Astronomers use supercomputers to create their own Universe
Sen—Astronomers have used two powerful supercomputers to develop a simulation of the Universe in which realistic galaxies are created. It is designed to help them understand how galaxies form and evolve and how the Universe developed from almost 14 billion years ago until now.
EAGLE (Evolution and Assembly of GaLaxies and their Environments) is run by an international team of astronomers, based at the Universities of Leiden in the Netherlands, and Durham in the UK. It is the first hydrodynamical simulation, meaning it includes gas as opposed to only dark matter, that reproduces galaxies with mass, size and age similar to those of observed galaxies.
Galaxies that formed in previous simulations were often too massive, too small, too old and too spherical. The galaxies formed in the EAGLE-simulation are much closer to real galaxies thanks to the inclusion of strong galactic winds, which blow away the gas supply needed for the formation of stars.
In the simulation these galactic winds are stronger than in earlier simulations as EAGLE allows winds to develop naturally without predetermined speed or mass-loading factors.
Zooming into an EAGLE galaxy. Image credit: EAGLE Project Consortium
Professor Joop Schaye of Leiden University told Sen: "To achieve the match to observations, EAGLE required very strong galactic outflows. These intergalactic shock waves are powered by star formation and supermassive black holes. EAGLE tells us that galaxy formation is a violent process."
EAGLE's galaxies are lighter and younger because fewer stars form and they form later in each galaxy's development.
EAGLE is one of the largest cosmological simulations, containing 6.8 billion particles and requiring more than one and a half months of computer time on some of the world’s largest supercomputers, the "Cosmology Machine" in Durham and at "Curie" in Paris.
The simulation models the formation of structures in a cosmological volume, 100 Megaparsecs on a side (over 300 million light-years). It is large enough to contain 10,000 galaxies of the size of the Milky Way or bigger, enabling a comparison with the whole zoo of galaxies visible in the Hubble Deep field for example.
The classic Hubble sequence of galaxies as demonstrated with EAGLE. Image credit: EAGLE Project Consortium
Professor Schaye told Sen: "EAGLE naturally produces the diversity of real galaxies. Our virtual Universe contains dwarf as well as giant galaxies, ellipticals as well as spirals. We now have a tool that will help us understand the physical origin of this diversity."
Co-author of a paper on the study, Richard Bower from Durham University, said: "The Universe generated by the computer is just like the real thing. There are galaxies everywhere, with all the shapes, sizes and colours I've seen with the world's largest telescopes. It is incredible."
He told Sen: "We can use the simulations to understand how galaxies like our own are created and what is special about them. In the simulation we can pick an interesting galaxy and then press a button to make time run backwards and see where it came from."
Astronomers can now use the EAGLE simulation to study the evolution of individual galaxies in detail. "This is the start of a new era for us," said co-author Rob Crain from the UK's Liverpool John Moores University. "We can now manipulate the conditions of the Universe and study the evolution of galaxies throughout the past 14 billion years."