Published on Friday, 24 April 2015
Galaxies are often found in clusters, with many 'red and dead' neighbours that stopped forming stars in the distant past. Now an international team of astronomers, led by Andra Stroe of Leiden Observatory and David Sobral of Leiden and the University of Lisbon, have discovered that these comatose galaxies can sometimes come back to life. If clusters of galaxies merge, a huge shock wave can drive the birth of a new generation of stars – the sleeping galaxies get a new lease of life. The scientists publish their work in the journal Monthly Notices of the Royal Astronomical Society.
A radio image highlighting the shock wave (seen here as the bright arc running from bottom left to top right) in the ‘Sausage’ merging cluster, made using the Giant Metrewave Radio Telescope. The shock wave was generated 1 billion years ago, when the two original clusters collided, and is moving at a very high speed of 9 million kilometres per hour. Credit: Andra Stroe.
Galaxy clusters are like cities, where thousands of galaxies can be packed together, at least in comparison to the sparsely-populated space around them. Over billions of years, they build up structure in the universe - merging with adjacent clusters, like growing cities absorb nearby towns. When this happens, there is a huge release of energy as the clusters collide. The resulting shock wave travels through the cluster like a tsunami, but until now there was no evidence that the galaxies themselves were affected very much.
Stroe and Sobral observed the merging galaxy cluster CIZA J2242.8+5301, nicknamed the 'Sausage', located 2.3 billion light years away in the direction of the constellation of Lacerta, in the northern hemisphere of the sky. They used the Isaac Newton and William Herschel Telescopes on La Palma, and the Subaru, CFHT and Keck Telescopes on Hawaii, and found that far from ‘watching from the back’ the cluster galaxies were transformed by the shock wave, triggering a new wave of star formation.
Stroe comments: "We assumed that the galaxies would be on the sidelines for this act, but it turns out they have a leading role. 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."
The rest of this article, with images, can be found at :
http://www.ras.org.uk/news-and-press/2619-giant-cosmic-tsunami-wakes-up-comatose-galaxies
Stroe and Sobral observed the merging galaxy cluster CIZA J2242.8+5301, nicknamed the 'Sausage', located 2.3 billion light years away in the direction of the constellation of Lacerta, in the northern hemisphere of the sky. They used the Isaac Newton and William Herschel Telescopes on La Palma, and the Subaru, CFHT and Keck Telescopes on Hawaii, and found that far from ‘watching from the back’ the cluster galaxies were transformed by the shock wave, triggering a new wave of star formation.
Stroe comments: "We assumed that the galaxies would be on the sidelines for this act, but it turns out they have a leading role. 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."
The rest of this article, with images, can be found at :
http://www.ras.org.uk/news-and-press/2619-giant-cosmic-tsunami-wakes-up-comatose-galaxies
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