Astronomers discover new details of 'monster' star-forming galaxies

A new study sheds light on the structure of the "monster galaxy" COSMOS-AzTEC-1.
By Tyler MacDonald | Aug 31, 2018
An international team of researchers examining a "monster galaxy" located 12.4 billion light years away from the Earth revealed that they achieved a milestone: an angular resolution 10 times higher than ever before, revealing previously unknown structural details.

"Monster galaxies," also known as extreme starburst galaxies, are believed to be the ancestors of giant galaxies like the current universe's Milky Way. And the more we know about them, the more we will discover more about the formation and evolution of our galaxy's ancient past.

"A real surprise is that this galaxy seen almost 13 billion years ago has a massive, ordered gas disk that is in regular rotation instead of what we had expected, which would have been some kind of a disordered train wreck that most theoretical studies had predicted," said study co-author Min Yun.

Yun added that they did observe that the galaxy's gas disk is now dynamically unstable, meaning that the entire disk that makes up the galaxy is undergoing an episode of starburst. This explains its large star formation rate, which is upwards of 1,000 times that of the Milky Way.

Ken-ichi Tadaki, lead author of the study, says that COSMOS-AzTEC-1 is rich in star ingredients. However, it was still difficult to determine the cosmic gas in the galaxy, even using the ALMA's high sensitivity and high resolution.

"We found that there are two distinct large clouds several thousand light-years away from the center," he said. "In most distant starburst galaxies, stars are actively formed in the center. So it is surprising to find off-center clouds."

"How these galaxies have been able to amass such a large quantity of gas in the first place and then essentially turn the entire gas reserve into stars in the blink of an eye, cosmologically speaking, was a completely unknown question about which we could only speculate,"Yun added. "We have the first answers now."

The findings were published in Nature.

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