Toomre parameter Q_Toomre (red solid line) and τ_coolΩ (blue dotted line) as a function of semimajor axis a at a moment shortly after the beginning of disk evolution. The horizontal lines correspond to the critical values of Q_Toomre,crit = 1.7 and τ_coolΩ = 3, respectively. The left panel is for a disk with an initial mass M_d(t = 0) = 0.024   M_⊙, while the right one corresponds to a higher mass, M_d(t = 0) = 0.11   M_⊙.