Royal Astronomical Society | 2016 Feb 24
[c][imghover=http://www.ras.org.uk/images/stories/pr ... 0small.png]http://www.ras.org.uk/images/stories/pr ... 0small.png[/imghover]A slab cut from the cube generated by the Illustris simulation. It shows theWe live in a universe dominated by unseen matter, and on the largest scales, galaxies and everything they contain are concentrated into filaments that stretch around the edge of enormous voids. Thought to be almost empty until now, a group of astronomers based in Austria, Germany and the United States now believe these dark holes could contain as much as 20% of the ‘normal’ matter in the cosmos and that galaxies make up only 1/500th of the volume of the universe. The team, led by Dr. Markus Haider of the Institute of Astro- and Particle Physics at the University of Innsbruck in Austria, publish their results in a new paper in Monthly Notices of the Royal Astronomical Society.
distribution of dark matter, with a width and height of 350 million light-years and a
thickness of 300000 light years. Galaxies are found in the small, white, high-density
dots. Mouse-over: The same slice of data, this time showing the distribution of
normal, or baryonic matter. (Credit: Markus Haider / Illustris Collaboration)[/c][hr][/hr]
Looking at cosmic microwave radiation, modern satellite observatories like COBE, WMAP and Planck have gradually refined our understanding of the composition of the universe, and the most recent measurements suggest it consists of 4.9% ‘normal’ matter (i.e., the matter that makes up stars, planets, gas and dust), or ‘baryons,’ whereas 26.8% is the mysterious and unseen ‘dark matter’, and 68.3% is the even more mysterious ‘dark energy’.
Complementing these missions, ground-based observatories have mapped the positions of galaxies and, indirectly, their associated dark matter over large volumes, showing that they are located in filaments that make up a ‘cosmic web.’ Haider and his team investigated this in more detail, using data from the Illustris project, a large computer simulation of the evolution and formation of galaxies, to measure the mass and volume of these filaments and the galaxies within them.
Illustris simulates a cube of space in the universe, measuring some 350 million light-years on each side. It starts when the universe was just 12 million years old, a small fraction of its current age, and tracks how gravity and the flow of matter changes the structure of the cosmos up to the present day. The simulation deals with both normal and dark matter, with the most important effect being the gravitational pull of the dark matter. ...
Large-Scale Mass Distribution in the Illustris-Simulation - Markus Haider et al
- Monthly Notices of the RAS 457(3):3024 (2016 Apr 11) DOI: 10.1093/mnras/stw077
arXiv.org > astro-ph > arXiv:1508.01525 > 06 Aug 2015
http://asterisk.apod.com/viewtopic.php?t=33377
http://asterisk.apod.com/viewtopic.php?t=33399