The role of turbulence, magnetic fields and feedback for star formation

TL;DR

This paper uses high-resolution simulations to investigate how turbulence, magnetic fields, and feedback collectively regulate star formation rates in molecular clouds, aligning with observed low efficiencies.

Contribution

It demonstrates that simultaneous inclusion of turbulence, magnetic fields, and feedback is essential to reproduce realistic star formation rates in simulations.

Findings

Simulations with all three processes match observed star formation rates.

Turbulence, magnetic fields, and feedback are collectively crucial for star formation regulation.

Without all three, simulated star formation rates are too high.

Abstract

Star formation is inefficient. Only a few percent of the available gas in molecular clouds forms stars, leading to the observed low star formation rate (SFR). The same holds when averaged over many molecular clouds, such that the SFR of whole galaxies is again surprisingly low. Indeed, considering the low temperatures, molecular clouds should be highly gravitationally unstable and collapse on their global mean freefall timescale. And yet, they are observed to live about 10-100 times longer, i.e., the SFR per freefall time is only a few percent. Thus, other physical mechanisms must provide support against quick global collapse. Magnetic fields, turbulence and stellar feedback have been proposed as stabilising agents controlling star formation, but it is still unclear which of these processes is the most important and what their relative contributions are. Here I present high-resolution, adaptive-mesh-refinement simulations of star cluster formation that include turbulence, magnetic fields, and protostellar jet/outflow feedback. These simulations produce nearly realistic star formation rates consistent with observations, but only if turbulence, magnetic fields and feedback are included simultaneously.