Surprisingly Mature Galaxies Discovered in Our Early Universe with Herschel
It turns out that at least a few galaxies may have been far more mature than expected in the early universe. Using Herschel, scientists have discovered that a few years after the Big Bang, some galaxies were rotating in a mature way, seemingly having completed the accumulation of their gas reservoirs.
When galaxies first form, they accumulate mass by gravitationally attracting external gas clouds. These gas clouds are drawn toward the galaxy and then fall into haphazard orbits. These disordered paths can cause turbulence and ultimately drive star formation.
"The purpose of this project is to study the physical conditions of gas in those galaxies," said James Rhoads, one of the researchers, in a news release. "We wanted to know: are they similar to the galaxies around us or is there some difference in their physical conditions."
In this case, the researchers decided to study two young galaxies known as S0901 and Clone. Located about 10 billion light years away, these galaxies were average for their time in cosmic history. In order to actually study them in depth, though, the researchers had to employ gravitational lensing. What they found was unusual.
"Usually, when astronomers examine galaxies at this early era, they find that turbulence plays a much greater role than it does in modern galaxies," said Rhoads in a news release. "But S0901 is a clear exception to that pattern, and the Clone could be another."
About 10 billion years ago, galaxies were making stars far more actively than they do now. This caused them to show more turbulence in general. Yet it seems this wasn't the case for these two galaxies.
"But here we have cases of early galaxies that combine the 'calm' rotation of a modern one with the active star formation of their early peers," said Sangeeta Malhotra, one of the researchers, in a news release. "This suggests first that these galaxies have finished accumulating their gas, at least for now. But also seems that turbulence is not actually required to trigger that early, active star formation."
The findings reveal a little bit more about our early universe. As astronomers continue to use gravitational lensing in order to peer back in time, they'll likely make further discoveries about the young galaxies that formed just after the Big Bang.
The findings are published in The Astrophysical Journal.