A possible explanation for the growth of supermassive black holes

Chandra Deep Field-South and illustration of a supermassive black hole (Image X-ray: NASA/CXC/Univ. of Rome/E.Pezzulli et al. Illustration: NASA/CXC/M.Weiss)
Chandra Deep Field-South and illustration of a supermassive black hole (Image X-ray: NASA/CXC/Univ. of Rome/E.Pezzulli et al. Illustration: NASA/CXC/M.Weiss)

An article published in the journal “Monthly Notices of the Royal Astronomical Society” describes a research about the growth mechanisms of supermassive black holes. A team of six Italian researchers led by Edward Pezzulli, a PhD student of the National Institute for Astrophysics (INAF) in Rome proposed a model that predicts that these objects can reach masses even billions of times the Sun’s not with a steady growth but with periodic “meals” that are very quick during whith they swallow huge amounts of materials.

The mystery around supermassive black holes is due to the fact that they were observed even at 12.8 billion light-years of distance, which means they existed when the universe had “only” a billion years old. It would seem a time too short for a black hole to manage to form and accumulate a mass billions of times the Sun’s.

Various researches attempted to solve what appears to be a contradiction between observations and theoretical models. Now the team that includes Edwige Pezzulli, Rosa Valiante, Maria C. Orofino, Raffaella Schneider, Simona Gallerani and Tullia Sbarrato offered a possible solution.

The researchers used data collected using NASA’s Chandra X-ray Observatory and in particular the Chandra Deep Field-South (CDF-S), a nearly 2,000-hour exposure that is the deepest X-ray image ever captured. Other data were collected by the Sloan Digital Sky Survey (SDSS).

All of these data allowed to find some black hole candidates during their growth thanks to the X-rays released when gas and dust that orbit them fall into them heating up considerably and emitting those electromagnetic radiations.

According to the model proposed by the researchers, black holes can grow very quickly by swallowing huge amounts of matter in a few growing steps. In those occasions, they become bright sources at X-rays and can therefore be observed even at huge distances. Their initial mass is in the order of one hundred solar masses and may have formed from the first generation of massive stars in the universe some hundreds of millions of years after the Big Bang.

The observations made are an initial phase of the research that gave promising results. However, in order to prove that the theory proposed by the researchers is correct, it will be necessary to observe larger portions of the sky at X-rays. It’s the only way to find enough progenitor candidates to see if this new model matches the observations.

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