ALMA Discovers Massive Rotating Disk in Early Universe

Artist impression of the Wolfe Disk, a massive rotating disk galaxy in the early, dusty universe. The galaxy was initially discovered when ALMA examined the light from a more distant quasar (top left).
(Image: NRAO / AUI / NSF, S. Dagnello)
Artist impression of the Wolfe Disk, a massive rotating disk galaxy in the early, dusty universe. The galaxy was initially discovered when ALMA examined the light from a more distant quasar (top left). (Image: NRAO / AUI / NSF, S. Dagnello)

In our 13.8 billion-year-old universe, most galaxies, like our Milky Way, form gradually, reaching their large mass relatively late. But a new discovery made with the Atacama Large Millimeter/submillimeter Array (ALMA) of a massive rotating disk galaxy, seen when the universe was only 10 percent of its current age, challenges the traditional models of galaxy formation.

ALMA radio image of the Wolfe Disk, seen when the universe was only ten percent of its current age. (Credit: ALMA (ESO/NAOJ/NRAO), M. Neeleman; NRAO/AUI/NSF, S. Dagnello)

ALMA radio image of the Wolfe Disk, seen when the universe was only 10 percent of its current age. (Image: ALMA (ESO / NAOJ / NRAO), M. Neeleman; NRAO / AUI / NSF, S. Dagnello)

Galaxy DLA0817g, nicknamed the Wolfe Disk after the late astronomer Arthur M. Wolfe, is the most distant rotating disk galaxy ever observed. The unparalleled power of ALMA made it possible to see this galaxy spinning at 170 miles (272 kilometers) per second, similar to our Milky Way. Lead author Marcel Neeleman of the Max Planck Institute for Astronomy in Heidelberg, Germany, said:

How did the Wolfe Disk form?

The discovery of the Wolfe Disk provides a challenge for many galaxy formation simulations, which predict that massive galaxies at this point in the evolution of the cosmos grew through many mergers of smaller galaxies and hot clumps of gas. Neeleman explained:

In most galaxy formation scenarios, galaxies only start to show a well-formed disk around 6 billion years after the Big Bang. The fact that the astronomers found such a disk galaxy when the universe was only 10 percent of its current age, indicates that other growth processes must have dominated.  J. Xavier Prochaska, of the University of California, Santa Cruz and co-author of the paper, which was published in the journal Nature, said:

Star formation

The team also used the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and the NASA/ESA Hubble Space Telescope to learn more about star formation in the Wolfe Disk.

The Wolfe Disk as seen with ALMA (right - in red), VLA (left - in green) and the Hubble Space Telescope (both images - blue). In radio light, ALMA looked at the galaxy’s movements and mass of atomic gas and dust and the VLA measured the amount of molecular mass. In UV-light, Hubble observed massive stars. The VLA image is made in a lower spatial resolution than the ALMA image, and therefore looks larger and more pixelated. (Credit: ALMA (ESO/NAOJ/NRAO), M. Neeleman; NRAO/AUI/NSF, S. Dagnello; NASA/ESA Hubble)

The Wolfe Disk as seen with ALMA (right – in red), VLA (left – in green) and the Hubble Space Telescope (both images – blue). In radio light, ALMA looked at the galaxy’s movements and mass of atomic gas and dust and the VLA measured the amount of molecular mass. In UV-light, Hubble observed massive stars. The VLA image is made in a lower spatial resolution than the ALMA image, and therefore looks larger and more pixelated.
(Credit: ALMA (ESO/NAOJ/NRAO), M. Neeleman; NRAO/AUI/NSF, S. Dagnello; NASA/ESA Hubble)

In radio wavelengths, ALMA looked at the galaxy’s movements and mass of atomic gas and dust while the VLA measured the amount of molecular mass – the fuel for star formation. In UV-light, Hubble observed massive stars, Prochaska explained:

A ‘normal’ galaxy

The Wolfe Disk was first discovered by ALMA in 2017. Neeleman and his team found the galaxy when they examined the light from a more distant quasar. The light from the quasar was absorbed as it passed through a massive reservoir of hydrogen gas surrounding the galaxy – which is how it revealed itself.

Rather than looking for direct light from extremely bright, but more rare galaxies, astronomers used this ‘absorption’ method to find fainter, and more ‘normal’ galaxies in the early universe, Neeleman said:

Joe Pesce, astronomy program director at the National Science Foundation, which funds the telescope, said:

Provided by: National Radio Astronomy Observatory [Note: Materials may be edited for content and length.]

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