walter, Feige Wang, Jinyi Yang, Maria Vittoria Zanchettin, Yongda Zhu, was published in The Astrophysical Journal.