by Astronomers have seen a supermassive black hole throwing mad streaks on a galactic scale as it feeds, figuratively “flooding the table” and cutting off its parent galaxy’s supply of gas needed to birth stars.
The onboard transport comes in the form of ultrafast wind rising from the supermassive, light-snacking black hole, which sits in a separate galaxy on average. The galaxy is called Markarian 817 (Mrk 817) and is located 430 million light years away in the constellation Draco; the event was detected by the European Space Agency’s (ESA) XMM-Newton space telescope.
Supermassive black holes with masses millions, or even billions, of times that of the sun are thought to reside at the heart of all galaxies. In some cases, however, these cosmic titans are surrounded by disks of gas and dust called “accretionary disks” that “feed” them.
When this happens, the massive gravity of these black holes overwhelms the gaseous and dusty material, causing it to burn. In addition, powerful magnetic fields funnel material that does not fall to the black hole to its eventual poles, where the material is blasted away at near-light speeds. As a result of this turbulent activity, these regions, called “active galactic nuclei,” or AGNs, can often overwhelm the combined light of all the stars in the galaxies around them.
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In some cases, AGN-powered supermassive black holes exhibit even more drastic behavior, spilling over their entire cosmic dinner table by swallowing gas in the surrounding accretion disks out in all directions. This results in “ultra-fast black hole winds.”
When this happens, the black hole is not only stripped of gas to fuel it, but it also expels gas from its host galaxy, halting star birth over a vast region.
Previously, astronomers had only seen these ultra-fast black hole winds coming from extremely bright AGNs ferociously feeding black holes.
“This is the first time we have seen very fast winds ejected from the active disk of a galactic nucleus (AGN) around a supermassive black hole that is accreting at a rate much lower than the rate at which we expect such winds to act ,” Elias Kammoun, staff member and postdoctoral fellow at Sapienza University in Rome, told Space.com.
Before this discovery, Kammoun said, it was commonly assumed that very rapid wind generation only occurred in cases where gas was shown spiraling down the supermassive black hole at a very high rate.
“In this regime, a large amount of energy is released and radiated away, which is a key factor in driving disc winds,” he continued. “Several pieces of evidence have shown that the activity of central black holes plays a central role in reshaping the host galaxy and affecting its evolution, which we call AGN feedback. However, the conditions under which this feedback can be triggered are not still very clear.
“Finding ultrafast winds in a moderate accretion source will make us rethink the way we see winds in AGNs.”
Black hole fell silent before moving the table
Mrk 817 signaled to astronomers that something dramatic was afoot when the AGN went eerily quiet. Normally, you would expect it to be bursting with high-energy light, such as X-rays.
Miranda Zak, a graduate student at the University of Michigan and team leader, first spotted the strange interference on NASA’s Swift observatory, later following up with the more sensitive XMM-Newton. Ultimately, Zak discovered that ultra-fast winds emerging from the accretion disk at the core of Mr. 817 were absorbing X-rays, effectively masking any signals coming from the central supermassive black hole.
Then, further analysis of the X-rays from this AGN showed that the central region of Mrk 817 was not just sending out a single puff of gas, but was blowing a large gale across the accretion disk. And, according to their comments, they can still be seen doing so. These winds can last for hundreds of days and consist of at least three distinct components, each moving at a fraction of the speed of light.
“Disc winds were not expected at all to be identified in supermassive black holes that accreted at normal rates like Mrk 817,” Kammoun said. “The high accretion rate phase is supposed to be a short phase in the life of a supermassive black hole. On the contrary, the accretion phase of Mrk 817 can last much longer thanks to its moderate rate.”
He added that this has two major implications for our understanding of feeding supermassive black holes, as well as the AGNs that power them.
First, this suggests that even lightly fed supermassive black holes can eject winds powerful enough to reshape their host galaxies; they also seem to have long enough lifespans to allow for such actions.
Second, if very fast winds can arise from regions around moderately accreting black holes, such winds are likely to be more common than astronomers currently think. Therefore, scientists believe that these winds probably shaped many different galaxies, including some that we already know about.
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The discovery of winds from a long-lived quiescent black hole may someday help answer an intriguing question: Why do some galaxies like the Milky Way appear to have large, large regions at their cores? Milky way with silent black holes feeding light? form in very low numbers only?
“There is still a lot to learn about Mrk 817 in particular and the wider AGN,” Kammoun said. “This discovery changes the way we look at AGNs. It will be crucial to know how many of the moderate accreting sources actually send winds. This will help us better understand how common they can be. be.
“I believe this is only the tip of the iceberg!”
The team’s research was published Thursday (February 1) in the Astrophysical Journal.
