Baby dwarf galaxies, also called green pea galaxies, were likely the cause of the universe's heating approximately 13 billion years ago, according to new research by University of Virginia scientists. The findings may help shed light on the processes that took place during the earliest years of the universe.
After the Big Bang, the universe was a hot, dense state of matter that was ionized until about 380,000 years later, when it expanded enough to cool and become neutral and house the creation of the first structures - clouds of hydrogen gas and helium, which eventually became stars. However, about one billion years after the Big Bang, the universe reheated and hydrogen became ionized yet again, an event that has caused much debate in the field.
The team used data gathered from the Hubble Space Telescope's ultraviolet spectrometer and found a compact dwarf galaxy that was releasing a high amount of ionizing photons into the space between galaxies, photons that they believe were the cause of the universe's reionization.
"This galaxy appears to be an excellent local analog of the numerous dwarf galaxies thought to be responsible for the reionization of the early universe," Trinh Thuan, co-author of the study, said in a press release. "The finding is significant because it gives us a good place to look for probing the reionization phenomenon, which took place early in the formation of the universe that became the universe we have today."
In order for reionization to occur, galaxies must release photons into the intergalactic space that lies between other galaxies. Thus far, no one has been able to find a galaxy capable of releasing enough ionizing radiation, until now.
"As we make additional observations using Hubble, we expect to gain a much better understanding of the way photons are ejected from this type of galaxy, and the specific galaxy types driving cosmic reionization," Thuan said. "These are crucial observations in the process of stepping back in time to the early universe. They paved the way to future observations with the successor of Hubble, the James Webb Space Telescope, planned for launch in 2018, which is expected to revolutionize the field with updated capabilities for detailing the first galaxies and sources of cosmic re-ionization."
The findings were published in the Jan. 13 issue of Nature.
