The more we study the Universe, the more likely it is that each galaxy will orbit a cosmic colossus – a supermassive black hole, feeding the galactic nucleus.
There are many things we don’t know about these huge objects – including the frightening question of how they grow so much – but new research could help us fill in some gaps. According to a new radio survey of all galaxies in a region of the sky, every supermassive black hole in a galactic nucleus devours matter, although they do it a little differently.
“We are getting more and more indications that all galaxies have enormously large black holes in their centers. Of course, they must have grown to the present mass,” said astronomer Peter Barthel of the University of Groningen in the Netherlands.
“It seems that thanks to our observations, we are now considering these growth processes and we are beginning to understand them slowly but surely.”
There is a funny gap in the range of masses of black holes, which means that we are missing an important piece of the puzzle about how supermassive black holes form and grow. Black holes in the stellar mass – those that formed from the collapsed core of a massive star – were detected only up to 142 times the mass of the Sun, and even that was heavier than usual, the product of a collision. between two smaller black holes.
Supermassive black holes, on the other hand, are usually between a few million to a billion solar masses. You would think that if supermassive black holes grew out of stellar ones with mass, there would be a lot of intermediate holes there, but very few detections were made.
One way we can try to figure it out is by studying the black holes that we have detected, to see if their behavior can give us clues; this was done by a team of astronomers led by Jack Radcliffe of the University of Pretoria in South Africa.
Their focus was a region of space known as GOODS-North, located in the constellation Ursa Major. This region, the subject of a Hubble deep sky study, has been well studied, but primarily in optical, ultraviolet, and infrared wavelengths.
A section of GOODS North, with each point a galaxy. (NASA / ESA / G. Illingworth / P. Oesch / R. Bouwens and I. Labbé and scientific team)
Radcliffe and his team performed region analyzes using a range of wavelengths up to X-rays, adding radio observations using very long basic interferometry to the mixture. Thus, they identified active galactic nuclei – those that contain an active supermassive black hole – that were bright at different wavelengths.
When supermassive black holes are actively gathering material – leaking gas and dust from the surrounding space – the material heats up, shining with electromagnetic radiation bright enough to be seen over vast cosmic distances.
Depending on how much dust hides the galactic nucleus, some wavelengths of this light may be stronger, so a single wavelength cannot be used to identify all active galactic nuclei in a patch of sky.
Equipped with this additional information, the team conducted a study of the AGN in GOODS-North and made several observations.
The first was that not all active accretions are the same. This may sound crazy and I have certainly noticed various supermassive black holes that accumulate at different speeds, but the data is still useful. The researchers found that some active supermassive black holes devour the material at a much faster rate than others, and others do not devour too much.
They then investigated the presence of starburst activity – that is, a region and a period of intense star formation – that coincides with an active galactic nucleus.
It is believed that feedback from an active galactic nucleus can extinguish star formation by blowing out all the material stars from which they are formed, but some studies have shown that the opposite can happen – that shocked and compressed feedback material can collapse into stars. babies.
They found that some galaxies have stellar explosion activity and others do not. Interestingly, the ongoing activity of stars may make an active galactic nucleus more difficult to see, suggesting that more investigation will need to be done to better define the role of feedback in extinction.
Finally, they studied relativistic jets that can shoot from the poles of a supermassive black hole during active accretion. These jets are thought to consist of a small fraction of material that becomes directed along magnetic field lines from the inner region of the storage disk to the poles of the black hole where it is thrown into space as jets of ionized plasma, at speeds a significant percentage of the speed of light.
We are not entirely sure how and why these jets are formed, and the team’s research suggests that the accumulation rate of the material does not play a huge role. They found that jets form only sometimes and that it doesn’t matter if a black hole eats quickly or slowly.
This information, the researchers said, may help to better understand the accumulation behavior and growth of supermassive black holes. And, they said, it also shows that radio astronomy may play a more significant role in these studies in the future.
Which means that in the future, we’ll have a more powerful set of tools to try to unravel one of the most puzzling mysteries of black holes – where the hell do even supermassive chonkers come from?
The team’s research was published and accepted in two papers in Astronomy and astrophysics. They can be found here and here.