Formation of satellites from cold collapse
  We study the collapse of an isolated, initially cold, irregular (but almost
spherical) and (slightly) inhomogeneous cloud of self-gravitating particles.
The cloud is driven towards a virialized quasi-equilibrium state by a fast
relaxation mechanism, occurring in a typical time $\tau_c$, whose signature is
a large change in the particle energy distribution. Post-collapse particles are
divided into two main species: bound and free, the latter being ejected from
the system. Because of the initial system's anisotropy, the time varying
gravitational field breaks spherical symmetry so that the ejected mass can
carry away angular momentum and the bound system can gain a non-zero angular
momentum. In addition, while strongly bound particles form a compact core,
weakly bound ones may form, in a time scale of the order of $\tau_c$, several
satellite sub-structures. These satellites have a finite lifetime that can be
longer than $\tau_c$ and generally form a flattened distribution. Their origin
and their abundance are related to the amplitude and nature of initial density
fluctuations and to the initial cloud deviations from spherical symmetry, which
are both amplified during the collapse phase. Satellites show a time dependent
virial ratio that can be different from the equilibrium value $b\approx -1$:
although they are bound to the main virialized object, they are not necessarily
virially relaxed.
