London, Jan 11 : Astronomers are using NASA's Hubble Space Telescope to understand the violent lives of galaxies, a reason for which is irregular clumps of dark matter present in some galaxy superclusters.
The Hubble study pinpointed four main areas in the supercluster where dark matter has pooled into dense clumps, totalling 100 trillion times the Sun's mass. These areas match the location of hundreds of old galaxies that have experienced a violent history while moving from the outskirts of the supercluster into these dense regions.
"Thanks to Hubble's Advanced Camera for Surveys, we are detecting for the first time the irregular clumps of dark matter in this supercluster," said Dr Catherine Heymans of the University of British Columbia in Vancouver, Canada.
"We can even see an extension of the dark matter toward a very hot group of galaxies that are emitting X-rays as they fall into the densest cluster core," she added.
The survey's broader goal is to understand how galaxies are influenced by the environment in which they live, one aspect of which is the violent lives that they go through.
According to Dr Gray, galaxies are subject to a life of violence because they are continually drawn into larger and larger groups and clusters by the inevitable force of gravity as the universe evolves.
This violent life involves high-speed collisions with other galaxies, the stripping away of fuel supply they use to form new stars; and distortion due to the strong gravitational pull of the underlying invisible dark matter.
"Any or all of these effects may play a role in the transformation of galaxies, which is what we're trying to determine," Dr Gray said.
According to Christian Wolf, an Advanced Research Fellow at the University of Oxford, the transformations are happening in the outskirts of the supercluster, where galaxies are still moving relatively slowly and first feel the influence of the cluster environment.
"We see more collisions between galaxies in the regions toward which the galaxies are flowing than in the centres of the clusters," said Shardha Jogee, Assistant professor in the University of Texas in Austin, US. By the time they reach the centre, they are moving too fast to collide and merge, but in the outskirts their pace is more leisurely, and they still have time to interact," she added.
The research team now plans more studies to understand how the supercluster environment is responsible for producing all these changes in the galaxies.