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Green pea galaxies could help understand formation of early universe

Last Updated: Thursday, April 4, 2013 - 15:20

Washington: The rare Green Pea galaxies that were discovered by the general public in 2007 could help confirm astronomers` understanding of reionization - a pivotal stage in the evolution of the early universe, according to a new study.

Reionization occurred a few hundred million years after the Big Bang as the first stars were turning on and forming the first galaxies.

During this period, the space between the galaxies changed from an opaque, neutral fog to a transparent charged plasma, as it is today. Plasma is gas that`s electrically charged.

As for how this happened, the prevailing theory holds that massive stars in the early galaxies produced an abundance of high-energy ultraviolet light that escaped into intergalactic space.

There, the UV light interacted with the neutral hydrogen gas it met, blasting electrons off the hydrogen atoms and leaving behind a plasma of negatively-charged electrons and positively charged hydrogen ions.

"We think this is what happened but when we looked at galaxies nearby, the high-energy radiation doesn`t appear to make it out. There`s been a push to find some galaxies that show signs of radiation escaping," Anne Jaskot, a doctoral student in astronomy said.

Jaskot and Sally Oey, an associate professor of astronomy in the College of Literature, Science and the Arts, have found that the Green Peas could hold that evidence.

"The Green Peas are compact, highly star-forming galaxies that are very similar to the early galaxies in the universe," Jaskot said.

"Our analysis shows they may be leaking ionizing radiation," she said.

The researchers focused on six of the most intensely star-forming Green Pea galaxies, which are between one billion and five billion light-years away.

They studied their emission lines as observed by the Sloan Digital Sky Survey.

Emission lines show how light interacts with matter, and in this case, they helped the astronomers understand the relationship between the stars and gas in these galaxies.

Their findings are published in The Astrophysical Journal.


First Published: Thursday, April 4, 2013 - 15:19
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