A realistic picture of how galaxies formed and evolved from the first billion years after the Big Bang to the present day has been revealed by new audio-visual simulations.
The COLIBRE simulations, created by an international team of researchers led by astronomers from Leiden University in the Netherlands, show the standard cosmological model can explain the observed growth of galaxies when key physics is included.
Dr Aaron Ludlow, from the International Centre for Radio Astronomy Research at The University of Western Australia, co-authored the study published in Monthly Notices of the Royal Astronomical Society.
Project leader Professor Joop Schaye, from Leiden University, said much of the gas inside real galaxies is cold and dusty.
"Most previous large simulations had to ignore this but with COLIBRE we could finally bring these essential components into the picture," Professor Schaye said.
By including these elements, the researchers created simulations that reproduced real galaxies, both in the present-day universe and in the early universe as seen by the James Webb Space Telescope.
"We've created new ways to compare theory with observations and to explore a virtual universe through visuals, sound and interactive tools," Dr Ludlow said.
Earlier simulations artificially prevented gas inside galaxies from cooling below about 10,000 degrees, hotter than the surface of the Sun – but observations show stars form in cold gas.
The COLIBRE simulations include the additional physical and chemical processes needed to model cold interstellar gas directly and also simulates small dust grains, that greatly influence galactic gas.
Dust particles help hydrogen molecules to form, which dominate the cold gas inside galaxies, shields gas from harsh ultraviolet radiation and strongly affects how galaxies appear in telescopes.
"Dust absorbs and scatters ultraviolet and optical light from stars and re-emits it in the infrared, affecting how galaxies appear in telescope images," Dr Ludlow said. "By modelling dust directly, we've found new ways to compare simulations with real data."
Advances in algorithms and supercomputing allowed COLIBRE to use up to 20 times more resolution elements than earlier simulations, allowing larger volumes to be simulated in greater detail.
"Our modelling demonstrates that realistic treatments of cold gas, dust, and outflows driven by stars and black holes are crucial for understanding galaxy evolution," Dr Ludlow said.
The simulations provide a powerful a new tool for testing theories, interpreting observations and creating "virtual observations" to check how astronomers analyse real data.
COLIBRE includes researchers from Leiden University, the universities of Durham, Portsmouth, Hull, Liverpool and Nottingham in the UK, University of Vienna in Austria, University of Milano-Bicocca in Italy, UWA, University of Ghent in Belgium and University of Pennsylvania in the US.
Images, videos and interactive material are available at: https://colibre.strw.leidenuniv.nl/
