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When did galaxies settle down? Two billion years earlier than we thought

Last Updated on Monday, 03 November 2014 15:38
Published on Thursday, 30 October 2014 11:45

Astronomers have long sought to understand exactly how the Universe evolved from its earliest history to the cosmos we see around us in the present day. In particular, the way that galaxies form and develop is still a matter for debate.

galaxyzoo COS 5227 smallA Hubble Space Telescope image of a spiral galaxy seen when the Universe was less than a third of its current age. It shows the same barred feature as much older, settled disk galaxies. Credit: NASA, ESA, J. Kartaltepe (NOAO), C. Lintott (Oxford), H. Ferguson (STScI), S. Faber (UCO). Click for a full size image.Now a group of researchers have used the collective efforts of the hundreds of thousands of people that volunteer for the Galaxy Zoo project to shed some light on this problem. They find that galaxies may have settled into their current form some two billion years earlier than previously thought. Dr Brooke Simmons of the University of Oxford and her collaborators describe the work in a paper published in the journal Monthly Notices of the Royal Astronomical Society.

The team set Galaxy Zoo volunteers the task of classifying the shapes of tens of thousands of galaxies observed by the Hubble Space Telescope. These objects are typically very distant, so we see them as they appeared more than 10 billion years ago, when the universe was about 3 billion years old, less than a quarter of its present age.

The newly classified galaxies are striking in that they look a lot like those in today’s universe, with disks, bars and spiral arms. But theorists predict that these should have taken another 2 billion years to begin to form, so things seem to have been settling down a lot earlier than expected.

Dr Simmons comments: "When we started looking for these galaxies, we didn't really know what we'd find. We had predictions from galaxy simulations that we shouldn't find any of the barred features that we see in nearby, evolved galaxies, because very young galaxies might be too agitated for them to form."

"But we now know that isn't the case. With the public helping us search through many thousands of images of distant galaxies, we discovered that some galaxies settle very early on in the Universe."

ngc1365 rot smallA European Southern Observatory image of the barred spiral galaxy NGC 1365, rotated to match the orientation of the first image. NGC 1365 is about 56 million light years away, so we see it as it appears 56 million years ago, or 10 billion years later than the galaxy in the HST image. Credit: ESO/IDA/Danish 1.5 m/ R. Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron. Click for a full size image 

Media contact

Dr Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7734 3307 / 4582
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Science contact

Dr Brooke Simmons
University of Oxford
Tel: +44 (0)1865 273637
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Further information

The new work appears in B. D. Simmon et al., "Galaxy Zoo: CANDELS Barred Disks and Bar Fractions", Monthly Notices of the Royal Astronomical Society, vol. 445, pp. 3466-3474, 2014, published by Oxford University Press. A preprint of the paper is available on the arXiv.


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