Maps of the large-scale structure of galaxies (purple) and gas temperature distributions within the cluster (pink). Brighter pink indicates higher temperature. The filamentary structure is found outside the cluster in the top-left direction, in contact with the hotter gas realm. The other fields in which there are few galaxies (black) contact the cooler realm. The length of the white line corresponds to 10 million light-years.
Credit: RIKEN
SYDNEY: Astronomers have the first evidence that galaxy clusters interact with the large-scale structure of the universe.
At the largest possible scale, the universe resembles a kind of cosmic web with voids – huge bubble-like areas with no matter – and filaments.
Filaments connect regions called clusters, which in turn encompass groups of tens to hundreds of galaxies, as well as dark matter and the 'intracluster medium': a superheated gas of charged ions.
Now, Japanese and Taiwanese researchers have used a combination of data from space and ground-based telescopes to uncover new details on the growth of galaxy clusters and how they interact with the large-scale structure of the universe as published in the May issue of The Astrophysical Journal.
Cluster: Abell 1689
The Japanese Space Agency JAXA's Suzaku satellite telescope captured the detailed structure of a cluster called Abell 1689.
The researchers also used NASA's Hubble Space Telescope and the 8.2 m Subaru telescope in Hawaii to measure how dark matter in the cluster warps light emanating from galaxies behind the cluster.
"It was known that galaxy clusters grow through cluster-cluster mergers," said lead author of the research, Madoka Kawaharada, from RIKEN (The Institute of Physical and Chemical Research) in Saitama, Japan.
Galaxy clusters interact with filaments
But until now no cluster interaction with the large-scale structure had been found.
"This is the first evidence that galaxy clusters do interact with the large scale structure [of the universe] in their evolution history," Kawaharada told Cosmos.
The evidence comes in the form of X-ray observations of the outskirts of the intracluster medium, superheated plasma that exists in clusters in between galaxies.
Plasma at 60 million degrees Celsius
At the edge of the intracluster medium, the researchers found a 'hot spot': a region of plasma - or ionised gas - with a temperature of around 60,000,000°Celsius.
Stretching outwards from this hot spot like a spidery finger is a filamentary structure made up of many galaxies.
