A rapidly growing black hole

Astronomers have discovered a rapidly growing black hole in one of the most well-known galaxies in the primordial universe
This Arp 299 system consists of a pair of galaxies, IC 694 and NGC 3690, which underwent a close encounter about 700 million years ago. As a result of this interaction, the system underwent a fierce burst of star formation. In the past fifteen years or so, six supernovae have exploded in the outermost regions of the galaxy, making this system a prominent supernova factory. Credit: NASA

Astronomers from the University of Texas and the University of Arizona have discovered a rapidly growing black hole in one of the most well-known galaxies in the primordial universe. The discovery of the galaxy and the black hole at its center provides new clues about the formation of the very first supermassive black holes. New work is published (ref.) in the Monthly Notices of the Royal Astronomical Society.

Using the Atacama Large Millimeter Array (ALMA), a radio observatory located in Chile, the team determined that the COS-87259 galaxy is extremely unusual. It forms stars at a rate 1000 times faster than the Milky Way and contains over a billion solar masses of interstellar dust. The galaxy shines brightly due to both this intense star formation and the rapidly growing black hole at its center.

A new type of black hole

This black hole is considered a new type of primordial black hole. Heavily shrouded by cosmic dust, it emits almost all of its light in the mid-infrared range of the electromagnetic spectrum. Researchers have also discovered that this rapidly growing supermassive black hole is generating a strong jet of material moving at near-light speed.

The way in which these supermassive black holes formed remains a mystery to scientists. Particularly because many of these objects were found when the universe was very young. Since the light from these sources takes so long to reach us, we see them as they existed in the past. In this specific case, we observed how it appeared just 750 million years after the Big Bang, or about 5% of the current age of the universe.

What is particularly surprising about this new object is that it was identified in a relatively small area of the sky. This suggests that there could be thousands of similar sources in the primordial universe. This is a completely unexpected result when looking at data prior to the study.

Confirmation of a decade-old hypothesis

The only other class of supermassive black holes we knew about in the primordial universe are quasars, black holes that are relatively unobscured by cosmic dust. These quasars are extremely rare, with only a few dozen located throughout the sky. The surprising discovery of COS-87259 and its black hole raises several questions about the abundance of the very first supermassive black holes.

Ryan Endsley, the lead author of the article, states, “These results suggest that the very first supermassive black holes were often heavily obscured by dust, likely as a result of the intense star-forming activity of the galaxies that hosted them. This hypothesis, predicted for decades, now has the first direct observational evidence supporting this scenario”.

Similar objects have been found in the local cosmos, such as Arp 299 shown in the photo. In this system, two galaxies are colliding, which generates intense starburst activity and heavy obscuration of the rapidly growing supermassive black hole in one of the two galaxies. “Although no one expected to find this type of object in the primordial universe, its discovery allows us to take a step towards understanding the cosmos. Now we know how billions of solar masses of black holes were able to form so early in the life of the universe” Endsley concluded.

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