I Are there galaxies with 2 cores?

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The discussion centers on the phenomenon of galaxies merging, particularly focusing on the potential for galaxies to have two separate cores due to recent mergers. It is noted that while some galaxies, like M31, exhibit characteristics of a double nucleus, simulations suggest they likely contain a single supermassive black hole (SMBH). The conversation highlights the challenges astrophysicists face in understanding the mechanics of SMBH mergers, especially regarding how they approach each other without losing material. Observations of galaxies like the Antenna galaxies and the Mice galaxies are mentioned, but the consensus is that true dual-core systems are rare and may not last long before merging into a single core. Overall, the complexities of gravitational interactions and the dynamics of galactic cores are emphasized as key factors in this ongoing study.
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When discussing about galactic 'collisions' and mergers, such as the predicted future encounter between the Milky Way and Andromeda, it is often said that actual collisions among stars are extremely unlikely, it's just that the mutual gravitational influence of both galaxies on each other will gradually deform, distort, stretch or squeeze the galaxies' shapes, they will gradually engage in a gravitational dance around common centers of gravity, and slowly, if the gravitational attraction is strong enough to maintain the bond, the two structures will eventually evolve into some new shape as a new single and larger galaxy.

Assuming that the galactic cores (say both include a super-massive black hole) are following paths far from heading to each other head-on, they will also enter a gravitational dance around a common center of gravity. And all the stars from both galaxies would get involved into a highly complex motion affected by the common center of gravity of both galactic centers, and possibly by each of them individually if they pass close enough to any of them. This could in principle last for billions of years before the two cores get closer and closer to each other and finally merge into a new single galactic core, combining the mass of the two previous cores.

My question is, have we observed any such galaxies which display 2 separate cores resulting from a relatively recent merger? and if so, how do they look like? how they behave? what are their most interesting features?
And in case we have not detected any such dual-core galaxies, what would explain that fact? Wouldn't it be natural to expect that such galaxies must be out there in the right environments?

TX!
 
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Gerinski said:
My question is, have we observed any such galaxies which display 2 separate cores resulting from a relatively recent merger?

I do not believe we have. M31 has a double nucleus, but simulations show it's much more likely to have only a single SMBH at point "P2". The reason is that the lifetime of such a two core system is exceedingly short before they merge.
 
Vanadium 50 said:
The reason is that the lifetime of such a two core system is exceedingly short before they merge.
Isn't that based purely on observation?

As far as I understand, astrophysicists are stuck on the maths of what actually makes them merge. I was under the impression that SMBHs fall into each other by eating material by ejecting it, both alter it's momentum allowing them to fall into lower orbits. The linked article indicates that when they get within a few light years of each other, all of that material is gone though, no one is sure how they get any closer other than by gravitational waves, which are negligible at those distances.
 
Gerinski said:
...
My question is, have we observed any such galaxies which display 2 separate cores resulting from a relatively recent merger? and if so, how do they look like? how they behave? what are their most interesting features?...

Antenna galaxies ngc4038 and ngc 4039

220px-Antennae_Galaxies_NGC4038_NGC4039_Goran_Nilsson_%26_The_Liverpool_Telescop.jpg

The mice galaxies are not yet merged
300px-Merging_galaxies_NGC_4676_%28captured_by_the_Hubble_Space_Telescope%29.jpg


newjerseyrunner said:
...within a few light years of each other, all of that material is gone though, ...

My impression was that the space with few stars was the core. That would be 2 black holes inside of 1 merged core.
 

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newjerseyrunner said:
t when they get within a few light years of each other, all of that material is gone though, no one is sure how they get any closer

I think its closer than that. In cores the distances between stars are measured in light-minutes or hours, not years. You can get quite close before you run out of stars to eject. But even if it were light years, on galactic scales, I would say two SMBH's within even a few light years of each other in the center of the core means you have one core, not two. Where you draw the "edge" of the core is not well defined, but for any reasonable definition, the core is dominated by stars and not their SMBH's.
 
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Thanks for all the answers
 
Glad to know about this. Thank you so much for sharing.
 
Vanadium 50 said:
I think its closer than that. In cores the distances between stars are measured in light-minutes or hours, not years. You can get quite close before you run out of stars to eject. But even if it were light years, on galactic scales, I would say two SMBH's within even a few light years of each other in the center of the core means you have one core, not two. Where you draw the "edge" of the core is not well defined, but for any reasonable definition, the core is dominated by stars and not their SMBH's.
It is called final parsec problem - a few light years are right.
 
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wow nice! Thanks for placing the link here.
 

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