The Virgo Consortium

The COCO Project

Projected density along the z-axis.

Projected density along the z-axis of a 70.4×70.4×1.5 Mpc/h slice centred on the middle of the COCO simulation at redshift z = 0.


The Copernicus Complexio (or COCO) simulations aim to replicate the observed universe with over 13 billion particles in a supercomputer to gain insight into one of the most fundamental questions in science: “Is the Milky Way unique? And if so, why?”.

Cold dark matter (CDM) has long been the standard dark matter candidate, and has done an excellent job in matching real observations of the universe.

However, particle physicists tell us that there could be a different kind of particle, known as a sterile neutrino , which would constitute warm dark matter (WDM), in which the particles move much faster in the early universe.

The two models make different predictions for the nature of structure formation in the universe, with fewer low-mass haloes (the gravitational sinks in which galaxies form) being created in WDM. COCO simulates WDM and CDM cosmologies to test the differences between the two.

BAHAMAS light cone maps

Projected density map in a slice of dimensions (70.4 × 70.4 × 1.5) Mpc/h centred on the COCO high resolution region at z = 0. The side panels show zooms of a sample of haloes identified at z = 0, matched between COCO-WARM (left) and COCO-COLD (right).


The initial paper for “The COCO Project” has been published as Hellwing et al. 2015. For more information please visit ICM’s project description page or contact Wojciech Hellwing.