Astronomers spun up by galaxy-shape finding

Giant elliptical galaxy M60 and smaller spiral galaxy, NGC 4647

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Using data provided by the Sydney-AAO Multi-object Integral field spectrograph (SAMI) at the 3.9m Anglo-Australian Telescope, Australian scientists have discovered have measured how a galaxy’s spin affects its shape.

For the first time astronomers have measured how a galaxy’s spin affects its shape.

It sounds simple, but measuring a galaxy’s true 3D shape is a tricky problem that astronomers first tried to solve 90 years ago.

“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, who completed this research while working at the Australian Astronomical Observatory.

The study was published on 11 September 2017 in the journal Monthly Notices of the Royal Astronomical Society.

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 disks of stars, the faster-spinning ones have more circular disks,” said team member Professor 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.

 

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.

The AAO is a division of the Department of Industry, Innovation and Science.

 

Publication details:

C. Foster and 19 coauthors, “The SAMI Galaxy Survey: the intrinsic shape of kinematically selected galaxies”. 2017, Monthly Notices of the Royal Astronomical Society (MNRAS), 472, 966. Online: https://doi.org/10.1093/mnras/stx1869

 

Further information:

Link to “SAMI Galaxy Survey” webpage: https://sami-survey.org/

Link to “Sydney-AAO Multi-object Integral-field” unit: https://www.aao.gov.au/science/instruments/current/sami

Further details about the “SAMI Galaxy Survey” can be found in our recent (26thJuly 2017) Media Release “Scientists unveil new 3D view of galaxies”: https://www.aao.gov.au/news-media/media-releases/scientists-unveil-new-3D-view-of-galaxies

 

Science Contacts:

- Dr Caroline Foster

The University of Sydney

P: +61 430 453 532 E: Caroline.Foster@sydney.edu.au

 

Media contact:

- Dr Ángel López-Sánchez

Research Astronomer and Science Communication Officer, Australian Astronomical Observatory

M: +61 406 265 917 E: angel.lopez-sanchez@aao.gov.au

 

- Helen Sim

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

M: +61 419 635 905 E: Helen.Sim@sydney.edu.au

 

Images:

The giant elliptical galaxy M60 and smaller spiral galaxy, NGC 4647 

Caption: 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.

This image is available at: https://www.aao.gov.au/files/press/arp-116-large.jpg

High-spin galaxies gif 

Animated gif: High-spin galaxies are like flat pancakes. They can appear to us at different angles. Credit: C. Foster (University of Sydney).

This animated gif is available at: https://www.aao.gov.au/files/press/HighSpinGalaxies_3D.gif

 

Video: Caroline Foster talks her work on measuring galaxy shapes, which she began while at the Australian Astronomical Observatory. Credit: Ángel R. López-Sánchez (Australian Astronomical Observatory/Macquarie University).

This video is available at: https://www.dropbox.com/s/p8uybdwwoaehm76/caroline-foster-HD-1080p-shorter-edited.mov?dl=0

 

Full Media Release in DOC format.