"Future Fellow" to sleuth galaxies' pasts

One of the Australian Research Council’s “Future Fellows” announced this week will join the Anglo-Australian Observatory in Sydney to investigate the youthful habits and associates of galaxies that are now old and staid.
Dr Chris Lidman is an Australian astronomer currently working with some of the world’s largest telescopes at the European Southern Observatory in Chile.
He is one of 200 recipients of the inaugural round of ARC Future Fellowships, awards of up to $135,000 a year for four years, plus $50,000 a year for infrastructure support, aimed at providing opportunities for mid-career researchers to work in Australia.
Dr Lidman’s project focuses on “early-type” galaxies, giant round or football-shaped masses of old stars.
“These galaxies have reached old age,” said Associate Professor Andrew Hopkins, Head of AAT Science at the Anglo-Australian Observatory. “They’re long past the time when they were actively forming stars.”
Nothing exciting has happened to these galaxies for a very long time.
“When we look back to when the Universe was only a third of the age it is now, the stars in these galaxies look a bit younger, but that’s it,” Prof. Hopkins said. “The real star-forming action must have happened earlier.”
They may be in rocking chairs now, but in their youth many of these galaxies were the hell-raisers of the cosmos, harbouring massive black holes that snorted jets of particles millions of light years into space.
Astronomers suspect that these galaxies formed their stars when the Universe was between a quarter and a third of its present age [1.4 < z < 2].
They also know that the company a galaxy keeps affects how it forms stars.
Galaxies hang out in gangs, or what astronomers more politely call “clusters”.
Cluster galaxies hassle each other with their gravitational forces, sometimes provoking their fellows to form stars.
Dr Lidman will be looking to detect the clusters housing early-type galaxies at the time when those galaxies were forming their stars.
The usual way to find clusters is to hunt for the X-ray emission from super-hot gas lying in the space between the cluster galaxies.
But this method reaches its limit when looking back to the time when the Universe was only a third of its present age [a redshift of 1.4].
Dr Lidman is going to use a new technique for detecting these distant clusters: taking infrared images with NASA’s Spitzer Space Telescope.
Spitzer’s IRAC camera is so sensitive it can spot massive galaxies that existed when the Universe was only three billion years old — a fifth of its present age.
Dr Lidman and his team will use ground-based telescopes, such as the Gemini South Telescope in Chile, and the Anglo-Australian Telescope in New South Wales, to measure the distances to the galaxies detected by Spitzer, and thus determine whether they lie in clusters or accidentally appear together on the sky.
“Finding the clusters is the first step towards understanding how these galaxies evolved in this early period of their lives,” Prof. Hopkins said.
The formal title of Dr Lidman’s project is Venturing into the Cluster Desert.
Three other Future Fellowships in astronomy were awarded, going to:
• Dr Duncan Galloway (for High-energy probes of dense matter and distorted spacetime, at Monash University);
• Dr Holger Baumgardt (for Advanced computer simulations of star cluster evolution, at the University of Queensland); and
• Dr Kenji Bekki (for Simulating the Magellanic system using new special-purpose computers for gravitational dynamics, at the University of Western Australia).

Researcher contacts

Associate Professor Andrew Hopkins
Head of AAT Science, Anglo-Australian Observatory, Sydney, Australia
Office tel: +61 2 9372 4849

Dr Chris Lidman
European Southern Observatory, Santiago, Chile
Office tel: +56 2 463 3107



One of the nearest galaxy clusters, the Virgo cluster. Photo by David Malin. Copyright Anglo-Australian Observatory / Royal Observatory Edinburgh.

Small jpeg - 1.1 MB

Large jpeg - 14.4 MB


Media assistance: Helen Sim 
+61-(0)2-9372-4251 (office)
+61-(0)419-635-905 (mob.)