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Cette illustration offre un aperçu réaliste du noyau de Messier 77. À l’instar des autres noyaux actifs de galaxie, les régions centrales de Messier 77 sont alimentées par un trou noir entouré d’un mince disque d’accrétion, en périphérie duquel se trouve un volumineux anneau ou tore de gaz et de poussière. Dans le cas de Messier 77, cet anneau dense masque totalement la présence du trou noir supermassif. Ce noyau actif de galaxie présente vraisemblablement des jets, ainsi que des vents de poussière, qui s'échappent de la région située en périphérie du trou noir, perpendiculairement au disque d'accrétion qui l'entoure. © ESO, M. Kornmesser et L. Calçada

Black holes hid behind all kinds of active galactic nuclei

L ‘Avalanche Black hole theory confirmations with a statement fromESO Who accompanies printed in the famous newspaper temper nature Which can be freely referenced in arXiv. In 2015, we celebrated Centenary of Einstein’s final discovery of his theory of general relativity In the same year it was discovered on Earth for the first time gravitational waves Coming from another amazing prediction of his theory of relativity of gravity, black holes. In 2019, the first image of a black hole taken was revealed L ‘event horizon telescopeThe black hole at the heart of galaxy M87.

For decades, these relativistic stars were thought to be in their massive form, that is, contain at least a million masses Solar energy, sometimes several billion, is the origin of active galactic nuclei (AGN where active galactic nucleus, in English) has been particularly highlighted by radio astronomers, but also by Astronomy scientists Without AGN necessarily being sources radio. These active galactic nuclei are characterized by particularly active phenomena of one form or another, for example Jets of relativistic matter over thousands of light yearsa discovery that interests them and which is now at the fore thanks to the observations made withInterferometer the very large telescope European Southern Observatory (ESO’s VLTI).

Active galactic nuclei (AGNs) are highly energetic sources fueled by supermassive black holes. This short video provides insight into these particular objects through the recent discovery of an active galactic nucleus in the center of the Messier 77 galaxy. European Southern Observatory (ESO)

A zoo of active galactic cores

The most exciting active galactic nuclei are quasars Which at first glance seems stars seen at telescope While they are powerful radio sources, their precise determination of the distances observed in the early 1960s led to the recognition that they were objects whose size wasthe size from the solar system, yet it is able to release as many of them as possibleenergy of great stars galaxy all like Milky Way.

In the end, astronomers understood that AGNs can be described in three main categories, radio galaxies, sievert galaxies and the quasars with partitions. Some are very bright both in the visible and in the radio, and others are in only one of these spectral ranges. Some have jets of Themeothers do not.

Thus, radio galaxies are rather ordinary looking galaxies elliptical galaxies giants or lenticular galaxies, but emit strongly in the radio field. The emitted radio radiation can be hundreds of times stronger than that of so-called ordinary galaxies – we know for example the state of the so-called source chicken, which is a million times brighter than our Milky Way. An important feature of radio galaxies is their presence, and sometimes thousands of themlight years From their center, from the two lobes where mostepisode radio. This is the end of very high ejection material jets Speed The ones we mentioned earlier and in which we can see an artist’s illustration in the video above.

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sievert galaxies are spiral galaxies It was first observed in 1943 by Karl Seifert. We can mention galaxies NGC 1410 in constellation From Eridano and Messier 77 in the Baleine region. It is much brighter than an ordinary galaxy, not only in the radio, but also in the visible with its nucleus in particular emitting as much light as the rest of the stars of these galaxies.

Jean-Pierre Lumenet, director of research at CNRS and Françoise Coombes, professor at Collège de France, spoke to us about black holes and especially supermassive black holes in galaxies that lie behind AGNs. © Fondation Hugot of the College of France

We ended up developing the idea, described by the so-called Unified Model of AGN, that behind all these AGNs were hiding the same type of object, but seen from different angles and at different time intervals. The universe, and specifically, as we have said, supermassive black holes that emit a huge amount of energy after complex, and not always well understood, processes.accumulation of matter (Mainly in the form of cold bristles) and relative hydrodynamics.

Thus, in a region hardly larger than the solar system at most, there must be a torus of dust and neutral gases surrounding an accretion disk of dust, gas and finally matter ionized by the heat It is released by viscous friction in this disc and falling on a black hole care alternately.

Hot plasma enters the atmosphere of a black hole, that is, a regionspacetime Any falling object rotates radially, then participates in a complex mechanism, explained in part by Blandford and Znajik, in which the gravitational energy of falling matter and especially the rotational energy of a black hole is converted into intense radiation and jets of matter along the axis of rotation of the compressed star.

Astronomers have observed different types of AGNs. Some, called blazars, are very bright and can show differences in brightness over time scales of only hours or days, while another type, called quasars, are also very bright but tend to show lower fluctuations than blazars. Severt galaxies, which come in two forms (1 and 2), are another type of active galactic nucleus, surrounded by easily detectable host galaxies. The galaxies Seyfert 1 and Sefert 2 have a bright core. However, those of the Seyfert 2 type tend to be more conservative. The unified AGN model states that despite their differences, all AGNs have the same basic structure: a supermassive black hole surrounded by a thick ring, or hoop, of dust. According to this model, any difference in appearance between AGNs results from the angle from which we observe the black hole and its massive ring from Earth. Thus, the type of active galactic nuclei we observe depends on how dark the black hole is along its line of sight, sometimes completely obscured by the ring. © European Southern Observatory (ESO), L. Calçada and M. Kornmesser

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Unified model of active galactic nuclei

Today, it is therefore a teamastrophysicists, led by doctoral student Violetta Jamez-Rosas from Leiden University in the Netherlands, who has just provided new evidence of the importance of a unified AGN model by making the most accurate observations yet of the galactic center. 47 million light-years from the Milky Way in Piscesrevealing the presence of a thick disk of cosmic dust and gases that hides a giant black hole.

ESO press release revealing this discovery, made possible by the Matisse tool (Medium Infrared Multiple Spectrophotometer) Installed on the VLTI, he presents it as a very serious confirmation of the viability of the unified model developed thirty years ago. located in desert From Atacama in Chile, this machine collects light Infrared They were collected by the four 8.2-meter telescopes that make up very large telescope (VLT) from ESO using a technology called Interferometry The optics are long base, which actually makes it possible to have a much larger telescope, powerful Precision Superior detail control like never before.

Matisse is able to detect a wide range of wavelengths Infrared, allowing us to see dust and measure temperatures accurately. Since the VLTI consists of a very large interferometer, it provides sufficient resolution to study phenomena that occur within distant galaxies such as Messier 77. The obtained images show differences in temperature andabsorb From clouds Gas around a black hole ‘,” outlines Walter Jaffe, co-author of the study and professor at Leiden University.

The true nature of dust clouds, their role in feeding the black hole, as well as the appearance they take on as seen from Earth, have long been fundamental questions for any researcher working on active galactic nuclei. Although no single result can answer all the questions that arise, a major step has just been taken in our understanding of how AGNs work.explains Violetta Gamez Rosas who adds, Our results should provide a better understanding of the inner workings of the AGN. It could also help us better understand the history of the Milky Way, which has a supermassive black hole at its center that may have been active in the past. »

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The researchers now want to extend their observations, using ESO’s VLTI, to a larger sample of galaxies, in order to confirm the validity of the unified AGN model.

Bruno Lopez, l’un des membres de l’équipe et responsable principal de l’instrument Matisse à l’Observatoire de la Côte d’Azur, situé à Nice en France, ajoute quant à lui et toujours dans le communiqué de l’ESO that : “ Messier 77 is a true AGN prototype. His study prompts us to expand our observations program and improve Mattis in order to study a larger sample of AGNs. “.

This research program should take on a new dimension when itvery large telescope (ELT) of ESO will enter service before the end of this contract.

Very greedy supermassive black holes. All galaxies have a supermassive black hole at their center, the masses of which range from one million to a few billion solar masses. There is a proportional relationship between the mass of these black holes and the mass of galactic bulges, indicating that star formation and black hole feeding occur simultaneously. Somehow, galaxies and their black holes grow in a symbiosis. When gas falls toward the center of the galaxy, the black hole swallows as much of it as possible, but the mass it can absorb is limited. The fall of matter into the black hole releases a great deal of energy, in the form of radiation, and also in the form of kinetic energy. A galactic nucleus becomes active, either a sievert nucleus or a quasar. Winds and jets of plasma from the black hole attract the surrounding interstellar gas. Molecular gas flows around active cores have recently been revealed, carrying so much mass that they can have a major impact on the evolution of the host galaxy, regulating or even stopping the gas supply to star formation. Voracious black holes, by spitting out their own food, regulate star formation. We will explain in detail these phenomena, perhaps at the origin of the proportionality between the masses of black holes and LEDs. Françoise Combs is an astronomer at the Paris Observatory in the Laboratory for the Study of Radiation and Matter in Astrophysics (Lerma). His current field of research concerns the formation and evolution of galaxies. © Ecole Normale Supérieure – PSL

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