15 Sep 2016
UWA, Australia, uses Integral Field Spectroscopy to quantify how gas and stars move, "reinterpreting Hubble sequence".
Dr Luca Cortese, from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), said the world’s premier astronomical facilities are now producing surveys consisting of hundreds of thousands of galaxies rather than the dozens that Hubble and his contemporaries were working with. We need a way to classify galaxies consistently using instruments that measure physical properties rather than a time consuming and subjective technique involving human interpretation.”
“Thanks to the development of new technologies, we can map in great detail the distribution and velocity of different components of galaxies. Then, using this information we’re able to determine the overall angular momentum of a galaxy, which is the key physical quantity affecting how the galaxy will evolve over billions of years.
“Remarkably, the galaxy types described by the Hubble scheme appear to be determined by two primary properties of galaxies–mass and angular momentum. This provides us with a physical interpretation for the well known Hubble sequence whilst removing the subjectiveness and bias of a visual classification based on human perception rather than actual measurement.”
The SAMI project, led by the University of Sydney and the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), aims to create one of the first large-scale resolved survey of galaxies, measuring the velocity and distribution of gas and stars of different ages in thousands of systems.
“Australia has a lot of expertise with this type of astronomy and is really at the forefront of what’s being done,” said Professor Warrick Couch, Director of the Australian Astronomical Observatory and CAASTRO Partner Investigator.“For the SAMI instrument we succeeded in putting 61 optical fibres within a distance that’s less than half the width of a human hair.
Observing galaxy transitions
Future upgrades of the instrument are planned that will allow astronomers to obtain even sharper maps of galaxies and further their understanding of the physical processes shaping the Hubble sequence.
“As we get better at doing this and the instruments we’re using are upgraded, we should be able to look for the physical triggers that cause one type of galaxy to evolve into another—that’s really exciting stuff,” Dr Cortese said.
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