Galaxies In Infant Universe Were Surprisingly Mature, Researchers Say

ARTIST’S ILLUSTRATION OF A DUSTY, ROTATING DISTANT GALAXY
Credit: B. Saxton NRAO/AUI/NSF, ESO, NASA/STScI; NAOJ/Subaru

Astronomers have discovered that massive galaxies were already much more mature in the early universe than previously expected, astronomers announced Tuesday.

The finding was discovered after astronomers performed the first and largest multi-wavelength survey of distant galaxies in the early universe. The survey, called ALPINE, involved two Maunakea Observatories in Hawai‘i – WM Keck Observatory and Subaru Telescope – as well multiple observatories around the world that analyzed a large sample of galaxies located over 12 billion light-years away.

“We didn’t expect to see so much dust and heavy elements in these distant galaxies,” said ALPINE co-principal investigator Andreas Faisst of the California Institute of Technology.

Galaxies are considered more mature when they contain a significant amount of dust and heavy elements (defined by astronomers as all elements heavier than hydrogen and helium), which are considered to be by-products of dying stars. But galaxies in the early universe, researchers explain, have not had much time to build stars yet, so astronomers expect them to be dust-poor and contain a low amount of heavy elements.

However, the ALPINE survey showed relatively grown-up features, particularly a diversity in their structures including the first signs of rotationally supported disks, which may later lead to galaxies with a spiral structure as is observed in galaxies such as our Milky Way.

A majority of the galaxies in the ALPINE survey were chosen from a robust catalog of ultra-distant objects with high-quality spectra obtained using Keck Observatory’s Deep Imaging Multi-Object Spectrograph (DEIMOS).

“Without Keck, ALPINE would not have been made possible,” said Brian Lemaux, an astronomer in the Department of Physics and Astronomy at University of California, Davis and co-investigator of ALPINE. “Much of the science that has resulted from the survey relies heavily on Keck data, which allowed us to target these distant galaxies with ALMA and see what was hidden by dust.”

Researchers are now trying to find out how the galaxies grew up so fast.