On the Segregation of Dark Matter Substructure
  We present the first comprehensive analysis of the segregation of dark matter
subhaloes in their host haloes. Using numerical simulations, we examine the
segregation of twelve different subhalo properties with respect to both orbital
energy and halo-centric radius (in real space as well as in projection).
Subhaloes are strongly segregated by accretion redshift, which is an outcome of
the inside-out assembly of their host haloes. Since subhaloes that were
accreted earlier have experienced more tidal stripping, subhaloes that have
lost a larger fraction of their mass at infall are on more bound orbits.
Subhaloes are also strongly segregated in their masses and maximum circular
velocities at accretion. We demonstrate that part of this segregation is
already imprinted in the infall conditions. For massive subhaloes it is
subsequently boosted by dynamical friction, but only during their first radial
orbit. The impact of these two effects is counterbalanced, though, by the fact
that subhaloes with larger accretion masses are accreted later. Because of
tidal stripping, subhaloes reveal little to no segregation by present-day mass
or maximum circular velocity, while the corresponding torques cause subhaloes
on more bound orbits to have smaller spin. There is a weak tendency for
subhaloes that formed earlier to be segregated towards the center of their host
halo, which is an indirect consequence of the fact that (sub)halo formation
time is correlated with other, strongly segregated properties. We discuss the
implications of our results for the segregation of satellite galaxies in galaxy
groups and clusters.
