Researchers from Durham’s Institute for Computational Cosmology (ICC) have developed a lifelike computer simulation of the universe in order to study the formation and evolution of star systems.
In collaboration with astrophysicists from the University of Leiden and other institutions, they built a virtual cosmos called EAGLE (Evolution and Assembly of Galaxies and their Environments) and ran it for several months on two supercomputers – COSMA, part of DiRAC-2, in Durham and CURIE in Paris. The resultant galaxies were found to have size, mass, shape and age consistent with observations of real galaxies, marking the first time a computer has generated galaxies with realistic properties.
EAGLE’s success has been attributed to the incorporation of galactic winds stronger than those used in previous models. Resulting from supernova explosions, supermassive black holes and winds from massive stars, these fast streams of particles move the gas responsible for star formation around, and can expel it completely from galaxies. With less material to amass, stars are lighter and it takes them longer to develop.
However there were many other factors which the team, led by Leiden’s Joop Schaye, had to correctly embody in the simulation in order to get a realistic result.
Dark matter is an essential component in the formation of galaxies; it contributes greatly to the galactic mass which in turn increases the strength of the gravitational force that causes clouds of gas and dust to collapse inwards. Consequently it was vital that Schaye et al. input an accurate value for the density of dark matter, as well as the density of baryonic (‘ordinary’) matter.
Also critical is the cosmological constant, which governs the amount of dark energy in space, or, in other words, the acceleration of the expansion of the universe.
They estimated these parameters using Cosmic Microwave Background (CMB) data taken by the European Space Agency’s Planck Satellite.
EAGLE is one of the largest hydrodynamical simulations of the universe to be made to date, employing 6.8 billion particles following the current standard cosmological model, Lambda Cold Dark Matter, to replicate conditions in the universe from its beginning 13.8 billion years ago to the current day with unparalleled accuracy.
It contains over 10,000 galaxies of the size of our own galaxy, the Milky Way, or bigger, in a virtual cube with sides of length 100 Megaparsecs (330 million light-years).
“The universe generated by the computer is just like the real thing,” said Professor Richard Bower, member of the ICC and one of the scientists working on the EAGLE Project.
“There are galaxies everywhere, with all the shapes, sizes and colours I’ve seen with the world’s largest telescopes.”
Schaye, Bower and the other researchers behind EAGLE are using the simulation to understand not only how galaxies from but how their properties are determined by the balance between feedback, star formation and black hole accretion – where black holes accumulate nearby matter through gravitational attraction.
Their latest results were published in the journal Monthly Notices of the Royal Astronomical Society at the start of January.
Image: EAGLE Project / Richard Bower / Josh Borrow