Left: surface density of the circumstellar disk at the time at which the intruder is added to the simulation. Only the region inside 1000 AU from the central star is shown. The green and red arrows show the forming and already formed fragments in the disk. Middle: red contour lines show the regions with the Toomre Q-parameter smaller than unity, while the gray-shaded area indicated the disk regions where the Gammie -parameter is smaller than 3. Right: ratio N_Jeans (in log scale) of the Jeans length R_J to the maximum size of the local grid cell max(Δr,rΔφ). The minimum value of N_Jeans is found in the center of the contracting overdensity and is equal to five. In other parts of the contracting overdensity, N_Jeans is about ten, which means the Truelove criterion is fulfilled.