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View submission: Why is the dark matter halo spherical?
It looks like others here have answered the question as to why DM halos are spherical but this is a great opportunity to share what I learned yesterday about cases where DM halos are NOT spherically symmetric! Simulations of barred spiral galaxies show that a stellar bar can be massive enough to have a significant torque on the DM halo. The dark matter actually forms a barred structure itself. The dark matter bar ends up being an important part of why the stellar bar gets destroyed as it evolves. In other words, the DM bar could be an important piece of the puzzle of how barred spirals become regular spirals. And here's a cool fact: If the halo spin is retrograde (opposite direction as the stars and gas), the DM bar forms perpendicular to the stellar bar! I thought this was totally amazing and new so I wanted to share :)
Here are some references:
https://arxiv.org/pdf/2105.04698.pdf[1][2]
1: https://arxiv.org/pdf/2105.04698.pdf
2: https://arxiv.org/pdf/2105.04698.pdf
https://arxiv.org/pdf/1811.00033.pdf[3][4]
3: https://arxiv.org/pdf/1811.00033.pdf
4: https://arxiv.org/pdf/1811.00033.pdf
There's nothing here!