Astronomers from the University of Texas and the University of Arizona have discovered a fast-growing black hole in one of the most extreme galaxies known at the edge of the Universe.
The discovery of the galaxy and the black hole at its center provide new clues about the formation of the first supermassive black holes. The new work is published in the Monthly Notices of the Royal Astronomical Society.
Using observations made with the Atacama Large Millimeter Array (ALMA), a radio observatory located in Chile, the team has determined that the galaxy, named COS-87259, containing this new supermassive black hole is very extreme, forming stars at a rate of 1,000 times more than our Milky Way and containing more than a billion solar masses of interstellar dust. The galaxy shines as much from this intense burst of star formation as from the growing supermassive black hole at its center.
The black hole is considered to be a new type of primordial black hole, heavily covered in cosmic “dust”, emitting almost all of its light in the mid-infrared of the electromagnetic spectrum. Researchers have also discovered that this growing supermassive black hole (often called the active galactic nucleus) generates a powerful jet of material that travels at close to the speed of light through its host galaxy.
Today, at the center of almost every galaxy are black holes with masses millions to billions of times that of our Sun. How these supermassive black holes formed remains a mystery to scientists, especially since several of these objects have been found when the Universe was very young. Because light from these sources takes so long to reach us, we see them as they existed in the past; in this case, just 750 million years after the Big Bang, which is roughly 5% of the current age of the Universe.
What is most surprising about this new object is that it has been detected in a relatively small area of the sky (less than 10 times the size of the full Moon), suggesting that there could be thousands of similar sources in the early Universe. This is a totally unexpected finding from previous data.
The only other class of supermassive black holes we knew of in the early Universe were quasars, active black holes relatively poorly hidden by cosmic dust. These quasars are extremely rare at distances similar to that of COS-87259, with only a few dozen located across the entire sky. The surprising discovery of COS-87259 and its black hole raises several questions about the abundance of very early supermassive black holes, as well as the types of galaxies in which they typically form.
Ryan Endsley, lead author of the paper and now a postdoctoral fellow at the University of Texas said in a statement: “These results suggest that early supermassive black holes were often heavily obscured by dust, perhaps as a consequence of intense activity. of star formation in their host galaxies. This is something that others have been predicting for some years now, and it’s nice to see the first direct observational evidence supporting this scenario.”
Similar objects have been found in the more local current Universe, such as Arp 299 shown here. In this system, two galaxies collide with each other generating an intense starburst, as well as a strong dimming of the growing supermassive black hole in one of the two galaxies.
Endsley adds: “While no one expected to find this type of object in the early Universe, its discovery is a step towards a much better understanding of how billion-solar-mass black holes could have formed so early in the life of the Universe, as well as how the most massive galaxies first evolved.”