Study Shows Cold Gas Pipelines Fed Early Massive Galaxies

Large galaxies in the early universe required a lot of cold molecular gases in order to coalesce and grow.
Fabienne Lang
Galaxy illustrationArtEvent ET/iStock

A new study shows evidence that cold gas streams fed the early, and massive galaxies. These large galaxies found in the early universe required a lot of cold molecular gases in order to coalesce and grow. 

The study was led by astronomers at the University of Iowa in the U.S., who reported observational evidence of these pipelines of cold gas that they believe are what provisioned these early and huge galaxies. 

After years in the making, the study was published in the Astrophysical Journal on Feb. 24.

Why galaxies need cold gas 'pipelines'

As the study's researchers explain, in order to come into being, galaxies need cold gas so as to undergo gravitational collapse. The bigger the galaxy, the more cold gas it needs to coalesce and grow.

The major question to answer was: How did these early supersized galaxies get this amount of cold gas when they were surrounded by such hot environments? 

Enter, the cold gas pipelines that streamed through this hot atmosphere.

In their study, the scientists focused on a gaseous region surrounding a massive galaxy formed when the universe was approximately 2.5 billion years old. As this galaxy hadn't yet been studied, it took the team five years just to pinpoint its location and distance. It managed to do so with the assistance of the Atacama Large Millimeter/Submillimeter Array.

Hai Fu, lead author of the study and associate professor at Iowa's Department of Physics and Astronomy, and his colleagues were able to identify the chemical signatures of the cold gas stream thanks to a well-timed alignment of quasars behind the galaxy — quasars are among some of the brightest objects in the universe.

Study Shows Cold Gas Pipelines Fed Early Massive Galaxies
Detection of the cosmic cold gas pipelines was possible thanks to two bright quasars. Source: Hai Fu/University of Iowa

The galaxy in question, named SMM J0913, is part of a bigger cosmic environment that includes two quasars. As these two bright objects are behind SMM J0913 (from our perspective on Earth) they backlight the galaxy in the foreground, which enabled Fu and his team to observe new details of these gas streams. 

Thanks to these bright lights, the team was able to identify that the gas streams had a low concentration of heavy elements, such as aluminum, carbon, iron, and magnesium. This helped the scientists deduce that these cold streams must be coming from outside, instead of being expelled by the star-making galaxy. 

Fu explained just how fortunate the team's timing was "Among the 70,000 starburst galaxies in our survey, this is the only one associated with two quasars that are both nearby enough to probe the halo gas. Even more, both quasars are projected on the same side of the galaxy so that their light can be blocked by the same stream at two different angular distances."

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