Amplification of turbulence in contracting prestellar cores in primordial minihalos

TL;DR

This study demonstrates that gravitational contraction in primordial minihalos significantly amplifies turbulence, reaching sonic levels regardless of initial turbulence, which may influence star formation processes.

Contribution

The paper provides the first numerical and analytical analysis of turbulence amplification during primordial gas cloud collapse, highlighting its potential impact on star formation.

Findings

Turbulent velocity is amplified by gravitational contraction.

Amplification can reach sonic speeds even from low initial turbulence.

Numerical results agree with the derived analytical formula.

Abstract

We investigate the amplification of turbulence through gravitational contraction of the primordial gas in minihalos. We perform numerical simulations to follow the cloud collapse, assuming polytropic equations of state for different initial turbulent Mach numbers and resolutions. We find that the turbulent velocity is amplified solely by gravitational contraction, and eventually becomes comparable to the sound speed, even for small initial turbulent Mach numbers (${\cal M}_0 \gtrsim 0.05$). We derive an analytic formula for the amplification of turbulent velocity in a collapsing cloud, and find that our numerical results are consistent with the formula. These results suggest that the turbulence can play an important role in collapsing clouds for general cases.