The fragmentation process of primordial-gas cores during prestellar collapse is studied using three-dimensional nested-grid hydrodynamics. Starting from the initial central number density of nc ∼ 103 cm-3, we follow the evolution of rotating spherical cores up to the stellar density nc ≃ 1022 cm-3. An initial condition of the cores is specified by three parameters: the ratios of the rotation and thermal energies to the gravitational energy ( β0 and α0, respectively), and the amplitude of the bar-mode density perturbation (AΦ). Cores with rotation β0 > 10-6 are found to fragment during the collapse. The fragmentation condition hardly depends on either the initial thermal energy α0 or amplitude of bar-mode perturbation AΦ. Since the critical rotation parameter for fragmentation is lower than that expected in first-star formation, binaries or multiples are also common for the first stars.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science