New data from NASA's Jet Propulsion Laboratory has revealed that the relationship between galaxy clusters, which consist of thousands of galaxies, and elusive dark matter, is more complex than we originally thought. Although we know that galaxy clusters lay in regions where dark matter is denser than usual, a new study claims that the density of dark matter is linked to the internal structure of galaxy clusters.
"Galaxy clusters are like the large cities of our universe," Hironao Miyatake at NASA's Jet Propulsion Laboratory, said in a press release. "In the same way that you can look at the lights of a city at night from a plane and infer its size, these clusters give us a sense of the distribution of the dark matter that we can't see."
Now, for the first time, the new study suggests that the internal structures of galaxy clusters are linked to the dark matter environment in its proximity. The team came to the conslucion after studying approximately 9,000 galaxy clusters from the Sloan Digital Sky Survey DR8 galaxy catalogue. Using this data, they listed two groups of clusters - those with spread out galaxy distributions and those with tightly packed galaxy distributions.
When comparing these two groups, they found that galaxy clusters with tightly packed galaxies had fewer neighboring clusters in their surrounding environment compared to the sparser clusters, suggesting that the surrounding dark matter determines how dense each galaxy cluster is.
"This difference is a result of the different dark-matter environments in which the groups of clusters formed. Our results indicate that the connection between a galaxy cluster and surrounding dark matter is not characterized solely by cluster mass, but also its formation history," Miyatake said.
The results confirm the leading theory on the origins of our universe, which hypothesizes that the galaxy clusters that we see today are the result of changes in the early universe's matter density stemming from the cosmic inflation that occurred after the Big Bang.
"The connection between the internal structure of galaxy clusters and the distribution of surrounding dark matter is a consequence of the nature of the initial density fluctuations established before the universe was even one second old," Miyatake said.
The findings were published in the Jan. 25 issue of Physical Review Letters.
