The Virgo Consortium

The SIBELIUS Project

Local Group analogue

A Local Group analogue from the SIBELIUS project.


Simulations Beyond the Local Universe (SIBELIUS) aims to recreate the galaxies and structures in the observed universe, using hybrid constrained initial conditions.

Most cosmological simulations, such as EAGLE or BAHAMAS, simulate structures in random periodic volumes, aimed at reproducing a statistically representative sample of the observed Universe. Zoom-in simulations , such as Apostle or Hydrangea, can refine subregions that resemble known structures, but by selecting regions from finite volumes, the resemblance is fundamentally limited.

In SIBELIUS, we use an alternative approach: Constrained initial conditions that represent the most likely initial state of the Universe, given the assumed cosmological model and the observed distribution of galaxies. We further take advantage of a hierarchical octree representation of the phase information to refine scales beyond the original constraints, to reproduce variants of the Local Universe over an unprecedented range of scales.

Large scale structure in SIBELIUS dark

The large scale structure in SIBELIUS dark compared to observations.


The initial paper for “The SIBELIUS Project” has been published as Sawala et al. 2022 and for the “SIBELIUS-DARK Project” as McAlpine et al. 2022. The SIBELIUS collaboration currently includes researchers in Helsinki, Durham, Leiden, Paris and Stockholm. For more information please contact Till Sawala.