The cosmological simulation, dubbed "TNG-Cluster", has explored in unprecedented detail the realm of the largest gravitationally bound structures in the universe: gigantic collections of thousands of galaxies with a total mass of one million billion solar masses or more. The TNG-Cluster simulation enables new scientific studies and analyses as well as comparisons with real massive galaxy clusters. The simulation is a project by researchers from the Center for Astronomy at Heidelberg University (ZAH) and the Max Planck Institute for Astronomy (MPIA).
Compromise between size and richness of detail
In their project to simulate the formation of particularly massive galaxy clusters, the researchers had to find a compromise between the sufficient size of their model universe and the richness of detail with which they simulate the physical processes taking place.
For TNG-Cluster, the researchers developed a new method. They first simulated the formation of structures in a gigantic cube-shaped model universe with an edge length of more than 3 billion light-years. The cube was initially filled exclusively with Dark Matter, which accounts for about 80% of the total mass of matter in our real universe. Even though astronomers still don't know what dark matter is made of, they can measure its properties very accurately and find out that the way dark matter clumps together is almost completely independent of the presence of normal matter as we find it in interstellar gas or stars.
Zoom in on details
Taking this property into account and after letting their model universe evolve over the full age of the Universe, they identified several hundred regions where dark matter had accumulated and formed ultra-massive galaxy clusters. For each of these regions, the researchers ran a new simulation, but this time involving gas, stars, and supermassive black holes that form in the centers of galaxies.
"With this approach, we were able to generate a unique scientific dataset," says the project's co-PI, Dr. Dylan Nelson from the Institute for Theoretical Astrophysics (ITA), which is part of the Center for Astronomy at Heidelberg University (ZAH). "It allows us and researchers worldwide to not only study a large sample of galaxy clusters, but also to resolve small-scale details within each cluster. This includes not only the galaxies that make up the clusters, but also the processes in the gas of the hot intracluster medium," the astrophysicist enthusiastically remarks.
TNG-Cluster surpasses previous simulations of galaxy clusters. The data are so detailed that the researchers can even study the properties of the "intracluster medium", i.e. gas that nebulously surrounds galaxy clusters and emits intense X-rays, and including the different types of galaxies and the interactions they have experienced in the course of their formation.
Feedback from black holes
The research group that developed TNG-Cluster and now shares their simulation data publicly has already gained and published numerous findings. For instance, supermassive black holes become active when they swallow matter from their surroundings, forming "active galactic nuclei". The considerable amounts of energy they release into the surrounding space leave behind characteristic features, such as almost matter-free ‘cavities’ or shock fronts of compressed gas. These are visible to X-ray telescopes.
The processes in the vicinity of supermassive black holes take place on scales that are too small even for TNG-Cluster and have therefore only been modeled in a simplified way. The researchers were nevertheless impressed that their model reproduces many of the properties of such cavities quite realistically.
TNG-Cluster for everyone
Researchers involved in the previous TNG simulations, including Nelson and Pillepich, are committed to sharing not only their own results, but all information about their simulated model universe with the scientific community. In fact, of the more than 1000 publications based on TNG data so far, more than 700 have been written entirely by scientists who do not belong to the original team of 11 researchers of the TNG collaboration
Since March 5, 2025, scientists and the public are able to access the synthetic universe of the new TNG-Cluster simulation, including hundreds of terabytes of data via https://www.tng-project.org/data. The publication of the data is accompanied by a series of scientific publications, which add to a further dozen TNG-Cluster articles that the Heidelberg teams have already published (see https://www.tng-project.org/cluster/#results).
LOCAL CONTACTS
Contact for the Media
Dr. Guido Thimm
Center for Astronomy at Heidelberg University (ZAH)
thimm@uni-heidelberg.de
Scientific contact
Dr. Dylan Nelson
Center for Astronomy at Heidelberg University (ZAH)
Instituzte for Theoretical Astrophysics (ITA)
dnelson@uni-heidelberg.de
