Hubble finally reveals a missing link in the growth of supermassive black holes

There is no longer any doubt today that at the heart of the great galaxies there is a compact object containing from one million to several billion masses solar. Everything indicates that they are rotating Kerr black holes, even if we can still doubt it a little out of caution. We also note that there is a relation of proportionality between the mass of these supermassive black holes and the mass of the galaxy which hosts it so that the two stars must evolve together and that we cannot therefore understand the evolution of one without the other.

It is unclear how the germs supermassive black holes, however we think we understand certain aspects of their growth and, according to the now dominant paradigm which also explains that of galaxies, it is essentially by accretinghydrogen and of thehelium of big Bang channeled by filaments of cold dark matter.

We have sought to model this growth of supermassive black holes using numerical simulations properly fed with observations and leading to testable predictions. Among those who emerging the implementation of algorithms on the computers of the noosphere, there are those indicating that at the beginning of their history — when the galaxies are the place of outbreaks ofstars important less than a billion years after the Big Bang in particular and that large quantities of dust are already produced by these stars — the supermassive black holes must have been strongly surrounded by dust largely blocking the emissions of radiation resulting from the heating of the gas falling towards these compact stars.

It is only a little later that part of this cocoon will largely disappear, leaving the structure with a torus of dust surrounding a accretion disk which, when sufficiently supplied with matter produces a quasar whose radiation is no longer largely obscured by the dust cocoon.

Hubble and the light strata of the history of galaxies and supermassive black holes

There must therefore have been a transitional link between galaxies observed a few hundred million years after the Big Bang and behaving like particular starburst galaxies, galaxy starburst, as we say in English, and quasars more classic that we observe a little later in the history of the observable cosmos.

All of these steps produce emission spectra very specific according to the simulations, spectra that we can therefore try to detect associated with very old galaxies.

Again, it seems that the Hubble telescope has trumped the James-Webb telescope by allowing one of these links to be discovered for the first time. It is called GNz7q and the astrophysicists discovered its existence by continuing to analyze data collected by Hubble some time ago as part of the Great Observatories Origins Deep Survey (Goods, either in French, In-depth survey of origins by the Great Observatories).

This is an astronomical survey that combines observations from three “great observatories” of the Nasanamely the Hubble Space Telescopethe telescope spatial Spitzer and the X space telescope Chandra essentially. Goods’ objective was already a decade ago to make it possible to study the formation and evolution of galaxies in theUniverse distant, that is to say primordial.

In the present case, the observations used come from the deep field of Hubble in thenorthern hemispherea portion of the celestial vault allowing a kind of coring deep in the strata of light from the Universe, strata in the visible and theinfrared. The result of the studies which made it possible to discover the galaxy GNz7q was published in an article by Nature free access on arXiv.

In fact, Hubble does not only see in the visible and the infrared because it also makes it possible to see partly in the ultraviolet and it is in this band of wavelengths that this galaxy GNz7q was also revealed as it was only 750 million years after the Big Bang, which occurred, let us recall, approximately 13.8 billion years ago.

The data collected allows Seiji Fujimoto, astronomer at the Institute Niels Bohr from the University of Copenhagen, Denmark, and lead author of the paper Natureto affirm in a press release from NASA: Our analysis suggests that GNz7q is the first example of a rapidly growing black hole in the dusty core of a starburst galaxy at a time close to that of the first known supermassive black hole in the Universe. The properties of the object that show through the electromagnetic spectrum are in excellent agreement with the predictions of the theoretical simulations “. About the equivalent of 1,600 solar masses were then converted each year into stars of all sizes, which therefore made GNz7q very bright in ultraviolet, whereas a weak radiation in X ray is observed; this gives credence to the idea that the supermassive black hole at the heart of the galaxy is deeply hidden by a cocoon of dust.

The fact that we can finally see the missing link what is GNz7q between early starburst galaxies and galaxies with quasars in the small region of the celestial vault which is the Hubble Goods Northfield, as it is called in English, is proof that many more such objects are waiting to be discovered. In this regard, the commissioning of the James-Webb telescope should be decisive in studying a large population of these objects. Ultimately, we will therefore be able to better understand how our Milky Way and its own supermassive black hole.