The universal nature of subhalo accretion
  We examine the angular infall pattern of subhaloes onto host haloes in the
context of the large-scale structure. We find that this infall pattern is
essentially driven by the shear tensor of the ambient velocity field. Dark
matter subhaloes are found to be preferentially accreted along the principal
axis of the shear tensor which corresponds to the direction of weakest
collapse. We examine the dependence of this preferential infall on subhalo
mass, host halo mass and redshift. Although strongest for the most massive
hosts and the most massive subhaloes at high redshift, the preferential infall
of subhaloes is effectively universal in the sense that its always aligned with
the axis of weakest collapse of the velocity shear tensor. It is the same shear
tensor that dictates the structure of the cosmic web and hence the shear field
emerges as the key factor that governs the local anisotropic pattern of
structure formation. Since the small (sub-Mpc) scale is strongly correlated
with the mid-range (~10 Mpc) scale - a scale accessible by current surveys of
peculiar velocities - it follows that findings presented here open a new window
into the relation between the observed large scale structure unveiled by
current surveys of peculiar velocities and the preferential infall direction of
the Local Group. This may shed light on the unexpected alignments of dwarf
galaxies seen in the Local Group
