Regular spiral galaxies, such as the ‘whirlpool galaxy’ on the left, form far fewer stars than the clumpy galaxy on the right. The blue regions have the least star-forming gas and red-yellow regions have the most. Credit: Dr Danail Obreschkow, ICRAR. Image uses data from the Hubble Space Telescope.
Australian researchers have discovered why some galaxies are “clumpy” rather than spiral in shape – and it appears low spin is to blame. The finding challenges an earlier theory that high levels of gas cause clumpy galaxies and sheds light on the conditions that brought about the birth of most of the stars in the Universe.
Dr Danail Obreschkow from ICRAR, said 10B years ago the Universe was full of clumpy galaxies but these developed into more regular objects as they evolved. He said the majority of stars in the sky today, including our 5Byo Sun, were probably born inside these clumpy formations. “The clumpy galaxies produce stars at phenomenal rates,” Dr Obreschkow said. “A new star pops up about once a week, whereas spiral galaxies like our Milky Way only form about 1 new star a year.”
The research team focused on a few rare galaxies aka DYNAMO galaxies. They still look clumpy even though they’re seen “only” 500 million years in the past. Dr Obreschkow said looking at galaxies 500 million years ago was like looking at a passport photo taken a year ago. “The galaxies that are 10 billion light years away, that’s comparable to a picture from when you were three or four years old, that’s very different.”
The team used the Keck and Gemini observatories in Hawaii to measure the spin of the galaxies, along with millimetre and radio telescopes to measure the amount of gas they contained. DYNAMO galaxies had a low spin and this was the dominant cause of their clumpiness, rather than their high gas content as previously thought. “While the Milky Way appears to have a lot of spin, the galaxies we studied here have a low spin, about 3X lower,” he said.
Prof Glazebrook said the finding was exciting because the first observation that galaxies rotate was made exactly 100 years ago. “This novel .result suggests that spin is fundamental to explaining why early galaxies are gas-rich and lumpy while modern galaxies display beautiful symmetric patterns.”
http://www.icrar.org/news/news_items/media-releases/new-spin-on-star-forming-galaxies
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