This month’s media comes from PhD student Ruby Wright from our node at the University of Western Australia (UWA). Ruby presents her recent simulation results on how dark matter (DM) and gas clump together using data from the EAGLE suite of hydrodynamical simulations.

Below is an illustration of the gas in and around a group-sized dark matter halo from the EAGLE hydrodynamical simulations. A group sized halo holds the same amount of material as 100 million million Suns! This kind of region will hold several galaxies. In the image, the blue gas particles are those falling onto the halo (otherwise known as “accreting”) for the first time, and the grey gas particles are those that have previously accreted onto the halo and now form part of it.

The distribution of simulated gas as it accretes onto a DM halo. Left: Grey represents gas particles already part of the halo 2.21 billion years ago, blue represents gas that is accreting onto the halo. There is the equivalent mass of 169 million million times our Sun within the halo. Right: All gas from left image has accreted onto the halo 900 million years later (or 1.31 million years ago). The halo has accreted the equivalent of 17 million million Suns over that time, including both dark matter and gas.

In the left image, there are obvious filament-like structures which trace what’s known as the Cosmic Web – the structure of DM and gas on very large scales, and it’s down these filaments that the gas is accreted onto the halo.

The two images represent the same simulated halo at different times in the history of the Universe. The left is how the halo and gas looked 2.21 billion years ago where the right is 1.31 billion years ago. The 900 million years between these two snapshots saw the successful accretion of the blue particles into the halo.

The aim of this work is to understand how galaxies are “fed” with the gas which eventually allows them to form stars.