The more we study the Universe, the more likely it is that each galaxy will orbit a cosmic colossus, a supermassive black hole, that feeds the galactic core.
There are many things we don’t know about these giant objects, including the amazing question of how they grow so huge, 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 so a little differently.
“We have more and more evidence that all galaxies have hugely massive black holes at their centers. Of course, these must have grown to their current mass,” said astronomer Peter Barthel of the University of Groningen in the Netherlands.
“It seems that, thanks to our observations, we now have these growth processes in sight and we are slowly beginning to understand them.”
There’s a fun gap in the massive range of black holes that means we’re missing an important piece of the puzzle of how supermassive black holes form and grow. Black holes of stellar mass – those formed from the collapsed core of a massive star – have only been detected up to 142 times the mass of the Sun, and even that was heavier. of the usual, 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. It would be thought that if supermassive black holes grew out of those of stellar mass, there would be many of intermediate mass out there, but few detections have been made.
One way to try to figure this out is by studying the black holes we have to own detected, to see if their behavior can give us clues; this is what a team of astronomers led by Jack Radcliffe of the University of Pretoria in South Africa did.
His focus was on a region of space known as GOODS-North, located in the constellation Ursa Major. This region, the subject of a Hubble deep sky survey, has been well studied, but mainly in optical, ultraviolet, and infrared wavelengths.
A PRODUCTS section to the north, with each point a galaxy. (NASA / ESA / G. Illingworth / P. Oesch / R. Bouwens and I. Labbé and the scientific team)
Radcliffe and his team performed analysis of the region using a range of wavelengths up to X-rays, adding radio observations using very long baseline interferometry to the mixture. Thus, they identified active galactic nuclei – those that contained an active supermassive black hole – that were bright at different wavelengths.
When supermassive black holes are actively accreted, dropping gas and dust from their surrounding space, the material heats up and glows with electromagnetic radiation bright enough to be seen at great cosmic distances.
Depending on the amount of dust that obscures the galactic nucleus, some wavelengths of this light may be stronger, so a single range of wavelengths cannot be used to identify all active galactic nuclei in a piece of cell.
Equipped with this additional information, the team conducted an AGN study at GOODS-North and made several observations.
The first was that not all active accretion is the same. This may seem obvious, and we have certainly observed different supermassive black holes growing at different rates, but the data are still useful. The researchers found that some active supermassive black holes devour material at a much faster rate than others, and some do not devour much.
They then investigated the presence of stellar explosion activity, i.e., a region and a period of intense star formation, which coincides with an active galactic nucleus.
It is believed that the feedback of an active galactic nucleus can attenuate star formation by blowing up all material stars, but some studies have shown that the opposite can also happen: that the material impacted and compressed by the feedback can collapse. in baby stars.
They found that some galaxies have stellar explosion activity and others do not. Interestingly, the ongoing activity of starbursts may make an active galactic nucleus more difficult to see, suggesting that more research will be needed to better define the role of feedback in extinguishing.
Finally, they studied relativistic jets that can fire from the poles of a supermassive black hole during active accretion. These jets are believed to consist of a small fraction of material that wraps along the lines of the magnetic field from the inner region of the accretion disk to the poles of the black hole, where it is thrown into space in shape. of ionized plasma jets, at speeds a significant percentage of the speed of light.
We’re not entirely sure how and why these rays form, and team research suggests that the rate of material accretion doesn’t play a huge role. They found that jets only form sometimes and that it doesn’t matter if a black hole eats quickly or slowly.
This information, according to the researchers, may help to better understand the accretion behavior and growth of supermassive black holes. And, they said, it also shows that radio astronomy may play a more important 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 baffling mysteries of the black hole: where do supermassive devils come from?
The team’s research has been published and accepted in two papers a Astronomy and astrophysics. They can be found here and here.