Probable number of self-gravitating cores found within radius . Upper panel:Model I plotted with ϵ = 1 and for several values of the density envelope amplitude, A. Lower panel: Model II without thermal support for several values of the global cloud Mach number, . The circles mark the values where one self-gravitating core is found. In the range of our interest, that is, where equals a few, there is an almost linear dependance between and .