SIMBAD references

We discuss fragmentation processes which induce star formation in the dense walls of expanding shells. We test the influence of the energy input, the interstellar medium scaleheight and the speed of sound in the ambient medium, and formulate the condition for the gravitational fragmentation of expanding shells: if the total surface density of the disc is higher than a certain critical value, the shells are unstable. The value of the critical density depends on the energy of the shell and the sound speed in the interstellar medium.