Driven and Decaying Turbulence Simulations of Low-Mass Star Formation: From Clumps to Cores to Protostars

TL;DR

This study uses high-resolution simulations to compare driven and decaying turbulence in molecular clouds, revealing differences in protostellar system formation and properties, with implications for understanding star formation processes.

Contribution

It provides the first detailed high-resolution simulations comparing driven and decaying turbulence effects on star formation, including core properties and protostellar system development.

Findings

Decaying turbulence leads to high-multiplicity protostellar systems.

Driven turbulence results in smaller, fewer low-mass protostars.

Some differences in brown dwarf formation and core rotation were observed.

Abstract

Molecular clouds are observed to be turbulent, but the origin of this turbulence is not well understood. As a result, there are two different approaches to simulating molecular clouds, one in which the turbulence is allowed to decay after it is initialized, and one in which it is driven. We use the adaptive mesh refinement (AMR) code, Orion, to perform high-resolution simulations of molecular cloud cores and protostars in environments with both driven and decaying turbulence. We include self-gravity, use a barotropic equation of state, and represent regions exceeding the maximum grid resolution with sink particles. We analyze the properties of bound cores such as size, shape, linewidth, and rotational energy, and we find reasonable agreement with observation. At high resolution, the different rates of core accretion in the two cases have a significant effect on protostellar system development. Clumps forming in a decaying turbulence environment produce high-multiplicity protostellar systems with Toomre-Q unstable disks that exhibit characteristics of the competitive accretion model for star formation. In contrast, cores forming in the context of continuously driven turbulence and virial equilibrium form smaller protostellar systems with fewer low-mass members. Our simulations of driven and decaying turbulence show some statistically significant differences, particularly in the production of brown dwarfs and core rotation, but the uncertainties are large enough that we are not able to conclude whether observations favor one or the other.