Scientists Discover ‘Massive Gas Streams’ That Feed Galaxies

by Kareena Dodeja
Scientists Discover ‘Massive Gas Streams’ That Feed Galaxies

March 3, 2021

Scientists may have finally found evidence to a decade-old theory that massive galaxies in the universe were fed by cold gas streams that survived hotter surroundings. This, in fact, led to the formation of stars. This phenomenon was found in galaxy SMM J0913. Here's what you need to know about the findings.

What are these Gas Streams?

If we imagine the universe being just a few years old and think along the lines of time and space, this could give us a glimpse of an ancient era populated by many massive galaxies.

Some simulations suggest these galactic behemoths have been fed by cold gas in dark matter filaments, which are structures that make up the cosmic web. Large galaxies need cold gas streams to undergo a gravitational collapse. The larger a galaxy is, the more cold gas streams it needs to grow and expand. Scientists theorised the possibility two decades ago, and we finally might have evidence of this phenomenon.

Researchers led by the University of Iowa have detected cosmic pipelines supplying the cold gases necessary for the formation of massive galaxies and the creation of stars. It is the first direct observational evidence of the phenomenon in the early universe.

Hai Fu, and his group of scientists at the University of Iowa, have discovered what they claim is a ‘pipeline’ or a  gas stream filament that feeds an enormous galaxy SMM J0913. According to them, it was probably formed when the universe was 2.5 billion years old. They have found cold gas streams cutting through the atmosphere of a dark matter halo, thereby supplying the prerequisite for a galaxy to form stars.

According to the study published in the Astrophysical Journal, the discovery of gas streams wasn’t an easy one. It took years to confirm the long-standing models, which suggest that there is star-forming material delivered to huge galaxies through these cosmic gas streams. This evidence could open up a lot of avenues of research.

Fu told Vice that is the best evidence he has for the mysterious gas streams. His previous studies have detected the possibilities of the filaments, but nothing was certain to capture the detailed chemical information to support their origin. 

Galaxy SMM J0913 led to gas streams

The group of scientists, along with Fu, identified the chemical signatures of the gas stream in the galaxy they had studied about. They were grateful to identify it because of the rare and fortuitous alignment of the giant luminous body surrounding it. The galaxy is known as SMM J0913, which is a part of the larger cosmic field that already contains two radiant quasars. These quasars are the special galactic cores among the brightest phenomenon in the universe. 

An artist’s impression of a galaxy forming stars from the material blasted out from a central supermassive black hole.

Fu’s team understood that because of the two quasars being located behind SMM J0913 from our perspective of Earth, there are going to present brilliant objects that backlight the galaxy. It could give them details about the gas streams that nourishes this entity. This gas stream was found in the silhouette against two bright quasars, said Fu. He explained that the cold gas streams had survived despite the hotter surrounding and allowed these galaxies to form stars.

An essential part of their research was using the Atacama Large Millimeter/submillimeter Array (ALMA) that captured the spectral information. The ALMA is currently the largest radio telescope on Earth. The team did a phenomenal job with the help of ALMA to probe the abundance of chemicals in the filament using the telescope.

Finding these Gas Streams

The results were awry as they showed the lack of heavy elements such as aluminium, carbon, or iron in the stream. The environment inside galaxies like SMM J0913 is enriched with heavy elements that are spewed out into stars, so it is tricky to figure out that gas stream piped in was from outside the galaxy and most likely from a depleted environment.

There was tons of research for years by Fu and his colleagues- they skimmed over observations of 70,000 galaxies for over five years to track down the perfect system in SMM J0913.

What is interesting is how the cold gas gets pumped into galaxies without disrupting the hot atmosphere surrounding these entities? The narrow filaments can be explained through cosmic simulations though they are hard to detect, and Fu had researched vastly to understand it.

Fu added that he was grateful for the precious telescope to find this interesting discovery. It had taken him years to understand the system, and he was excited that the final piece of the jigsaw was placed using the data of the telescope. The ALMA had helped him confirm his hunch that SMM J0913 was the exact galaxy to probe.

Preparing for more research on Galaxies

This study is proven to be a breakthrough to understand how the massive galaxies were formed in the early universe, but it does not stop here. There is much more left to uncover, and his team looked at two points along the stream, which could lead to a follow-up. Fu is determined to see this to a physical extent in March using the Keck Observatory in Hawaii. He aims to find more cold gas streams around the massive galaxies, and he is effectively going to do this through existing telescopes.


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