Cosmic vorticity and the origin of halo spins

Understand

In the standard model of cosmology, structure emerges out of non-rotational flow and the angular momentum of collapsing halos is induced by tidal torques.

• The growth of halo angular momentum in the linear and quasi-linear phases is associated with a shear, curl-free, flow and it is well described within the linear framework of tidal torque theory (TTT).
• However, TTT is rendered irrelevant as haloes approach turn around and virialization.
• At that stage the flow field around halos has non-zero vorticity.