The menagerie of galaxies we see in the universe today is the product of the assembly and evolution of clumps of matter over millions of years. But the exact timings and the exact mechanisms for galaxy formation remain nebulous.
A literal light in the dark comes from the emission of certain distant galaxies. An international team has used this light to measure the rotation of these galaxies, discovering a large population of disk-shaped galaxies already in place a billion years after the Big Bang, much earlier than thought. The findings are reported in The Astrophysical Journal.
Thanks to observations using the Atacama Large Millimeter/submillimeter Array (ALMA), the research revealed rotating mangled galaxies as well as perfectly smooth ones. The former are probably the consequence of mergers and interactions, while the latter were likely formed by a different slower and less chaotic process.
Around 15 percent of the galaxies observed were smooth rotators, with properties similar to those expected of spiral galaxies in the more recent universe. This doesn’t mean they are spiral galaxies in the modern sense, but it could suggest that either or both mechanisms are key steps to producing a spiral galaxy like our own Milky Way.
"We are finding nicely ordered rotating galaxies at this very early and quite turbulent stage of our universe," lead author Andreas Faisst, from Caltech, said in a statement. "That means they must have formed by a smooth process of gathering gas and haven't collided with other galaxies yet, as many of the other galaxies have."
The observations were part of the ALPINE Survey (ALMA Large Program to Investigate C+ at Early Times), combining ALMA’s detection with other telescopes such as Hubble and the now-defunct Spitzer to provide the first multi-wavelength study of galaxies as they were between 1 billion and 1.5 billion years after the Big Bang.
This approach, together with upcoming powerful new observatories, will be even better at being able to characterize these primordial galaxies and help us understand how they change over the ages of the universe.
"How do galaxies grow so much so fast? What are the internal processes that let them grow so quickly? These are questions that ALPINE is helping us answer," says Faisst. "And with the upcoming launch of NASA's James Webb Space Telescope, we will be able to follow-up on these galaxies to learn even more."