Gravitational Collapse and Star Formation in Logotropic and Nonisothermal Spheres

摘要

We present semianalytical similarity solutions for the inside out, expansion-wave collapse of initially virialized gas clouds with nonisothermal equations of state. Results are given for the family of negative- index polytropes (P∝ρ~γ γ≤1), but we focus especially on the so-called logotrope, P/Pc = 1 + Aln(ρ/ρ_c). In a separate paper, we have shown this to be the best available phenomenological description of the internal structure and average properties of molecular clouds, as well as dense clumps of both high and low mass.