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Astronomers spun up by galaxy-shape finding

Last Updated on Friday, 08 September 2017 15:43
Published on Monday, 11 September 2017 15:00

It sounds simple, but measuring a galaxy’s true 3D shape is a tricky problem that astronomers first tried to solve 90 years ago. However, for the first time astronomers have measured how a galaxy’s spin affects its shape, in new research published in the journal Monthly Notices of the Royal Astronomical Society.

 

“This is the first time we’ve been able to reliably measure how a galaxy’s shape depends on any of its other properties – in this case, its rotation speed,” said research team leader Dr Caroline Foster of the University of Sydney.

thumb arp-116-largeThe giant elliptical galaxy M60 and smaller spiral galaxy, NGC 4647, located in the constellation Virgo. From our vantage point both galaxies look round but they have intrinsically different shapes. Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)–ESA/Hubble Collaboration. Click for a larger image

 

Galaxies can be shaped like a pancake, a sea urchin or a football, or anything in between. Faster-spinning galaxies are flatter than their slower-spinning siblings, the team found.

 

“And among spiral galaxies, which have discs of stars, the faster-spinning ones have more circular discs,” said team member Prof Scott Croom of the University of Sydney.

 

The team made its findings with SAMI (the Sydney-AAO Multi-object Integral field unit), an instrument jointly developed by The University of Sydney and the Australian Astronomical Observatory with funding from CAASTRO, the ARC Centre of Excellence for All-sky Astrophysics.

 

SAMI gives detailed information about the movement of gas and stars inside galaxies. It can examine 13 galaxies at a time and so collect data on huge numbers of them.

 

Dr Foster’s team used a sample of 845 galaxies, over three times more than the biggest previous study. This large number was the key to solving the shape problem.

 

Because a galaxy’s shape is the result of past events such as merging with other galaxies, knowing its shape also tells us about the galaxy’s history.

 


Media contacts

 

Ms Helen Sim

ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)

Mob: +61 419 635 905

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Dr Morgan Hollis

Royal Astronomical Society

Tel: +44 (0)2072 923 977

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Dr Alyssa Drake

Royal Astronomical Society

Tel: +44 (0)2072 923 976

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Science contacts

 

Dr Caroline Foster

The University of Sydney

Mob: +61 430 453 532

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Prof Scott Croom

The University of Sydney

Tel: +61 2 9036 5311

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Images and captions

 

The giant elliptical galaxy M60 and smaller spiral galaxy, NGC 4647, located in the constellation Virgo. From our vantage point both galaxies look round but they have intrinsically different shapes.

Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)–ESA/Hubble Collaboration.

 


Further information

 

The new work appears in: "The SAMI Galaxy Survey: the intrinsic shape of kinematically selected galaxies", C. Foster, J. Van de Sande, F. D'Eugenio, et al., Monthly Notices of the Royal Astronomical Society (2017) 472 (1) (DOI: 10.1093/mnras/stx1869).

A copy of the paper is available from: https://doi.org/10.1093/mnras/stx1869

 

The ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) is a collaboration between The University of Sydney, The Australian National University, The University of Melbourne, Swinburne University of Technology, The University of Queensland, The University of Western Australia and Curtin University, the last two participating together as the International Centre for Radio Astronomy Research (ICRAR). CAASTRO is funded under the Australian Research Council (ARC) Centre of Excellence program, with additional funding from the seven participating universities and from the NSW State Government's Science Leveraging Fund.

 


Notes for editors

 

The Royal Astronomical Society (RAS, www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

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