An international team of astronomers from Japan, Mexico and the University of Massachusetts Amherst (USA) has studied a “monstrous galaxy” 12.4 billion light years away, achieving an angular resolution 10 times greater than ever, which has made possible the discovery of previously completely unknown structural details of the galaxy. And they are as magnificent as you would expect.
Using the ALMA telescope in Atacama, Chile, scientists have also identified properties of this monstrous galaxy, called COSMOS-AzTEC-1, that had not previously been proven.
He was born only 1 billion years after the Big Bang
Astronomers found that molecular clouds in the galaxy are highly unstable, leading to the formation of runaway stars. These monstrous galaxies are believed to be the ancestors of the huge elliptical galaxies in the universe today, such as our Milky Way, giving us even more information to understand the formation and evolution of such galaxies.
“One of the best parts of ALMA observations is seeing distant galaxies with unprecedented resolution,” says Ken-ichi Tadaki, study leader in the journal Nature .
This type of monstrous galaxy forms stars at an astonishing rate – 1000 times faster than star formation in our galaxy. But why are they so active? To answer this question, you have to look at the environment of the stellar nurseries. Therefore, they focused on COSMOS-AzTEC-1. This galaxy was first discovered with the James Clerk Maxwell Telescope in Hawaii.
Among other things, this galaxy is rich in star ingredients, but it was still difficult to determine the nature of the cosmic gas in the galaxy. The team used the high resolution and high sensitivity of ALMA to observe this monstrous galaxy and obtain a detailed map of the distribution and movement of the gas. As a result, they have obtained the highest resolution molecular gas map of a distant monstrous galaxy to date.
“We discovered that there are two large clouds, distinct several thousand light years from the center,” explains Tadaki. “In most distant galaxies, stars are actively forming in the center. So it is surprising to find off-center clouds.”
Astronomers further investigated the nature of the gas in this galaxy and found that the clouds throughout the galaxy are very unstable, something that is truly unusual.
In a normal situation, inward gravity and outward pressure balance in clouds. Once gravity overcomes the pressure, the gas cloud collapses and forms stars at a rapid rate. So stars and supernova explosions at the end of the stellar life cycle expel gases, which increase the pressure outwards. As a result, gravity and pressure reach a balanced state and star formation continues at a moderate rate.
But e n COSMOS-AzTEC-1, the pressure is much weaker than gravity and difficult to balance. Therefore, this galaxy shows a star formation out of control and has been transformed into an unstoppable monstrous galaxy.
The researchers estimated that the gas will be completely consumed in 100 million years, which is 10 times faster than in other star-forming galaxies.
Why is your gas so unstable?
Astronomers don’t have a definitive answer yet, but galaxy merging is one possible cause.
“At this time, we have no evidence of fusion in this galaxy . By looking at other similar galaxies with ALMA, we want to reveal the relationship between galaxy mergers and monster galaxies,” concludes Tadaki.
Reference: A gravitationally unstable gas disk of a starburst galaxy 12 billion years ago, Nature (2018). DOI: 10.1038 / s41586-018-0443-1, https://www.nature.com/articles/s41586-018-0443-1
Image credit: National Astronomical Observatory of Japan
