This set of images shows the distribution of the dark matter, obtained from a numerical simulation, at a redshift z~2, or when the Universe was about 3 billion years old.
The left panel displays the continuous distribution of dark matter particles, showing the typical wispy structure of the cosmic web, with a network of sheets and filaments that developed out of tiny fluctuations in the early Universe.
The central panel provides a simplified view of the complex network of dark matter structure according to the so-called halo model, a statistical approach used to describe the distribution of dark matter on both large and small scales. Within this framework, the dark matter distribution is viewed as an ensemble of discrete objects, the dark matter halos, corresponding to the densest knots of the cosmic web.
The right panel highlights the dark matter halos (shown in yellow) that represent the most efficient cosmic sites for the formation of galaxies. Only halos with a mass above a certain threshold can trigger the ignition of intense bursts of star formation, thus creating a starburst galaxy. According to the latest measurements achieved with Herschel, the minimum mass needed by a halo for a starburst galaxy to form within it is 3 x 10^11 times that of the Sun.