Equilibria and dynamics of isothermal clouds

Recent studies of equilibrium structure and dynamical collapse and fragmentation of rotating isothermal clouds are described. Compared with a nonrotating case, the problem of a rotating cloud involves an additional degree of freedom, i.e., the distribution of specific angular momentum. Moreover, rotation can sustain a cloud with mass much greater than that of a spherical cloud. Nonspherical collapse with rotation gives rise to a flattened disk and, in the case of a very flattened disk, it forms one or more filaments which soon fragment into a number of small clouds. Results of two-dimensional and three-dimensional simulations of collapse and fragmentation of rotating isothermal clouds are presented.