Rotation and Internal Structure of Population III Protostars

TL;DR

This study uses cosmological simulations to show that Population III protostars form with high rotational support, maintaining rapid rotation through early evolution, which impacts their subsequent development and explosive phenomena.

Contribution

First self-consistent simulation resolving the rotation and internal structure of Pop III protostars, revealing high rotational support persists during early stages.

Findings

Pop III protostars form with ~50-100% of Keplerian rotation.

Protostars show little convective instability in early stages.

Rotation rates are maintained after multiple mergers.

Abstract

We analyze the cosmological simulations performed in the recent work of Greif et al. (2012), which followed the early growth and merger history of Pop III stars while resolving scales as small as 0.05 R_sol. This is the first set of cosmological simulations to self-consistently resolve the rotation and internal structure of Pop III protostars. We find that Pop III stars form under significant rotational support which is maintained for the duration of the simulations. The protostellar surfaces spin from ~50% to nearly 100% of Keplerian rotational velocity. These rotation rates persist after experiencing multiple stellar merger events. In the brief time period simulated (~ 10 yr), the protostars show little indication of convective instability, and their properties furthermore show little correlation with the properties of their host minihaloes. If Pop III protostars within this range of environments generally form with high degrees of rotational support, and if this rotational support is maintained for a sufficient amount of time, this has a number of crucial implications for Pop III evolution and nucleosynthesis, as well as the possibility for Pop III pair-instability supernovae, and the question of whether the first stars produced gamma-ray bursts.