Why massive galaxies don't dance in crowds

August 10, 2017, University of New South Wales
Why massive galaxies don’t dance in crowds
Galaxy cluster Abell 2744, imaged with the Hubble Space Telescope. The cluster lies in the constellation of Sculptor and contains several hundred galaxies. Credit: NASA, ESA, and R. Dupke (Eureka Scientific, Inc.), et al.

Scientists have discovered why heavyweight galaxies living in a dense crowd of galaxies tend to spin more slowly than their lighter neighbours.

"Contrary to earlier thinking, the spin rate of the galaxy is determined by its mass, rather than how crowded its neighbourhood is," says study first author Associate Professor Sarah Brough of UNSW Sydney and the ARC Centre of Excellence for All-sky Astrophysics, CAASTRO.

The finding, based on a detailed study of more than 300 , is published in the Astrophysical Journal.

To measure how fast their galaxies rotated, the researchers used an instrument called the Sydney-AAO Multi-object Integral field spectrograph (SAMI) on the 4-metre Anglo-Australian Telescope in eastern Australia.

SAMI 'dissects' galaxies, obtaining optical spectra from 61 points across the face of each galaxy, 13 galaxies at a time.

"We want to know which factors really drive how galaxies evolve," says team member Dr Matt Owers of the Australian Astronomical Observatory and Macquarie University. "In this case, we've sorted out nature versus nurture."

The new finding runs counter to previous studies, made with smaller samples of galaxies, which concluded that a galaxy's spin rate is determined by the other galaxies in its neighbourhood.

Associate Professor Brough says this earlier conclusion was spurious. "Once you take into account the strong association with mass, there's no link between a galaxy's spin rate and its environment," she says.

Credit: University of New South Wales

Explore further: Scientists unveil new 3-D view of galaxies

More information: Sarah Brough et al. The SAMI Galaxy Survey: Mass as the Driver of the Kinematic Morphology–Density Relation in Clusters, The Astrophysical Journal (2017). DOI: 10.3847/1538-4357/aa7a11

Related Stories

Scientists unveil new 3-D view of galaxies

July 28, 2017

For many years astronomers have struggled to get good-quality 3-D data of galaxies. Although this technique is very powerful as it allows researchers to "dissect" objects, this was a slow process as each galaxy had to be ...

The shapes of galaxies

June 26, 2017

Since Edwin Hubble proposed his galaxy classification scheme in 1926, numerous studies have investigated the physical mechanisms responsible for the shapes of spiral and elliptical galaxies. Because the processes are complex, ...

A new spin on star-forming galaxies

December 14, 2015

Australian researchers have discovered why some galaxies are "clumpy" rather than spiral in shape—and it appears low spin is to blame.

Recommended for you

Two sub-Jovian exoplanets orbiting bright stars discovered

March 19, 2018

Using NASA's prolonged Kepler mission, known as K2, astronomers have identified two new gas giant exoplanets. The newly found alien worlds, designated HD 89345 b and HD 286123 b, are warm, low-density sub-Jovian planets circling ...

Measuring white dwarf masses with gravitational lensing

March 19, 2018

Measuring the mass of a celestial body is one of the most challenging tasks in observational astronomy. The most successful method uses binary systems because the orbital parameters of the system depend on the two masses. ...

NASA powers on new instrument staring at the Sun

March 16, 2018

NASA has powered on its latest space payload to continue long-term measurements of the Sun's incoming energy. Total and Spectral solar Irradiance Sensor (TSIS-1), installed on the International Space Station, became fully ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (3) Aug 11, 2017
I think the most important phrase in the whole story is the words: "Contrary to earlier thinking"

That is the most important type of observation scientists can make as it overturns false data and false thinking which permeates and pervades our scientific data and discourse.
Captain Stumpy
not rated yet Aug 11, 2017
That is the most important type of observation scientists can make as it overturns false data and false thinking which permeates and pervades our scientific data and discourse
1- all science is on the frontiers of knowledge (important to remember)

2- colourful adjectives are not representative of all science, only reporting (and not always accurate)

3- you have absolutely no evidence that science, it's data or discourse, is permeated with false data or false thinking
this is important to note because it is demonstrative of your lack of science literacy on many levels: just because a point changes a hypothesis or adjusts data to make something more accurate doesn't mean it falsifies previous points or data

example: GR/SR
it also was "Contrary to earlier thinking", however we still use Newtonian physics

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.