The research team, led by David Sobral, used special filters to look for a particular wavelength of light called Lyman alpha radiation.
Galaxies that emits radiation are extremely distant. And because of the finite travel time of light, they provide glimpses into the history of the universe. They are thought to be the progenitors of most modern Milky Way-type galaxies.
To find these galaxies, the researchers used 16 different narrow and medium band filters and looked at one of the most widely studied regions of sky outside our Milky Way. This area of the universe has been the focus of the Cosmic Evolution Survey (COSMOS), which probes for signs of galaxy formation and evolution as a function of cosmic time and the local galaxy environment. The field is a small, 2 degree area of the sky located in the direction of the constellation of Sextans.
“We used large amounts of data taken with 16 special filters on wide field cameras and processed them here in Lancaster to literally slice the universe in cosmic time and time-travel to the distant past with 16 well-defined, cosmic-time destinations," said Sergio Santos, another Lancaster University Ph.d. student and team member.
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Researchers are able to date the light from the galaxies because it is stretched by the expansion of the universe, which increases its wavelength, pulling toward the red end of the visible-light spectrum. By measuring the redshift of a galaxy, astronomers can figure out its distance and how long its light has taken to reach us, which tells them how far back they’re peering in time.
The researchers found that star formation evolves by fits and starts.
"These early galaxies seem to have gone through many more ‘bursts’ when they formed stars, instead of forming them at a relatively steady rate like our own galaxy,” Sobral said in a statement. “Additionally, they seem to have a population of young stars that is hotter, bluer, and more metal-poor than those we see today."
Sobral has been studying the early universe for much of his career. In 2015, he led a team that found the first example of a spectacularly bright galaxy within the Epoch of Reionization, which was thought to be home to first generation stars, and a year later, he found similar galaxies made up of the earliest stars.