Cosmologists have found new evidence for the Standard Model of Cosmology – this time using data on the structure of galaxy clusters. In a recently published study Monthly Notices of the Royal Astronomical SocietyA team led by physicists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University made detailed measurements of X-ray emission from galaxy clusters that reveal the distribution of matter. in them. In turn, the data helped scientists test the prevailing theory about the structure and evolution of the universe, known as Lambda-CDM.

However, getting there was no easy task.

Here’s the problem: Understanding the mass distribution of galaxy clusters in terms of X-ray emissions is most reliable when the energy of the gas in the clusters is balanced by the gravitational force that holds the entire system together. Therefore, measurements of mass distribution in real clusters focus on those that have fallen into a “relaxed” state. Therefore, it is important to take this loose set selection into account when comparing with theoretical predictions.

With this in mind, Elise Darragh-Ford, a graduate student in the Stanford Department of Physics, and her colleagues studied clusters created by computer simulations as part of the Three Hundred Project. First, they calculated what the X-ray emission should look like for each simulated cluster. They then applied the same observational criteria used to identify comfortable galaxy clusters from real data to the simulated images to eliminate the set.

The researchers then measured the relationship between three properties: the cluster mass, how dense that mass is at the center, and the cluster redshift, which reflects how old the universe was when the light we observed was emitted, measured for both simulated projects, the Three Hundreds. . Clusters and 44 real clusters observed with NASA’s Chandra X-ray Observatory.

The team found consistent results from both datasets: overall, clusters were more centrally concentrated over time, while at any given time, less large clusters were more centrally concentrated than larger ones. “The measured relationships fit very well between observation and theory and provide strong support for the Lambda-MCP paradigm,” said Darragh-Ford.

In the future, scientists hope to expand the size of both observed and simulated galaxy cluster datasets in their analysis. SLAC-supported projects, which will be made available online over the next few years, including the Space-Time Survey at Rubin Observatory and the Cosmic Microwave Background Fourth Generation (CMB-S4) experiment, will help identify many more galaxy clusters than anticipated. Space missions, such as the European Space Agency’s ATHENA satellite, can perform X-ray measurements. SLAC cosmologists are also working to expand the size and accuracy of computer simulations of the cosmos by making it possible to study galaxy clusters more thoroughly and to place tighter constraints on alternative cosmological scenarios.