Formation of population III stars and pregalactic evolution

We discuss the formation and evolution of the first generation of stars (Population III) on the assumption that primordial fluctuations had an isothermal component. Immediately after recombination the scale of non-linearity would be |10^68 M_| and clouds of this mass would separate from the comoving frame. Prior to their collapse they would gain angular momentum due to tidal torques. We discuss the reasons why fragmentation is unlikely before centrifugal forces halt the collapse and dense disc forms. The disc will form initially at 104 K but small amount of H2 forming there will cool it to 1000 K, permitting fragmentation into masses as low as ≲|0. 2M|⁠. Later two-body interactons between these low-mass protostars would thicken the disc; after it has ‘sphericalized’ evaporation of stars from the system begins. When most have evaporated, the core of stars which remain in a gravitationally bound system will reach a collisional regime, and a very massive object (VMO) will form. According to this ‘scenario’, most of the hidden mass could be in very low mass stars (which would now generally have ‘evaporated’ from the tightly bound |10^6-8M_| clusters in which they formed), but a small percentage of the mass would be in VMOs. Cosmological implications of the model are discussed.