Galaxies grow bigger and puffier as they age24 April 2018

An international study including researchers from the Australian Research Council (ARC) Centre of Excellence in All-Sky Astrophysics in 3D (ASTRO 3D) and the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) based at The Australian National University (ANU) and The University of Sydney, has found galaxies grow bigger and puffier as they age.

Co-researcher Professor Matthew Colless from ANU said that stars in a young galaxy moved in an orderly way around the galaxy’s disk, much like cars around a racetrack.

“All galaxies look like squashed spheres, but as they grow older they become puffier with stars going around in all directions,” said Professor Colless, who is an ARC Super Science Fellowship recipient and a Chief Investigator at ASTRO 3D.

The researchers studied 843 galaxies of all kinds and with a hundred-fold range in mass, measuring each galaxy's age by looking at the colour of its stars.

To work out a galaxy’s shape, the research team measured the movement of stars with an instrument called SAMI which was funded through the ARC's Linkage Infrastructure, Equipment and Facilities (LIEF) scheme, and which is attached to the Anglo-Australian Telescope at the ANU Siding Spring Observatory.

University of Sydney co-author Dr Julia Bryant, lead scientist for the SAMI instrument, said the team was still searching for the simple, powerful relationships like shape and age that underlie a lot of the complexity scientists see in galaxies.

“To see those relationships, you need detailed information on large numbers of galaxies,” she said. 

The Anglo-Australian Observatory (AAO) is building SAMI’s successor instrument, Hector, which is designed to observe 100 galaxies at a time, and which is also funded by the ARC's LIEF scheme.

The findings have been published in the journal Nature Astronomy.

Media issued by The Centre of Excellence in All-Sky Astrophysics in 3D.


Image: new research shows that galaxies like the spiral galaxy m83 (shown), grow bigger and puffier as they age.
Credit: NASA (Public Domain)

Original Published Date: 
Tuesday, April 24, 2018