- Astrophysicists study 41 nearby galaxy clusters to reveal connections between hot gas, dark matter, and stars.
- The sum of stars and gas across the clusters is a fixed fraction of the dark matter mass.
According to the Standard Model of particle physics, ordinary matter is the strongly clustered materials of our Universe, while the nature of the dark matter remains elusive.
But how these two components are related to each other in terms of cosmic time and spatial scales? Finding an answer to this question can help scientists understand the formation of galaxies, the behavior of dark matter, and other new physics.
Astronomers have been studying galaxy clusters — the largest objects in our universe — for years. These clusters contain nearly 1,000 large galaxies comprising of hot gas, dark matter, and ‘ordinary matter’ such as cooler gas and stars.
Recently, a team of astrophysicists led by the University of Birmingham and the University of Michigan revealed connections between three major components of a galaxy cluster: hot gas, dark matter, and stars. They used data obtained from LoCuSS (short for Local Cluster Substructure Survey) to measure these connections.
Anti-Correlation of Hot and Cold Baryons
Researchers have been working on this project for 12 years, collecting data from various space-based and ground-based telescopes. They utilized advanced statistical models and algorithms to deduce that the sum of stars and gas across the clusters is a fixed fraction of the dark matter mass. This indicates that the amount of hot gas decreases [proportionally] as stars form.
In the Universe, a particular amount of matter collapses to form galaxy clusters. You can see these clusters as ‘closed containers’. Once these clusters are formed, the hot gas either remains as gas or forms stars, but the overall amount remains constant.
Image credit: N.R.Fuller/National Science Foundation
In this study, researchers analyzed 41 nearby galaxy clusters to determine the anti-correlated behavior between the mass in hot gas and the mass in stars. Together, these 2 measurements provide the most accurate mass of the total system.
‘The calculations are laying the foundation for precise science with galaxy clusters.’ – Alexis Finoguenov, a research team member.
The detection of anti-correlation indicates that large clusters of galaxies retain close to the mix of dark matter and baryons. This discovery can underpin enhanced cluster cosmology from cross-wavelength sample analysis.
The findings will help scientists study the characteristics of the universe as a whole and better understand the nature of dark matter and resolve the long-standing mystery of universe expansion.