Outflow Driven Turbulence in Molecular Clouds

TL;DR

This study uses 3D simulations to show that protostellar outflows can sustain turbulence in molecular clouds, producing a steeper velocity spectrum than isotropic forcing, with implications for understanding cloud dynamics.

Contribution

The paper demonstrates that outflows can effectively drive and sustain turbulence in molecular clouds, characterizing the resulting velocity spectrum and its differences from isotropic turbulence.

Findings

Turbulence can be sustained by outflow interactions.

Outflow driven turbulence produces a steeper velocity spectrum (beta ~ 3).

Comparison with isotropic turbulence shows different spectral slopes.

Abstract

In this paper we explore the relationship between protostellar outflows and turbulence in molecular clouds. Using 3-D numerical simulations we focus on the hydrodynamics of multiple outflows interacting within a parsec scale volume. We explore the extent to which transient outflows injecting directed energy and momentum into a sub-volume of a molecular cloud can be converted into random turbulent motions. We show that turbulence can readily be sustained by these interactions and show that it is possible to broadly characterize an effective driving scale of the outflows. We compare the velocity spectrum obtained in our studies to that of isotropically forced hydrodynamic turbulence finding that in outflow driven turbulence a power law is indeed achieved. However we find a steeper spectrum (beta ~ 3) is obtained in outflow driven turbulence models than in isotropically forced simulations (beta ~ 2). We discuss possible physical mechanisms responsible for these results as well and their implications for turbulence in molecular clouds where outflows will act in concert with other processes such as gravitational collapse.