Many supermassive black holes roam between galaxies

In the early 1960s, the discovery of quasars stunned them astronomers. If one took their spectral redshifts seriously in accordance with the Hubble-Lemaître law, they had to be considered as several billion apart.light years and incredibly bright, too much for the radiation produced to be the effect of thermonuclear reactions in stars. Also, from 1964, the big astrophysicists Russian Yakov Zel’dovich and Igor Novikov (and the US Edwin Salpeter) had they proposed that the quasars, more generally active nuclei of galaxies, be supermassive black holes accreting matter. In 1971, Donald Lynden-Bell and Martin Rees proposed for their part that there was one in the heart of the Milky Way. At least since the early 1990s, it seemed clear that most large galaxies were probably to shelter in their center one of these compact stars, which the observations did not cease supporting. Today, we can even make images of it, as the members of l’Event Horizon Telescope with M87 *.

Observations also show colliding galaxies and it has become clear that in at least some cases the fusions galaxies would lead to fusions of supermassive black holes, which contributed to their growth and partly accounted for the masses reached by these objects, ranging from a few million to several tens of billions of solar masses. In fact also, we clearly see in some galaxies two or even three supermassive black holes, which is easily explained if this growth mechanism is operative. We have had reason to think despite everything for ten years, first because of simulations and finally there also of observations, that most of the growth of these objects is done by the accretion of cold currents of hydrogen and helium channeled by filaments of dark matter.

Supermassive black holes that do not “settle” in the heart of galaxies

Among the scholarly cosmological simulations on supercomputers allowing us to understand what is happening in the kingdom of galaxies and their interactions with the supermassive black holes they contain, there is one called Romulus. It takes into account a large number of celestial bodies and a series of loops of feedbacks deriving from several phenomena falling within a description nonlinear physics in play. The Romulus simulation takes into account in particular a modelization more preciseaccretion matter by a supermassive black hole as well as the famous formula known as ” dynamic friction »By the great Indian astrophysicist and Nobel Prize winner physique Chandrasekhar describing the loss ofenergy of a massive celestial body, like a star or a black hole, in movement in the gas self-gravitating stars in a galaxy.

In the context of the Romulus simulation, taking this formula into account shows in particular that supermassive black holes can take a long time to enter. coalescence after the merger of the two galaxies that contained them, or even stay in orbit around the galaxy produced.

Astrophysicist Angelo Ricarte, from Center for Astrophysics | Harvard & Smithsonian (CfA) has just published with his colleagues Michael Tremmel, Priyamvada Natarajan, Charlotte Zimmer, all of Yale University, and Thomas Quinn of the University of Washington, an interesting article in Monthly Notices of the Royal Astronomical Society and free access on arXiv, reporting new results on this subject with the Romulus simulation.

This is the continuation of work that they have been carrying out on this subject for several years and they announce that they have arrived at an astonishing prediction. About 10% of the mass contained in the form of supermassive black holes is not found in the form of these compact stars in the heart of galaxies but in the form of supermassive black holes wandering around large galaxies, in their halo of black matter, and left in this situation during minor galaxy mergers.

This portion was larger and larger as we go back in the past.

Chandra discovers wandering black hole of 100,000 solar masses

Article by Laurent Sacco published on 10/10/2016

Giant black holes are not all wisely lurking in the heart of galaxies. Some are nomads. We have just discovered the brightest of them in the field of X-rays, probably following his encounter with a star he devoured billions of years ago.

The collisions de galaxies followed by mergers are frequent in the cosmos. It is also believed that part of the growth process of galaxies is done in this way, the other part involving currents of cold gas that these objects accrete.

As massive black holes are present in almost all galaxies – in the form of black holes of intermediate masses for the smallest and in the form of supermassive black holes for the largest – black hole mergers must also occur.

We sometimes observe, in a galaxy, the presence of two giant black holes in his heart, testifying to a recent merger on the scale of the history ofuniverse. These black holes are detected in particular by emissions X-rays from a disk of hot matter that forms when they accrete matter.

A very bright X-ray source

Astrophysicists who study these phenomena therefore rely particularly on telescopes X-ray systems put into orbit (the most famous are Chandra, for the Nasa, and XMM Newton, for’THIS). An article available on arXiv also announces that a fascinating discovery was made by patiently analyzing the data collected by these instruments by observing a region of the sky of which about 500 images taken by the Hubble Space Telescope were gathered to constitute the extended Groth band, in English Extended Groth Strip1 (EGS1). It is a wide-field image of a region between the constellation Ursa Major and that of Bouvier.

In the early 2000s, Chandra and XMM Newton detected there a particularly bright but transient source of X-radiation which now appears in the archives of astrophysicists under the name XJ1417 + 52. Measurements indicate that it was 4.5 billion light years from the Milky Way, right next to a lenticular galaxy called SDSS J141711.07 + 522540.8, or more soberly GJ1417 + 52.

A black hole, a remnant of a dismantled dwarf galaxy?

XJ1417 + 52 was clearly one of the hyper bright X sources or in English hyper-luminous X-ray source (HLX). The amount of energy released in this area of wave length and its characteristics are easily explained if we are in the presence of a black hole accreting matter and whose mass must be around 100,000 solar masses, therefore a black hole of intermediate mass, since supermassive black holes contain from a few million to a few billion solar masses.

The source XJ1417 + 52 not being located in GJ1417 + 52, it is about a wandering black hole, also called nomad. This probably belonged to a galaxie woman passed too close to the lenticular galaxy and which was dismantled by the tidal forces.

We already knew of such nomadic black holes but, at the maximum of X emissions, the brightness reached by XJ1417 + 52 exceeded by a factor of 10 that of other stray black holes detected so far. Moreover, this source holds another record: it is 10 times farther away than that associated with the previous nomadic black hole which held the distance record.

It is reasonable to assume that the X-luminosity peak occurred when a star got too close to the intermediate black hole and underwent similar processing to the scenario of the stellar pancakes, proposed a few decades ago by Jean-Pierre Luminet and Brandon Carter.