New simulations are providing the most realistic pictures yet of how galaxies formed and evolved from the beginning of time.
The COLIBRE ‘virtual universe’ simulations have successfully reproduced many observed properties of real galaxies, both in the present-day Universe and in the early Universe, as seen by the James Webb Space Telescope (JWST).
These simulations confirm that the standard model of the Universe can explain galaxy formation more accurately than previously thought.
The simulations open up powerful new ways to compare theory with observations and explore a virtual universe through visuals, sound and interactive tools.
Our physicists wrote key elements of the software used for the simulations and helped run them on the DiRAC’s COSMA 8 supercomputer which is housed at Durham.
They are also leading major subprojects analysing the simulation results and comparing them to observed data.
Whilst observations give a snapshot in time, simulations allow physicists to better understand how objects in the early Universe are related to those we observe today.
COLIBRE is the first large-volume simulation to successfully model the cold gas and cosmic dust inside galaxies. These are the raw materials from which stars form and which shape how galaxies appear through telescopes.
Previous simulations did not model gas inside galaxies with temperatures below about 10,000 degrees, which is hotter than the surface of the Sun. This is because modelling this colder gas was too complex. Yet observations show that stars form in clouds of cold gas.
COLIBRE has been developed to be able to include the additional physical and chemical processes needed to model this cold interstellar gas directly.
It also simulates small dust grains that can greatly influence galactic gas.
Advances in algorithms and supercomputing enable COLIBRE to use up to 20 times more resolution elements than earlier simulations, allowing larger volumes to be simulated in greater detail and with better statistics.
Beyond traditional data, the team has also developed new ways to explore the simulations. This includes “sonified videos”, where sound encodes additional physical information, as well as interactive maps that allow users to explore the virtual universes.
The hope is that these new tools can help make the complex astronomy more accessible and engage audiences in new ways.
The team behind COLIBRE argue that it shows that realistic treatments of cold gas, dust, and outflows driven by stars and black holes are crucial for understanding galaxy evolution.
However, not everything is explained yet. The enigmatic “Little Red Dots” in the early Universe discovered by JWST, which may be the seeds of supermassive black holes, are not predicted by COLIBRE.
COLIBRE assumes that these seeds already exist. Modelling their formation will require even higher-resolution simulations and new physics - pointing the way for future work.
It is exhilarating to see “galaxies'' come out of our computer that look indistinguishable from the real thing and share many of the properties that astronomers measure in real data such as their number, luminosities, colours and sizes. I like to tease my observer colleagues by asking “Which galaxy catalogue do you think these images came from?'' What is most remarkable is that we are able to produce this synthetic universe purely by solving the relevant equations of physics in the expanding universe.
Visual impression of the COLIBRE simulations showing so-called cosmic web in the largest simulation.
Visual impression of one of the galaxies formed in the COLIBRE simulations, seen side-on.
Visual impression of the galaxies formed in the COLIBRE simulations, seen face-on.
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