ALMA and Webb telescope observe most distant galaxy protocluster to date

The James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have helped researchers observe the most distant galaxy protocluster to date.

The research team, led by Assistant Professor Takuya Hashimoto (University of Tsukuba, Japan) and Researcher Javier Álvarez-Márquez (Spanish Center for Astrobiology), first observed the core region of this protocluster, which lies 13.14 billion light-years away, using Webb's Near Infrared Spectrograph (NIRSpec) and found ionized oxygen-ion light ([OIII] 5008 Å) from four galaxies in a quadrangle region measuring 36,000 light-years along a side - that's equal to half the radius of the Milky Way galaxy.

The four galaxies were identified to be 13.14 billion light years away from Earth.

Next, the researchers analysed the archival ALMA data for this region and detected dust emissions from three of the four galaxies, which marks the first detection of dust emission in member galaxies of a protocluster this far back in time.

Scientists believe that cosmic dust in galaxies was supplied by supernova explosions at the end of the evolution of massive stars in the galaxies. The detection of large amounts of dust in a galaxy indicates that many of the first-generation stars in the galaxy have already completed their lives and that the galaxy is expanding.

Further, the team simulated a galaxy formation to theoretically test how the four galaxies in the core region formed and evolved. The findings showed that a region of dense gas particles existed around 680 million years after the Big Bang, and that four galaxies are formed, similar to the observed core region.

The simulation also calculated physical processes such as the kinematics of stars and gas, chemical reactions, star formation, and supernovae, and showed that the four galaxies merge and evolve into a single larger galaxy within a few tens of millions of years.

"We will conduct more sensitive observations of the protocluster A2744z7p9OD with ALMA to see if there are any galaxies that were not visible with the previous sensitivity. We will also apply the JWST and ALMA observations, which have proven to be very powerful, to more protoclusters to elucidate the growth mechanism of galaxies, and to explore our roots in the Universe," said Javier Álvarez-Márquez of the Spanish Center for Astrobiology.