A supermassive black hole has astronomers talking

A very early supermassive black hole

Nowadays, supermassive black holes are thought to lie at the centers of nearly every galaxy, including our own Milky Way. These giant black holes have millions to billions of times the mass of our sun. But how and when did supermassive black holes first start to form, even as the earliest galaxies were forming around them? On February 23, 2023, astronomers said they’ve discovered a rapidly growing black hole in an exceedingly distant galaxy designated COS-87259. The astronomers used the words “very extreme” to describe the galaxy, and said its central supermassive black hole will help answer astronomers’ questions.

Astronomers from the University of Texas and the University of Arizona performed the new work, peering into the very early universe – that is, the very distant universe – with the Atacama Large Millimeter Array (ALMA), a radio observatory sited in Chile.

The work was published February 24 in the peer-reviewed journal Monthly Notices of the Royal Astronomical Society.

COS-87259: Why very extreme?

COS-87259, which contains the new supermassive black hole, is considered very extreme, they said, because it’s forming stars at a rate 1,000 times that of our own Milky Way. Plus, it contains over a billion times our sun’s mass worth of interstellar dust. The galaxy is distant. Astronomers are seeing it, they believe, just 750 million years after the Big Bang that brought our universe into being. So we’re seeing the galaxy as it looked when the universe was approximately 5% of the current age of the universe.

Yet astronomers can see the galaxy, and study it. Its relative brightness comes both from its rapid rate of star formation, and from the growing supermassive black hole at its center.

What about the supermassive black hole itself?

The black hole is considered a new type of primordial black hole, one heavily enshrouded by cosmic dust. As a result, it emits nearly all its light in the mid-infrared range of the electromagnetic spectrum. These astronomers’ statement said:

The researchers have also found that this growing supermassive black hole (frequently referred to as an active galactic nucleus) is generating a strong jet of material moving at near light speed through the host galaxy …

What is particularly astonishing about this new object is that it was identified over a relatively small patch of the sky typically used to detect similar objects – less than 10 times the size of the full moon – suggesting there could be thousands of similar sources in the very early universe.

This was completely unexpected from previous data.

What’s the other class of supermassive black holes?

Perhaps you know the story of Maartin Schmidt’s discovery of quasars in 1963. About all we knew about quasars at first was that they were very bright and very far away. Subsequent theories – which were borne out by observations – suggested quasars were very young galaxies in the early universe, with active black holes in their centers that are relatively unobscured by cosmic dust. The astronomers commented:

These quasars are extremely rare at distances similar to COS-87259, with only a few tens located over the full 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.

What cosmic dust might be hiding

Ryan Endsley, the lead author of the new paper, commented:

These results suggest that very early supermassive black holes were often heavily obscured by dust, perhaps as a consequence of the intense star formation activity in their host galaxies. This is something others have been predicting for a few years now, and it’s really nice to see the first direct observational evidence supporting this scenario.

The astronomers commented that similar types of objects have been found in the more local, present-day universe, such as Arp 299. In this system, two galaxies are crashing together, generating an intense starburst as well as greatly concealing the growing supermassive black hole in one of the two galaxies.

Endsley added:

While nobody expected to find this kind of object in the very early universe, its discovery takes a step towards building a much better understanding of how billion solar mass black holes were able to form so early on in the lifetime of the universe, as well how the most massive galaxies first evolved.

Bottom line: Fast star formation – and a central supermassive black hole obscured by dust – characterize the discovery of a new, exceedingly distant galaxy labeled COS-87259. It and its central supermassive black hole might provide clues to other galaxies and black holes in the very early universe.

Source: ALMA confirmation of an obscured hyperluminous radio-loud AGN at z = 6.853 associated with a dusty starburst in the 1.5 deg2 COSMOS field

Via Royal Astronomical Society