Spin flips I: Evolution of the angular momentum orientation of Milky Way-mass dark matter haloes

Understand

During the growth of a cold dark matter halo, the direction of its spin can undergo rapid changes.

• These could disrupt or even destroy a stellar disc forming in the halo, possibly resulting in the generation of a bulge or spheroid.
• We investigate the frequency of significant changes in the orientation of the angular momentum vector of dark matter haloes ("spin flips"), and their degree of correlation with mergers.
• We focus on haloes of mass similar to that of the Milky Way (MW) halo at redshift z=0 (log M/(Msol/h) = 12.0 to 12.5) and consider flips in the spin of the whole halo or just its inner parts.