On the contraction of protostellar clouds with different metallicities

We examine the thermal and chemical evolution of gravitationally collapsing protostellar clouds with metallicity 0 ≤ Z/Z_⊙ ≤ 1. During the first collapse stage, the temperatures are higher for lower metallicity clouds. However, in the course of the adiabatic contraction of transient cores, the evolutionary trajectories of the clouds converge to a curve that is determined only by fundamental physical constants. The trajectories coincide each other thereafter. The size of the stellar core at formation is the same regardless of metallicity.