Understanding how galaxies form and complete their growth is an area of fundamental focus in astrophysics. The dense regions of the universe, like galaxy clusters, are dominated by giant elliptical galaxies—massive, ancient galaxies that consist of old stars. Although the mechanism by which these giant elliptical galaxies halt star formation remains debated, one theory predicts that supermassive black holes (SMBHs) could play a key role. Their intense energy can suppress the gas supply to galaxies, which may lead to the formation of the giant elliptical galaxies seen today.
Against this backdrop, an international team of researchers investigated massive galaxies in an ancient galaxy cluster known as the Spiderweb protocluster, located 11 billion light years away (Fig. 1), using data from the James Webb Space Telescope (JWST) . The research was led by Associate Professor Rhythm Shimakawa from Waseda University, Japan; Dr. Yusei Koyama from the National Astronomical Observatory of Japan; Prof. Tadayuki Kodama from Tohoku University, Japan; Dr. Helmut Dannerbauer and Dr. J. M. Perez-Martinez from the Instituto de Astrofísica de Canarias and Universidad de La Laguna, Spain; along with others who were a part of the team. Their findings were published in the Monthly Notices of the Royal Astronomical Society: Letters on December 18, 2024.
The team succeeded in obtaining high-resolution maps of the recombination lines of hydrogen, which indicate the activity of star formation and SMBHs, through the Near-Infrared Camera mounted on JWST. Detailed analysis showed that massive galaxies with active SMBHs exhibit no sign of star formation, meaning that their growth is severely hampered by SMBHs (Fig. 2). The results support the theoretical prediction that the formation of giant elliptical galaxies is linked with SMBH activity in the past.
"The Spiderweb protocluster has been studied by our team for more than 10 years using the Subaru Telescope and other facilities. With the new JWST data, we are now able to 'answer the questions' of understanding and predicting galaxy formation that we have accumulated," remarks Dr. Shimakawa. He adds further, "This study marks a significant step forward in expanding our understanding of the co-evolution of SMBHs and galaxies in celestial cities."
