Clumpy Structures within the Turbulent Primordial Cloud

This paper investigates the impact of turbulence on the formation of Population III (Pop~III) stars, the first stars in the universe that play a crucial role in cosmic evolution. Previous cosmological simulations of Pop~III star formation predicted a typical mass of around $\mathrm{ 100 \, M_\odot}$, which conflicts with recent observations of extremely metal-poor stars suggesting a lower mass scale of around $\mathrm{25 \, M_\odot}$. The discrepancy may arise from unresolved turbulence in the Pop~III star-forming cloud, driven by accreting primordial gas during mini-halo formation in the previous simulation. To examine this turbulence effect, we use the adaptive mesh refinement code $\texttt{Enzo}$ to model the Pop~III star-forming cloud, including artificial-driven turbulence and relevant gas physics. This artificial-driven turbulence uses a stochastic forcing model to mimic the unresolved turbulence inside mini-halos. Our results show that strong, compressive turbulence effectively fragments the cloud into several clumps, each with dense cores of $\mathrm{22.7 - 174.9 \, M_\odot}$ that undergo Jeans instability to form stars. With stronger and more compressive turbulence, more clumps are formed, suggesting that turbulence can decrease the theoretical mass scale of Pop~III stars and reconcile the mass discrepancy between simulations and observations.