Forming the First Stars in the Universe: The Fragmentation of Primordial Gas
Abstract
In order to constrain the initial mass function (IMF) of the first generation of stars (Population III), we investigate the fragmentation properties of metal-free gas in the context of a hierarchical model of structure formation. We investigate the evolution of an isolated 3-sigma peak of mass 2x106 Msolar which collapses at zcoll=30 using Smoothed Particle Hydrodynamics. We find that the gas dissipatively settles into a rotationally supported disk which has a very filamentary morphology. The gas in these filaments is Jeans unstable with MJ~103 Msolar. Fragmentation leads to the formation of high density (n>108 cm-3) clumps which subsequently grow in mass by accreting surrounding gas and by merging with other clumps up to masses of ~104 Msolar. This suggests that the very first stars were rather massive. We explore the complex dynamics of the merging and tidal disruption of these clumps by following their evolution over a few dynamical times.
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