PRACE: Zooming in on Star Formation

The PRACE project "Zooming in on Star Formation" has been running on the CURIE supercomputer for a one year period during 2014-2015 and was granted a total allocation of 10 Million core-hours. In this project page we are collecting and documenting the results from the project.

Project members:

Troels Haugbølle (PI), Søren Frimann, Troels Frostholm, Tommaso Grassi, Jes Jørgensen, Michael Küffmeier, Åke Nordlund, Paolo Padoan


Newborn stars, surrounded by centrifugally supported discs of gas and dust, reside in the central regions of hot cores, which are embedded in colder, extended envelopes. Above the discs and close to the star, outflows are launched in the form of winds and jets. These systems exist for a few million years during and after the birth of the star. In the early stages of this process, the envelope collapses under its own gravity, and a disc is quickly formed. By removing excess angular momentum and potential energy, this accretion disc functions as a conduit, which allows most of the gas and dust to either accrete onto the star or be lost in the outflows, while leaving a small fraction of the mass in the form of planets. Detailed modelling of the properties of proto-stellar systems is thus a prerequisite for understanding planet formation. Because of the small scale of the inner proto-planetary disc, relative to the distance of even the nearest star forming regions, very few detailed ? spatially resolved ? observations have been available in the past. The Herschel satellite and the new sub-millimeter facility ALMA are revolutionizing observational star formation. In particular, ALMA is currently providing many new observations of proto-stellar systems, and a more complex picture is emerging with e.g. warped discs containing intricate structures, such as large-scale dust devils, and many signs of newborn planets perturbing the gas and dust. Unravelling the physical processes at play is crucially important and requires modelling, and understanding, an intricate interplay between large-scale environmental factors, which regulate the supply of mass, angular momentum, and magnetic flux to the forming stars, and small-scale processes close to the star, which control the evolution and dynamics in the inner part of the envelope and proto-planetary disc. This proposal will encompass these disparate scales using extremely deep adaptive mesh refinement simulations, reaching a factor of a billion in linear resolution compared to the outer scales of the simulated domain. These unprecedented capabilities are complemented by a unique approach that we have developed to provide boundary conditions by embedding our model in to some of the largest models ever made of star forming regions. Using the CURIE supercomputer we will perform, for the first time ever, a systematic study that bridges the gap between molecular cloud scales, where magnetic fields are anchored and the initial and boundary conditions for proto-stellar accretion are set, and the much smaller disc and jet scales, which determine the ultimate evolution of proto-stellar systems. Because of the unique combination of methods and resources, this study will have a major impact in our global understanding of how stars and planets form.


Zoom-in models

Obtaining the main-aim of our project, we successfully carried out a campaign to make many zoom-in models of stars sampled from a much larger GMC-scale box. These simulations now form a unique library of models, which will be used in the future as the basis of a number of articles that study the in-fall and accretion of matter around the individual stars. As foreseen, not all stars are created equal, and the variety of systems give us for the first time varied but realistic insight in to the conditions that allowed for formation of low-mass stars, including our own solar system.


An important missing piece of physics in our models until now has been the thermodynamic description. By integrating the astro-chemistry framework KROME with our main simulation code RAMSES we got the opportunity to explore astro-chemistry in small-scale models of molecular clouds; this was not foreseen at time when we applied for the project. The models include H-C-O chemistry, driven turbulence, dust, a simple local prescription for radiative transfer, and magnetic fields, and will be the basis for a number of articles exploring the consequence of chemistry in to our models

Molecular clouds

Taking advantage of our CURIE allocation, we used a small fraction of the time to rerun a molecular cloud model describing a small 4 parsec molecular cloud with isothermal physics, a new optimised sink particle model, and magnetic fields. This model is the current culmination of a large number of simulations we have carried out over the years at both local and international HPC centers to understand and calibrate our current sink particle model. The resulting simulation - finished on local resources - is already used in a number of exciting projects, with one submitted article, and more to come.


Küffmeier, Michael; Frostholm Mogensen, Troels; Haugbølle, Troels; Bizzarro, Martin; Nordlund, Åke: "Tracking the distribution of 26Al and 60Fe during the early phases of star and disk evolution", Accepted by ApJ. URL:

Frimann, Søren; Jørgensen, Jes K.; Padoan, Paolo; Haugbølle, Troels: "Protostellar accretion traced with chemistry. Comparing synthetic C18O maps of embedded protostars to real observations", Astronomy & Astrophysics, Volume 587, id.A60. URL: