What is responsible for the spinning of a galaxy?

[MikeeMiracle]

TL;DR Summary

What is responsible for the spinning of a galaxy?

If you fill a sink with water and then let it drain, the water swirls due to the rotation of the Earth influencing it. During star formation, the primordial accredisk disk spins due to it's galaxy's rotation as I understand it.

This being the case, what force made / makes the galaxy spin to begin with?

Likewise, if say a small galaxy passes through a circular galaxy, what makes the captured stars start following in the same direction as the existing stars in the galaxy?

I am assuming that the stars orbit in a plane similar to the "equator" of the black hold in the center in the same way the planets orbit the stars?

 

[Orodruin]

If you fill a sink with water and then let it drain, the water swirls due to the rotation of the Earth influencing it.

This is not entirely accurate. There is a Coriolis effect that can be observed on meter scale bodies, but in the typical situation, the Coriolis effect is not the main reason for a swirl to form in a particular direction. Unless you let the water settle for a long time, it is typically much more important how the water is poured into the drain, i.e., a pre-existing angular momentum leading to clear swirl once the water comes closer to the drain.

This being the case, what force made / makes the galaxy spin to begin with?

Same as the water drain. Galaxies will typically not form with zero angular momentum. As the gas cloud forming the galaxies contracts, conservation of angular momentum means that there will be a clear rotation with faster speeds (compare to a skater increasing rotational speed when pulling in the arms).

 

[.Scott]

If you fill a sink with water and then let it drain, the water swirls due to the rotation of the Earth influencing it.

No. There will be some motion in the water before it goes down the drain. Water with no circulation will tend to drop into the drain readily. Water that is turning in the sink will tend to stay towards the sides and will stay in the sink until it either "overflows" into the drain or looses some of its speed (through friction).

Similarly, as parts of the galaxy are pulled together by gravity, they start with motion relative to each other - giving the galaxy as a whole angular momentum.

 

[MikeeMiracle]

Ok, I think i get it.

So let's say we have a wondering black hole in intergalactic space and 2 wondering stars. Both stars are attracted by the black hole, one coming in from the "east" and one from the"west." The one with the most angular momentum will determine the direction of the eventual combined system and both stars will spin in that direction eventually once they have settle down into regular orbits?

Does that sound correct?

 

[DaveC426913]

Ok, I think i get it.

So let's say we have a wondering black hole in intergalactic space and 2 wondering stars. Both stars are attracted by the black hole, one coming in from the "east" and one from the"west." The one with the most angular momentum will determine the direction of the eventual combined system and both stars will spin in that direction eventually once they have settle down into regular orbits?

Does that sound correct?

It's correct in spirit, in the sense that you have grasped the idea, even if the path that got you there has a few errors.

 

[MikeeMiracle]

Thank you for the answers