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In the cave
The geography of galaxies

The image from the CRAL presented here is mysterious and could be interpreted in various different ways. Some might see it as a nocturnal map of the sky with city lights to the forefront while others might suppose it portrays neural networks. However the image actually comes from the field of astrophysics and shows a simulation of a given volume of the universe and, to be more precise, how matter is distributed on a very large scale throughout the universe.

Simulation of a given volume of the universe showing the very large scale distribution of gases. Credits: © Léo Michel-Dansac (CRAL & LabEx LIO)

Imagine that you are looking at a road map rather than a galaxy. The pathways you can see are in reality filaments which link galaxies and can be defined as "gas-absorbing, star-producing machines". Finally, the place where no filaments pass is the vacuum, a kind of intergalactic countryside. Gas circulates along these filament axes and plays an essential role by 'feeding' galaxies. These filaments of gas are the main elements in these images and are coloured artificially using different shades which highlight their properties such as the heat or density of the gas involved. Around the galaxies which are forming, we can also see star explosions, portrayed here by little pink bubbles.

The videos show a rotating disk which resembles an incandescent flame to some extent and actually illustrates the structuring of gases within a galaxy in the regions known as spiral arms where stars form. The colours are artificial but symbolize the density of the gases present.

These images have been extracted from digital simulations produced using a supercomputer and give us an insight into researchers' work. This involves measuring the physical properties (density, flow, temperature, etc.) of the gases on these filaments to better understand how and in what form these gases are absorbed by galaxies. These measurements are then used to develop and refine a theory on the formation and evolution of galaxies.

Thanks to Léo Michel-Dansac for his contribution.

Simulation of a given volume of the universe which illustrates the effect of star explosions on the ejection of gas (portrayed by little pink bubbles) around galaxies which are forming. Credits: © Léo Michel-Dansac (CRAL & LabEx LIO)

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