Resolving infall caustics in dark matter halos
  We have found that the phase-space of a dark matter particles assembling a galactic halo in cosmological N-body simulations has well defined fine grained structure. Recently accreted particles form distinctive velocity streams with high density contrast. For fixed observer position these streams lead to peaks in velocity distribution. Overall structure is close to that emerging in the secondary infall model. 
K. Dolag, A. D. Dolgov and I. I. Tkachev
astro-ph.GA hep-ph