Light on dark

Astrophysicists are searching for enlightenment on some of the darkest mysteries of deep space

The existence of dark galaxies, giant clouds of hydrogen and dark matter that are the building blocks of stars, but fail to form stars, has long been the topic of scientific debate.  Now a UQ researcher has gone some way to disproving the dark galaxy theory.

Marianne Doyle, a PhD student with UQ’s Astrophysics Research Group and part of the international HI Parkes All Sky Survey (HIPASS) collaboration, has catalogued the whole of the southern sky and failed to find any evidence of dark galaxies.  “There should be loads of them but we didn’t find any,” she said.

In 1976, astrophysicist Mike Disney predicted there should be a large population of previously undetected very faint galaxies, some being dark galaxies that did not form stars.  All but one dark galaxy claim have so far been proven incorrect; a possible find in the Virgo cluster still a hot topic.

Ms Doyle spent two-and-a-half years searching radio data obtained by CSIRO’s Parkes radio telescope and cross-checking it with optical data from the Anglo-Australian Observatory’s UK Schmidt Telescope (AAT) at Siding Spring Observatory in New South Wales.  The radio data from the HIPASS catalogue revealed clouds of hydrogen in space, while the optical data from the SuperCOSMOS surveys and 6dF Galaxy Survey showed the positions of the galaxies that had formed stars.

“All the hydrogen clouds seem to be associated with galaxies that have stars,” Ms Doyle said.

Testing theories about another dark space issue will be easier for UQ astrophysics researchers who have received a 220-night allocation worth $4.4 million from the AAT to study dark energy.

The project will involve the largest-ever galaxy survey undertaken by telescope and will measure some 400,000 distant galaxies.

Project leader Associate Professor Michael Drinkwater said the technology at the AAT would put Australian research well ahead of international competition.

“Dark energy is a mysterious force which is causing the expansion of the Universe to accelerate. Its nature is completely unknown and it may require new laws of physics to be written,” Dr Drinkwater said.

Dr Drinkwater will work with fellow researchers Dr Kevin Pimbblet and Russell Jurek from UQ Physics.

Dr Pimbblet, an astrophysicist with UQ’s School of Physical Sciences, has also been investigating the edges of the Universe.  He has just finished a decade-long project cataloguing clusters of galaxies stretching to almost three billion light years away.  Dr Pimbblet was also looking at the biggest structures in the Universe.

“These are some of the largest structures you will find, with the distance from the core to the edge of the clusters reaching up to 10 megaparsecs, or 32.6 million light years,” he said.

Dr Pimbblet said apart from cataloguing galaxy clusters in the southern hemisphere for the first time, his work is also helping increase understanding of how the Universe evolved.

DARK GALAXY

DARK ENERGY GALAXY CLUSTERS

 

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