Particle energy distribution of the QSS at t = 9 Gyr in units of e₀ (see Eq. (4)). The system after the collapse is made of three components: two form the QSS (tail and core) and the third, where e >  0, is made of “free” particles. The core is comprised of particles with radial distance r <  r₀; the free particles have positive energy or r >  r_f, where r_f = r_f(t) must be estimated from the numerical data.