Black holes always continue to look like something to us unknown and fascinating. It is a finite region of space in whose interior it has a mass concentration high enough to generate a gravitational field such that no particle –not even light– can escape from it.
Now 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 in the early Universe. Published in Monthly Notices of the Royal Astronomical Societythe discovery of the galaxy and the black hole at its center provide new clues about the formation of the first supermassive black holes.
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 1,000 times larger 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 stream of material It travels at close to the speed of light through its host galaxy.
Today, at the center of almost all galaxies 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.
The most surprising thing about this new object, according to the authors, is that it has been detected in a relatively small area of 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.
quasars
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 similar distances to 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 at Austin, says in a statement: “These results suggest that the first supermassive black holes were often very obscured by dust, perhaps as a consequence of the intense star formation activity in its host galaxies. This is something that others have been predicting for a few years now, and it’s really 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 colliding 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.”