Star Formation Regulation: Understanding the Role of Galactic-Scale Turbulence via its Self-Consistent Cascade – CASCADE

One of the major questions of galaxy evolution is: why are galaxies so inefficient at forming stars? Indeed, we need to find a process opposing gravity, slowing down the conversion of gas to stars by a factor 100 compared to the free-fall time of the gas to understand how star formation is regulated.

All processes considered so far were shown to provide insufficient support against gravity. A missing process is supersonic turbulence, injected at galactic scales (10s of kpc) and cascading down to the scale of prestellar cores (~0.1 pc). Turbulence may provide the required support, and also modify the impact of other processes, such as star formation feedback. Understanding turbulence is thus primordial, but the huge cascade dynamic range involved was intractable for numerical simulations. To undo this lock, I developed an encapsulated-zoom method for numerical simulations.We are now able to simulate, for the first time self-consistently, the self-generated turbulence cascade over four decades in spatial scales, finally bridging the gap between galactic scales and prestellar cores.

To understand the role of galactic-scale turbulence, we will characterise the turbulence injection by each galaxy scale energy source (e.g disk instabilities) and determine turbulence’s interplay with the energy release from star formation feedback. We will account for the galactic environment and test our new understanding on Gyrs timescales. We will produce observable predictions of the footprint of star formation regulation by galactic scale turbulence to compare our results to the newest surveys. Furthermore, we will create models of the interaction between turbulence and stellar feedback, port our methods to emerging GPU codes, and produce predictions for the upcoming SKA and ELT.

Thanks to this methodology, we are now able to determine whether or not the self-consistent treatment of galactic-scale turbulence is sufficient to regulate star formation in galaxies.