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Atlas reveals a visual feast of galaxies

Galaxy pair NGC 4676

The duo of galaxies known as NGC 4676—also known as the Mice Galaxies because of their "tails"—have come so close to each other that they're in the process of merging.

A NEW BOOK about galaxies has been released by astronomer Dr Glen Mackie from Swinburne University in Melbourne, Australia.

The Multiwavelength Atlas of Galaxies contains more than 250 colour images contributed by Mackie and more than 100 astronomy colleagues.

“The atlas shows the huge variety of galactic structures when observing the entire electromagnetic spectrum, not just the optical region,” Mackie said.

“Historically we’ve tended to look at galaxies mainly at optical wavelengths, but that is really only about 10 per cent of the full story. Looking across the full spectrum you see what’s going on not only with stars, but with gas, dust, even electrons.”

Cover of Multiwavelength Atlas of Galaxies

Cover of the new book, Multiwavelength Atlas of Galaxies by Dr Glen Mackie.

The atlas explains why we see the component stars, gas and dust through different radiation processes.

The telescopes, instruments and detectors used to collect the images include the Hubble Space Telescope, the Chandra X-ray Observatory, the Spitzer Space Telescope and the Parkes 64m dish.

The atlas includes appendices describing the instruments used, image sources and technical descriptions, a cross-reference list of galaxies, and plots of spectral energy distributions.

Mackie began compiling the atlas images when he was a research astronomer at Harvard-Smithsonian Centre for Astrophysics in the late 1990s.

He envisaged the atlas as a textbook for astronomy students and a reference for professional astronomers, but it is also suitable for astronomy enthusiasts interested in learning more about the processes that have shaped and structured our universe.

The Multiwavelength Atlas of Galaxies can be purchased at the Cambridge University Press website http://www.cambridge.org/catalogue/catalogue.asp?isbn=9780521620628

Adapted from information issued by Swinburne University.

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Aussie student finds ‘living dinosaurs’ in space

Galaxies

Australian astronomers have found "living dinosaur" galaxies in the nearby universe. These types of galaxies had been thought to exist only earlier in the universe.

Using Australian telescopes, Swinburne University astronomy student Andy Green has found ‘living dinosaurs’ in space: galaxies in today’s Universe that were thought to have existed only in the distant past.

The report of his finding—Green’s first scientific paper—appears on the cover of the 7 October issue of the scientific journal, Nature.

“We didn’t think these galaxies existed. We’ve found they do, but they are extremely rare,” said Professor Karl Glazebrook, Green’s thesis supervisor and team leader.

The Swinburne researchers have likened the galaxies to the ‘living dinosaurs’ or Wollemi Pines of space—galaxies you just wouldn’t expect to find in today’s world.

“Their existence has changed our ideas about how star formation is fuelled and understanding star formation is important. Just look at the Big Bang, which is how we all got here,” Glazebrook said.

The galaxies in question look like discs, reminiscent of our own galaxy, but unlike the Milky Way they are physically turbulent and are forming many young stars.

“Such galaxies were thought to exist only in the distant past, ten billion years ago, when the Universe was less than half its present age,” Glazebrook said. “Stars form from gas, and astronomers had proposed that the extremely fast star formation in those ancient galaxies was fuelled by a special mechanism that could exist only in the early Universe—cold streams of gas continually falling in.”

Simulation of a star-forming galaxy

A simulation of a star-forming galaxy. Cold gas (red) flows into a spiral galaxy, feeding the process that forms stars.

But finding the same kind of galaxy in today’s Universe means that that mechanism can’t be the only way such rapid star formation is fuelled.

Instead it seems that when young stars form, they create turbulence in their surrounding gas. The more stars are forming in a galaxy, the more turbulence it has. “Turbulence affects how fast stars form, so we’re seeing stars regulating their own formation,” Green said.

“We still don’t know where the gas to make these stars comes from though,” he said. Understanding star formation is one of the most basic, unsolved problems of astronomy.

Another significant aspect of the paper is that it was authored by a PhD student. As Glazebrook pointed out, being first author of a Nature paper as a student is as rare as the galaxies they’ve discovered. This is an achievement not lost on the young scientist. “Nature is one of the most prestigious journals in science. It was a pleasant surprise for our work to receive this kind of accolade,” Green said.

Anglo-Australian Telescope

The 3.9-metre Anglo-Australian Telescope was one of the telescopes used in the study.

Australian observatories

The study was based on selected galaxies from the Sloan Digital Sky Survey, a kind of census of modern galaxies. “We studied extreme galaxies to compare them with the ancient Universe,” Green said. He observed them using the Anglo-Australian Telescope (AAT) and the Australian National University’s 2.3-metre telescope, both located at Siding Spring Observatory in New South Wales.

Professor Matthew Colless, Director of the Australian Astronomical Observatory, which operates the AAT, said that the study highlighted the value of the instruments found at Australia’s telescopes. “They are ideal for studying in detail the nearby counterparts of galaxies seen in the distant Universe by the eight and 10 metre telescopes,” he said.

For the next stage of his research, Green plans to use one of these 10 metre telescopes—in fact the largest optical telescope in the world at the Keck Observatory—to take an even closer look at the rare galaxies he has discovered. Green admitted: “Really, we need a bigger telescope, the Giant Magellan Telescope, to understand star formation. But, until it’s constructed, Keck is the best tool available.”

Green’s access to the Keck will be possible thanks to Swinburne’s agreement with Caltech, which gives the Swinburne astronomers access to the Keck Observatory in Hawaii for up to 20 nights per year.

Adapted from information issued by Swinburne University / Rob Crain / James Geach / Virgo Consortium / Andy Green / Swinburne Astronomy Productions. AAT photo by Barnaby Norris.

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