Solving the puzzle of subhalo spins
  Investigating the spin parameter distribution of subhaloes in two high
resolution isolated halo simulations, re- cent work by Onions et al. suggested
that typical subhalo spins are consistently lower than the spin distribution
found for field haloes. To further examine this puzzle, we have analyzed
simulations of a cosmological volume with sufficient resolution to resolve a
significant subhalo population. We confirm the result of Onions et al. and show
that the typical spin of a subhalo decreases with decreasing mass and
increasing proximity to the host halo center. We interpret this as the growing
influence of tidal stripping in removing the outer layers, and hence the higher
angular momentum particles, of the subhaloes as they move within the host
potential. Investigating the redshift dependence of this effect, we find that
the typical subhalo spin is smaller with decreasing redshift. This indicates a
temporal evolution as expected in the tidal stripping scenario.
