2024-02-22 11:00:26
In the last decade, astrophysicists have developed tools that allow them to simulate, with the help of supercomputers, how galaxies formed from the Big Bang, 13.8 billion years ago, to today. However, they have always been limited by various sources of error.
Now, an international research group, led by Ji-hoon Kim at Seoul National University (Korea), Joel Primack at the University of California at Santa Cruz in the United States, and Santi Roca-Fàbrega, honorary collaborator of the GUAIX group of the Complutense University of Madrid in Spain (currently at Lund University in Sweden), has found a way to correct these errors and carry out more accurate simulations.
In recent years, great progress has been made in computer simulations, allowing researchers to realistically calculate how galaxies form. These cosmological simulations are crucial to our theoretical understanding of the origin of galaxies, stars and planets. However, the predictions of these models are affected by limitations in numerical resolution and assumptions about a number of factors, such as star explosions, galactic flows, and stellar motions.
To minimize sources of error and produce more realistic simulations, 160 researchers from 60 universities have come together and formed the AGORA Collaboration, which now presents the results of its first set of cosmological simulations of the formation of a galaxy like ours, the Milky Way, in order to move towards a theory of galaxy formation, since it is crucial to compare the results and codes of different simulations. “Now we have achieved this by bringing together groups of codes that compete with each other, simulating galaxies, in a kind of supersimulator,” says Santi Roca-Fábrega.
Image of the formation of a galaxy the size of the Milky Way (in the center), in one of our AGORA simulations. You can see how gas is flowing from the cosmic web to fuel the formation of new stars in the galaxy. It is also seen that in the upper left another galaxy is approaching that will merge with the central one in the near future. The width of the image is one million light years (it would take a million years for light to traverse the entire image). (Image: AGORA CosmoRun)
The simulation is based on the same astrophysical assumptions about ultraviolet background radiation, gas cooling, heating, and star formation. With the help of the new results, researchers can determine that disk galaxies like the Milky Way could have started forming early in the history of the universe, completely consistent with observations from the James Webb telescope.
They have also discovered that the number of satellite galaxies (galaxies orbiting larger galaxies) is consistent with observations regardless of the simulation strategy used, which completely solves an old problem called the “missing satellite problem”, which consisted of the absence in observations of the large population of small satellite galaxies predicted by simulations of dark matter alone without the inclusion of gas and stars. Furthermore, the research team has revealed how recovering the observed properties of the gas surrounding galaxies is the key to obtaining realistic simulations, instead of adjusting the number and distribution of stars, which was usual until now.
Furthermore, as a result of these articles, new paths have been opened to better understand the formation of galaxies, in particular, the UCM doctoral student, Ramón Rodríguez Cardoso is analyzing how small galaxies are cannibalized by larger ones in a process which can last billions of years. The work has continued over the last eight years and has involved the execution of hundreds of simulations and the use of more than one hundred million hours in supercomputing facilities, explains Santi Roca-Fábrega.
Now work continues towards further refinement of simulations around galaxy formation. With each technological advance, Santi Roca-Fábrega and his colleagues hope to add new pieces to the puzzle of the dizzying question of the birth and evolution of the universe and galaxies.
“The collaboration has helped us improve the numerical codes by finding and correcting errors and better understanding how the parameters of each code control astrophysical processes, including star formation. This is the starting point for more reliable simulations of galaxy formation , which in turn will help us better understand our home galaxy, the Milky Way,” says Santi Roca-Fábrega. (Source: UCM)
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