POPULATION III STARS FROM TURBULENT FRAGMENTATION AT REDSHIFT ∼11

We report results from a cosmological simulation with non-equilibrium chemistry of 21 species, including H-2, HD, and LiH molecular cooling. Starting from cosmological initial conditions, we focus on the evolution of the central 1.8 kpc region of a 3 x 10(7) M-circle dot halo. The crossing of a few 10(6) M-circle dot halos and the gas accretion through larger scale filaments generate a turbulent environment within this region. Due to the short cooling time caused by the non-equilibrium formation of H2, the supersonic turbulence results in a very fragmented mass distribution, where dense, gravitationally unstable clumps emerge from a complex network of dense filaments. At z = 10.9, we find approximately 25 well-defined, gravitationally unstable clumps, with masses of 4 x 10(3)-9 x 10(5) M-circle dot, temperatures of approximately 300 K, and cooling times much shorter than the free-fall time. Only the initial phase of the collapse of individual clumps is spatially resolved in the simulation. Depending on the density reached in the collapse, the estimated average Bonnor-Ebert masses are in the range 200-800 M-circle dot. We speculate that each clump may further fragment into a cluster of stars with a characteristic mass in the neighborhood of 50 M-circle dot. This process, in halos of mass similar to 10(7) M-circle dot at z approximate to 11, may represent the dominant mode of Population III star formation, causing a rapid chemical enrichment of the protogalactic environment.