The formation of massive Pop III stars in the presence of turbulence

TL;DR

This study uses high-resolution simulations to explore the formation and fragmentation of the first massive Population III stars, revealing disk formation, accretion rates, and potential for high stellar masses up to 100 solar masses.

Contribution

First high-resolution Eulerian grid-based simulations showing disk formation and fragmentation in Pop III star formation, highlighting turbulence effects on protostellar disk stability.

Findings

Disk forms around the first clump in primordial halos.

Central protostar can reach 40-100 solar masses.

Fragmentation occurs at larger scales in some halos.

Abstract

Population III stars forming in the infant universe at z=30 heralded the end of the cosmic dark ages. They are presumed to be assembled in so-called minihaloes with virial temperatures of a few thousand K where collapse is triggered by molecular hydrogen cooling. A central question concerns their final masses, and whether fragmentation occurs during their formation. While studies employing Lagrangian codes suggest fragmentation via a self-gravitating disk, recent high resolution simulations indicated that disk formation is suppressed. Here we report the first high-resolution large-eddy simulations performed with the Eulerian grid-based code Enzo following the evolution beyond the formation of the first peak, to investigate the accretion of the central massive clump and potential fragmentation. For a total of 3 halos, we see that a disk forms around the first clump. The central clump reaches $\sim10$ solar masses after 40 years, while subsequent accretion is expected at a rate of $10^{-2}$ solar masses per year. In one of these halos, additional clumps form as a result of fragmentation which proceeds at larger scales. We note that subgrid-scale turbulence yields relevant contributions to the stability of the protostellar disks. We conclude that the first protostar may reach masses up to $\rm 40-100 M_{\odot}$, which are only limited by the effect of radiative feedback.