Our new formulation of the Spherical Collapse Model (SCM-L) takes into account the presence of angular momentum associated with the motion of galaxy groups infalling towards the centre of galaxy clusters. The angular momentum is responsible for an additional term in the dynamical equation which is useful to describe the evolution of the clusters in the non-equilibrium region which is investigated in the present paper. Our SCM-L can be used to predict the profiles of several strategic dynamical quantities as the radial and tangential velocities of member galaxies, and the total cluster mass.
A good understanding of the non-equilibrium region is important since it is the natural scenario where the infall in galaxy clusters and the accretion phenomena present in these objects can be studied. Our results corroborate previous estimates and are in very good agreement with the analysis of recent observations and of simulated clusters.