The merging of galaxy clusters produces a cosmic shockwave or tsunami that can give birth to new stars in dead galaxies, said a new study.
A galaxy cluster or cluster of galaxies is a structure consisting of anywhere from hundreds to thousands of galaxies bound together by gravity. They were the largest known structures in the universe until the 1980s when superclusters were discovered.
Over billions of years, galaxy clusters merged with adjacent clusters, releasing massive amounts of energy as the clusters collided. The resulting shock wave travels through the cluster like a tsunami.
Until now, however, astronomers had no evidence the galaxies were affected by these collisions until they observed galaxy cluster CIZA J2242.8+5301, or the Sausage galaxy cluster located 2.3 billion light-years away in the direction of the constellation Lacerta, ignite a new wave of star formation after merging with another galaxy cluster.
"The comatose galaxies in the Sausage cluster are coming back to life, with stars forming at a tremendous rate. When we first saw this in the data, we simply couldn't believe what it was telling us", said Andra Stroe, one of the researchers.
The new study suggests the merger of galaxy clusters has a major impact on star formation. The shock waves from the collision triggered turbulence in the galactic gas that ignited an avalanche-like collapse and the formation of very dense, cold gas clouds that forms new stars.
"But star formation at this rate leads to a lot of massive, short-lived stars coming into being, which explode as supernovae a few million years later," said David Sobral of Leiden and the University of Lisbon.
"The explosions drive huge amounts of gas out of the galaxies, and with most of the rest consumed in star formation, the galaxies soon run out of fuel. If you wait long enough, the cluster mergers make the galaxies even more red and dead - they slip back into a coma and have little prospect of a second resurrection."
Every cluster of galaxies has experienced a series of mergers during its lifetime so they should all have gone through a period of very energetic star formation.