Using the Atacama Large Millimeter/submillimeter Array (ALMA), a large radio observatory in Chile, researchers have taken "baby pictures" of Milky Way-like galaxies when their star formation was just beginning to accelerate. At that time, the universe was nearly two billion years old. Since light moves at a finite speed, looking deep into the universe also means looking back in time, and these young galaxies are about 12 billion light-years away from Earth. The cosmos itself is about 13.8 billion years old.
Looking at two of the ancient galaxies in infrared wavelengths, the researchers saw that very early in the galaxies' development, they had what look like extended discs of hydrogen gas that far outpaced the smaller, star-forming regions within. These galaxies also already had rotating discs of gas and dust, and were forming stars at a relatively rapid pace: up to 100 solar masses (the mass of Earth's sun) per year.
Officially designated ALMA J081740.86+135138.2 and ALMA J120110.26+211756.2, the galaxies were observed using light from two quasars in the background. Quasars are supermassive black holes surrounded by bright accretion discs, and are themselves thought to be the centers of particularly active galaxies.
The glowing carbon also offered another clue to the galaxies' structure, because its position was offset from the hydrogen gases that the astronomers initially saw, as revealed by the quasars' shine. That means that the galaxies' gases extend far from the dense carbon regions, suggesting each galaxy has a large halo of hydrogen encircling it, the researchers said.
Looking at the foreground objects that a shining background quasar could reveal, "we had expected we would see faint emissions right on top of the quasar, and instead we saw bright galaxies at large separations from the quasar," J. Xavier Prochaska, an astrophysicist at the University of California, Santa Cruz, and co-author on the new study, said in a statement.
The data also showed that the young galaxies have already begun rotating, which is a hallmark of spiral galaxies like the Milky Way, the study said.
The effort to find such early stage galaxies began in 2003, when Prochaska first worked on the idea of using the spectra of quasars, the wavelengths of light they emit, to reveal those of galaxies in the foreground. Such arrangements are called damped Lyman-alpha systems, because the hydrogen gas blocks certain wavelengths of light from the quasar, revealing the gas's presence and extent.
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