- 2998 - GALAXIES - when galaxies collide? What happens to the central black holes growing at the cores of each? A new study using the Chandra X-ray Observatory and several other telescopes reveals new information about how many black holes remain after these galactic smash ups.
--------------------------------- 2998 - GALAXIES - when galaxies collide?
- Astronomers want to learn more about galactic collisions because the subsequent mergers are a key way that galaxies and the giant black holes in their cores grow over cosmic time.
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- Astronomers have found seven triple galaxy mergers located between 370 million and one billion light years from Earth. What happens to their supermassive Blackholes when galaxies collide?
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- Three galaxies swirling into one another until they collide – and they all have supermassive black holes at their core!
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- The 7 colliding systems in question ranged between 370 million and one billion light years away, so any light coming from them is obviously very difficult to detect. X-rays are the wavelength most descriptive of blackhole interactions due to their ability to detect material being absorbed into the blackhole and being heated to millions of degrees in the process.
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- The Chandra X-ray observatory was used to observe these seven systems. The team was most interested in whether or not the supermassive black holes potentially at the center of these galaxies merged together.
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- A merger of supermassive black holes do in fact merge, there is the additional question of whether they emit gravitational waves, as have been first detected for stellar-sized black holes not long ago.
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- The theory surrounding the merger of these colossal objects states that if there are only two in a system, they might not be able to get close enough to each other to merge. However, adding a third black hole to the system can destabilize the system, allowing two or more to merge, in a supermassive version of the three-body problem.
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- What they found was a mix of outcomes ranging from a system with three separate blackholes still existing to a system with no x-ray emissions from blackholes at all. Other results included four systems with two growing supermassive blackholes, and one that had a single supermassive blackhole in it.
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- It’s not clear yet what these findings will mean for understanding the further growth and evolution of blackholes in such extreme environments as a trifecta or merging galaxies. But as we continue to collect and archive more data about the universe.
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- Chandra data targeting these systems to detect X-ray sources marking the location of growing supermassive blackholes. As material falls toward a blackhole, it gets heated to millions of degrees and produces X-rays.
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- Chandra, with its sharp X-ray vision, is ideal for detecting growing supermassive blackholes in mergers. The associated X-ray sources are challenging to detect because they are usually close together in images and are often faint.
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- Out of seven triple galaxy mergers there is one with a single growing supermassive blackhole, four with double growing supermassive black holes, and one that is a triple. The final triple merger they studied seems to have struck out with no X-ray emission detected from the supermassive black holes. In the systems with multiple blackholes, the separations between them range between about 10,000 and 30,000 light years.
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- Once they found evidence for bright X-ray sources as candidates for growing supermassive black holes in the Chandra data, the researchers incorporated archival data from other telescopes.
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- The Chandra and “WISE” data show that the system with growing supermassive black holes has the largest amount of dust and gas. This matches theoretical computer simulations of mergers that suggest higher levels of gas near blackholes are more likely to trigger rapid growth of the blackholes.
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- Studies of triple mergers can help scientists understand whether pairs of supermassive black holes can approach so close to each other that they make ripples in spacetime called gravitational waves. The energy lost by these waves will inevitably cause the black holes to merge.
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- The “Laser Interferometer Gravitational Wave Observatory” (LIGO) and “Virgo array” in Europe have shown astronomers that stellar-mass blackholes create gravitational waves and merge, but it is not known if supermassive blackholes do.
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- Gravitational interactions from a third supermassive blackhole may prevent this stalling process. Studies of supermassive blackholes in systems where three galaxies are merging are therefore important for understanding whether the nightmare scenario might apply.
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- Other materials about the findings are available at: http://chandra.si.edu
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January 23, 2021 GALAXIES - when galaxies collide? 2998
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