Can Protostellar Jets Drive Supersonic Turbulence in Molecular Clouds?

TL;DR

This study uses multi-dimensional jet simulations to assess whether protostellar jets can generate and sustain supersonic turbulence in molecular clouds, finding they mainly produce subsonic motions and do not sustain turbulence far from the jet.

Contribution

It provides detailed simulation analysis showing collimated jets do not drive widespread supersonic turbulence, challenging previous assumptions about their role in molecular cloud dynamics.

Findings

Jets do not excite supersonic motions far from the jet.

Supersonic fluctuations are quickly damped and confined near the jet.

Jets can disrupt dense clumps but do not sustain turbulence in the cloud.

Abstract

Jets and outflows from young stellar objects are proposed candidates to drive supersonic turbulence in molecular clouds. Here, we present the results from multi-dimensional jet simulations where we investigate in detail the energy and momentum deposition from jets into their surrounding environment and quantify the character of the excited turbulence with velocity probability density functions. Our study include jet--clump interaction, transient jets, and magnetised jets. We find that collimated supersonic jets do not excite supersonic motions far from the vicinity of the jet. Supersonic fluctuations are damped quickly and do not spread into the parent cloud. Instead subsonic, non-compressional modes occupy most of the excited volume. This is a generic feature which can not be fully circumvented by overdense jets or magnetic fields. Nevertheless, jets are able to leave strong imprints in their cloud structure and can disrupt dense clumps. Our results question the ability of collimated jets to sustain supersonic turbulence in molecular clouds.