University of Melbourne

Astrophysicists from the University of Melbourne and the Harvard-Smithsonian Center for Astrophysics have confirmed the theory that the formation of ‘dwarf’ galaxies was sabotaged a billion years after the Big Bang.

Their research, recently published in Nature, is the first observational evidence for the self-destructive behaviour of early galaxies. It supports the theory that larger instead of smaller ‘dwarf’ galaxies survived the initial period of galaxy formation after the Big Bang.

Dr Stuart Wyithe, of the University of Melbourne’s School of Physics, says the first galaxies were mini-furnaces forged into a multitude of hot, massive stars.

“According to theory, dwarf galaxies prevented subsequent generations from forming by heating surrounding hydrogen gas and bathing the universe in ultra violet radiation,” he says.

“Although this was theoretically known, it was not proven. We now have evidence that this occurred at the end of a period called the ‘Dark Ages’, when the unstructured elements in space evolved under gravity into the universe we see today.”

Dr Wyithe and his collaborator Professor Abraham Loeb (Harvard-Smithsonian Center for Astrophysics) were able to determine sizes of early galaxies by examining previous observations of powerful sources of light called quasars.

Quasar light is absorbed by intervening clouds of hydrogen in the early Universe. The presence of fewer, larger galaxies leads to more variation in the absorption seen across various lines of sight.

“We found that fluctuations in light from quasars implied that the early universe was sparsely populated,” says Dr Wyithe.

“Great advances have been made over the past decade in understanding how galaxies were formed, but there is still a lot to learn.”

According to Dr Wyithe astronomers will soon be able to use radio and infrared telescopes that can detect distant hydrogen and directly image young galaxies.

“Within the next decade researchers will be able to further illuminate the ‘Dark Ages’ of the universe,” he says.

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Editor's Note: Original news release can be found here.