Shadowy Galaxies' Size Revealed, 40 Year-Old Mystery Solved

First Posted: Jan 13, 2016 01:30 PM EST

Researchers have discovered ancient cold gas clouds that are more massive than some galaxies in the early universe. Some of the world's largest telescopes were used to carry out the study, which was presented at the 227th meeting of the American Astronomical Society in Florida. This new discovery has enabled the researchers to solve an old puzzle on the nature of gas clouds known as damped Lyman alpha systems, or DLAs. The finding of DLA gas clouds with background galaxies would enable researchers to measure their size, which would determine how much of the galaxy they occupy.

"Our new method first identifies galaxies that are more likely to have intervening DLA gas clouds and then searches for them using long, deep exposures on the powerful Keck Observatory 10m telescopes in Hawaii and deep data from the VLT 8m telescopes in Chile," Jeff Cooke, lead author of the study from Swinburne University of Technology, said in a news release.

DLA clouds are comprised of cool gas in the universe. Some scientists believe that these clouds contain sufficient gas that forms most of the stars that are seen in many surrounding galaxies, such as the Milky Way. However, this theory has not been confirmed.

DLAs are usually too dim to be observed and their emitted light is not bright enough. They are typically detected when they fall in sight of distant bright objects where they leave an unmistakable absorption signature in the background object's light. 

"Using the galaxy technique, DLAs can be studied in large numbers to provide a 3-D tomographic picture of distribution of gas clouds in the early Universe and help complete our understanding of how galaxies formed and evolved over cosmic time," said John O'Meara, coauthor of the study.

The findings of this study were published in The Astrophysical Journal Letters.

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