Superkick: Galaxy mergers can eject the central supermasive black hole

[D H]

Imagine a spinning skater. She pulls her arms in a little and spins faster. She brings her arms all the way into her chest, and spins really fast, and then bam! she rockets up into the sky. Seven years ago, computer simulations revealed a configuration of two spinning black holes that merged in this way, jumping out of their orbital plane with a velocity of several thousand km/s. This is weird. It’s also important. We know that large galaxies host supermassive black holes at their centers. We also know that galaxies merge, presumably introducing their black holes to one another. If the newly formed black hole were to exit the galaxy entirely, it could carry its accretion disk with it, and be observable as a displaced core.​

For more (and also for references), see http://astrobites.org/2014/03/18/a-history-the-superkick-papers/.

 

[Drakkith]

Oh my... I wouldn't want to come across one of those in a dark alleyway.

 

[Greg Bernhardt]

What would happen to the shape of the galaxy if it's center black hole escaped?

 

[phinds]

Weird indeed, but interesting. I'll bet skaters wish they could do that

 

[Drakkith]

What would happen to the shape of the galaxy if it's center black hole escaped?

If we were to magically remove our own SMBH, not much, at least on the large scale. The multi-million solar mass of material is a very tiny fraction of the overall mass of our galaxy. We're talking a total estimated mass of 1,500,000,000,000 (1.5x10¹²) solar masses for the galaxy, compared to 4,500,000 (4.5x10⁶) solar masses for the SMBH.

In reality, two galaxies merging/interacting would be severely disrupted thanks to their mutual gravitational forces.

 

[Damo ET]

Wow! That is pretty cool. I wonder if this phenomena can explain some of the truly random looking galaxy types?Damo

 

[HeLiXe]

What would happen to the shape of the galaxy if it's center black hole escaped?

It would get all funky and stuff

I actually thought about this immediately. In galactic scenarios like this I always construct a mental model of the situation (no matter how incorrect). As DH presented this with angular momentum, I imagine the stars in the galaxy would also draw near the black hole before and as it ejects so the galaxy would at first look like a ball in a net (the net being the stars) with the net being affected by the other stars and massive components of the galaxy and colliding galaxy.

 

[vinven7]

Does the supermassive black holes at the center of each galaxy serve some function in the galaxy (shape stabilization etc .. I don't know) that we know of?

 

[Chronos]

SMBH's are thought to be essential in galaxy formation. Nearly all of them, so far as we can tell, have one. The role they play in that respect is poorly understood.

 

[phinds]

SMBH's are thought to be essential in galaxy formation. Nearly all of them, so far as we can tell, have one. The role they play in that respect is poorly understood.

I would also think that the role they play AFTER the formation is unclear. Their mass is a very small fraction of the total mass of the galaxy, so after the formation, are they still needed? Would it really matter if they disappeared (magically) ?