  We study the collapse and virialization of an isolated spherical cloud of
self-gravitating particles initially at rest and characterised by a power-law
density profile, with exponent 0<= \alpha < 3, or by a Plummer, an Hernquist, a
NFW, a Gaussian profile. We find that in all cases the virialized structure
formed after the collapse has a density profile decaying, at large enough
radii, as ~ r^{-4}, and a radial velocity dispersion profile decaying as
~r^{-1}. We show that these profiles originate from the physical mechanism
responsible of the ejection of a fraction of cloud's mass and energy during the
collapse and that this same mechanism washes out the dependence on the initial
conditions. When a large enough initial velocity dispersion is given to the
cloud particles, ejection does not occur anymore and consequently the
virialized halo density and velocity profiles display features which reflect
the initial conditions.
