ALMA discovers ancient rotating disc galaxy that challenges traditional models

Researchers have made an interesting discovery using the Atacama Large Millimeter/submillimeter Array or ALMA. The discovery is a massive rotating disc galaxy as seen when the universe was only 10% of its current age. The discovery of this galaxy challenges traditional models of galaxy formation.

Galaxy DLA0817g, nicknamed the Wolfe Disk, is the most distant rotating galaxy ever observed. Similar to the Milky Way. Scientists say that previous studies hinted at the existence of early rotating gas-rich disk galaxies, but ALMA allowed unambiguous evidence that they occurred as early as 1.5 billion years after the Big Bang.

Discovery of the Wolfe Disk is challenging many galaxy formation simulations that predict massive galaxies at this point in the evolution of the cosmos grew through mergers of smaller galaxies and hot clouds of gas. The researchers said that most galaxies they discover from the early universe “look like train wrecks” because they went through consistent and often violent merging.

Most galaxy formation simulations show that well-formed disk galaxies only formed around 6 billion years after the Big Bang. The discovery of the Wolfe Disk, when the universe was only 10% of its current age, indicates other growth processes must have dominated. Scientists first discovered the disc in 2017 while examining the light from a more distant quasar.

Light from the quasar was absorbed as it passed through a massive reservoir of hydrogen gas surrounding the galaxy, which was how it was discovered. This particular method is used to find fainter and more “normal” galaxies from the early universe. Scientists say that finding the Wolfe Disk using this method shows that it belongs to the normal population of galaxies present in early times. The team says that observations have shown early rotating disk galaxies are not as rare as they thought, and a lot more of them should be out there.

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