Young galaxy's halo reveals clues to evolution and growth of ancient galaxies

The halo of a young galaxy Q2343-BX418 could shed light on the evolution and growth of the universe's early galaxies.
By Tyler MacDonald | Jul 25, 2018
Researchers believe that they have discovered a new method of unlocking the mysteries underlying the formation and evolution of the first galaxies. By examining Q2343-BX418, a small young galaxy about 10 billion light years from the Earth, the team believes they can reveal how galaxies looked following the birth of the universe.

Not only that, but the galaxy possesses a gas halo that is emits a certain type of light that is of great interest to astronomers.

"In the last several years, we've learned that the gaseous halos surrounding galaxies glow with a particular ultraviolet wavelength called Lyman alpha emission," said the study's lead author Dawn Erb. "There are a lot of different theories about what produces this Lyman alpha emission in the halos of galaxies, but at least some of it is probably due to light that is originally produced by star formation in the galaxy being absorbed and re-emitted by gas in the halo."

"Most of the ordinary matter in the universe isn't in the form of a star or a planet, but gas," Erb said. "And most of that gas exists not in galaxies, but around and between them."

The halo is the location where gas enters and exits the galaxy. It also fuels galaxies, and sometimes the gas within a galaxy can shift into the halo. The process of gas flowing in and out of these regions is what influences stars and their fates.

"The inflow of new gas accreting into a galaxy provides fuel for new star formation, while outflows of gas limit a galaxy's ability to form stars by removing gas," Erb said. "So, understanding the complex interactions happening in this gaseous halo is key to finding out how galaxies form stars and evolve."

Notably, the study harnessed the power of the Keck Cosmic Web Imager (KCWI) from the Keck Observatory.

"Our study was really enabled by the design and sensitivity of this new instrument," Erb said. "It's not just an ordinary spectrographit's an integral field spectrograph, which means that it's a sort of combination camera and spectrograph, where you get a spectrum of every pixel in the image."

The findings were published in Astrophysical Journal Letters.

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