A primordial supermassive black hole has a mass that is difficult to explain

Artist's concept of Pōniuāʻena (Image courtesy International Gemini Observatory/NOIRLab/NSF/AURA/P. Marenfeld)
Artist’s concept of Pōniuāʻena (Image courtesy International Gemini Observatory/NOIRLab/NSF/AURA/P. Marenfeld)

An article accepted for publication in “The Astrophysical Journal Letters” reports the discovery of a very bright primordial quasar that was cataloged as J100758.264+211529.207, or simply J1007+2115, and named Pōniuāʻena. A team of researchers used three Mount Maunakea Observatories in Hawaii to identify one of the oldest known quasars, surpassed in age only by the one cataloged as J1342+0928, whose discovery was announced in December 2017.

From Earth we see Pōniuāʻena as it was about 13 billion years ago, a quasar powered by a supermassive black hole with an estimated mass of 1.5 billion times that of the Sun, almost twice the one that powers J1342+0928. This raises more than ever the problem of the quick growth of some primordial supermassive black holes.

Quasars are the brightest objects in the universe thanks to supermassive black holes that are surrounded by large amounts of materials that are heated by the enormous force of gravity to the point of generating electromagnetic emissions so intense that they’re visible billions of light years away. Despite this, it took the combined efforts of the W. M. Keck Observatory, the Gemini Observatory, and the United Kingdom Infrared Telescope (UKIRT) to locate Pōniuāʻena, a Hawaiian name.

The study of primordial objects such as Pōniuāʻena is important to understand how supermassive black holes of this kind can form so quickly, but it’s also linked to other cosmological studies. Jinyi Yang, postdoc researcher associated with the Steward Observatory of the University of Arizona and lead author of the study, explained that it’s the most distant known object with a black hole that has a mass greater than one billion solar masses. The problem is that according to theoretical models it should have started as a “seed” that had a mass of about 10,000 solar masses about a hundred million years after the Big Bang. This would be inconsistent with other models, the ones describe the initial phase of the universe’s development.

According to current models, stars and galaxies began to form around 400 million years after the Big Bang. It was the so-called epoch of reionization, a crucial period in the history of the universe in which hydrogen, which in the first period of universe life was neutral, got separated into protons and electrons. The first black holes should have started to grow during that period, but it’s difficult to reconcile the timelines of Pōniuāʻena’s growth with those of stars and galaxies’ formation.

The study of primordial quasars helps to accumulate data on the epoch of reionization because its electromagnetic emissions are altered by the intergalactic gas it passes through. Analyzing the spectrum of those emissions helps to understand the characteristics of the gas they passed through. In the case of ancient quasars like Pōniuāʻena, the hope is that they will provide data explaining its growth. The powerful and sophisticated instruments available today are very useful in these studies, even more so when a research uses various ones with different characteristics that offer a more complete picture of certain cosmic processes.

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