This time, using information on the structure of galaxy clusters, cosmologists have discovered fresh support for the mainstream model of cosmology.
In a recent study, a group of physicists from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory made careful measurements of the X-ray emission from galaxy clusters, which showed the distribution of stuff within them. The information also enabled researchers to evaluate the dominant hypothesis of the universe’s structure and evolution, called Lambda-CDM.
Getting there wasn’t an easy task, however.
Here’s the trouble: When the force of gravity, which keeps the entire system together, balances the energy in the gas within galaxy clusters, it is most trustworthy to infer the mass distributions of those structures from their X-ray emission.
As a result, measurements of the mass distributions in actual clusters concentrate on those that have attained a “relaxed” state of stability. It is crucial to consider this collection of loosened clusters when comparing results to theoretical predictions.
Keeping this in mind, Stanford physics graduate student Elise Darragh-Ford and her colleagues examined computer-simulated clusters produced by The Three Hundred Project.
The measured relationships agree extremely well between observation and theory, providing strong support for the Lambda-CDM paradigm.
Darragh-Ford
First, they computed what the X-ray emission for each simulated cluster should look like. Then, to narrow the set down, they applied the same observational criteria used to distinguish relaxed galaxy clusters from actual data to the simulated images.
The researchers next measured the relationships between three properties the cluster mass, how centrally concentrated this mass is, and the redshift of the clusters, which reflects how old the universe was when the light we observe was emitted, for both the simulated Three Hundred Project clusters and 44 real clusters observed with NASA’s Chandra X-ray Observatory.
Overall, clusters have been more centrally concentrated over time, and at any particular time, less big clusters are more centrally concentrated than more enormous ones, according to the team’s findings from both data sets.
“The measured relationships agree extremely well between observation and theory, providing strong support for the Lambda-CDM paradigm,” said Darragh-Ford.
The researchers anticipate being able to increase the amount of their analysis data sets for both the observed and simulated galaxy clusters in the future. SLAC-supported projects coming online in the next few years, including the Rubin Observatory’s Legacy Survey of Space and Time and the fourth-generation cosmic microwave background experiment (CMB-S4), will help identify a much larger number of galaxy clusters, while planned space missions, such as the European Space Agency’s ATHENA satellite, can follow up with X-ray measurements.
Additionally, SLAC cosmologists are trying to increase the scope and precision of computer models of the cosmos, enabling a more thorough investigation of galaxy clusters and the imposition of strict constraints on alternative cosmological hypotheses.
The National Aeronautics and Space Administration and the DOE Office of Science supported the research.
