Stuart McAlpine, John Helly, Matthieu Schaller, Till Sawala, Guilhem Lavaux, Jens Jasche, Carlos Frenk, Adrian Jenkins, John Lucey and Peter Johansson

Monthly Notices of the Royal Astronomical Society, 2022, tmp.348M

Over the past thirty years cosmologists have developed a standard model of cosmology — Lambda Cold Dark Matter (LCDM) which explains a plethora of astronomical data, from the properties of the microwave background radiation (the heat left over from the Big Bang) to the number and spatial distribution of galaxies in the Universe. Computer simulations lie at the heart of this development: they allow predictions to be made of the distribution of dark matter and galaxies, especially in the non-linear regime, the best observed.

Cosmological simulations usually follow a “typical” patch of a LCDM Universe. But the simulations of the Sibelius project are different: using advanced statistical techniques, they are conditioned to reproduce, by the present day, the structures that we see in the local universe, specifically in the 2MASS+ galaxy survey.

The volume simulated in Sibelius is a sphere around us of radius 200 Mpc. Galaxies in this dark matter-only simulation are followed with the semi-analytic galaxy formation model GALFORM. Structures familiar to astronomers, such as the Virgo, Coma and Perseus clusters of galaxies, the “Great Wall” and the “Local Void” — our cosmic habitat – emerge from LCDM initial conditions and are faithfully reproduced in the simulation. At the centre there is a pair of galaxies, the virtual counterparts of our own Milky Way and our massive neighbour, the Andromeda galaxy. Sibelius enables novel tests of LCDM and of galaxy formation theory. In addition it offers the possibility of studying in detail the formation paths and physical properties of objects such as the galaxy clusters in our local neighbourhood.

Left: dark matter distribution in a 50x50x50 Mpc region centred on the Milky Way, coloured by the projected density and velocity dispersion of the particles. Our two most massive neighbours, the Virgo cluster and the Fornax/Eridanus groups, are highlighted. Middle and right: zooms into a 15x15x15 Mpc and 5x5x5 Mpc regions, respectively. The right panel highlights the location of the Milky Way and Andromeda (M31). Images are shown in 𝑦–𝑧 equatorial coordinates, projected down the 𝑥 axis.
Categories: 2021 Highlights