July 10, 2014
Distant Galaxy Shows Evidence Of A ‘Red And Dead’ Future
John P. Millis, Ph.D. for redOrbit.com - Your Universe Online
When galaxies first form they are dominated by gas that, over time, lays the foundation for stars. As more stars form the gas becomes locked up in stellar objects and their core remnants, such as white dwarfs, neutron stars, and black holes. Eventually, the gas will become depleted, leaving behind a cold dead galaxy.
This process, however, can look different for varying galaxy types, and astronomers have been looking to identify markers to chart the evolution of these galaxies. One indicator is the existence of carbon monoxide in the galaxy, but it is in rare supply among galaxies at the outer reaches of the cosmos. That is why the recent discovery of this molecule in the galaxy ALESS65, some 12 billion light-years from Earth, is so important.
"We're familiar with carbon monoxide here on Earth as the deadly gas that can cause suffocation, but in galaxies it plays an important role in the lifecycle of stars," says Minh Huynh, an astronomer from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR). "Out of the galaxies that we know contain carbon monoxide, less than 20 are as far away from Earth as ALESS65. Out of the billions of galaxies out there, the detections are very rare!"
While the galaxy was first imaged in 2011 by the Atacama Large Millimeter Array (ALMA), only now have astronomers been able to determine the concentration of carbon monoxide it contains. Using the Australia Telescope Compact Array (ATCA), Huynh and her team were able to obtain the levels of the molecule that are visible, and extrapolate out how much gas the galaxy as a whole contains.
This is important because the carbon monoxide can be used to indicate how much fuel is left for star formation. From this, astronomers can construct how the galaxy will evolve in the future, in this case leading to a “red and dead” future.
"All galaxies have a certain amount of fuel to make new stars. Our galaxy, the Milky Way, has about five billion years before it runs out of fuel and becomes 'red and dead', but ALESS65 is a gas-guzzler and only has 10s of millions of years left – very fast in astronomical terms. We were able to work out the strength of the UV radiation in ALESS65; it's similar to some 'starbursting' galaxies in the local universe, but the stars in ALESS65 are forming in much larger areas when compared to local galaxies," said Huynh.
The next task for Huynh and her team will be to conduct a similar study with a galaxy near ALESS65, called ALESS61.
"Finding and studying carbon monoxide in more galaxies will tell us even more about how stars formed in the early days of the Universe and help solve the mystery of far away 'red and dead' galaxies," said Huynh.
A paper on the study is published in the Monthly Notices Of The Royal Astronomical Society.
Image 2 (below): Radio waves emitted from ALESS65 as observed by the Australia Telescope Compact Array. Credit: Huynh et al.
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