(Credit: Waseda University)
TOKYO — Imagine a sprawling cosmic metropolis where ancient galaxies cluster together like skyscrapers in New York City. These galactic cities harbor a mysterious phenomenon: their largest residents have mysteriously stopped growing, their star-forming factories shut down long ago. Now, thanks to NASA’s James Webb Space Telescope (JWST), astronomers may have caught the culprit red-handed — supermassive black holes acting as cosmic kill switches.
A new study published in the Monthly Notices of the Royal Astronomical Society: Letters has revealed compelling evidence of how these cosmic giants might influence galaxy evolution. By examining an ancient “protocluster” called Spiderweb — essentially a galaxy cluster under construction some 11 billion light-years away — researchers have witnessed black holes apparently shutting down star formation in their host galaxies.
Led by Associate Professor Rhythm Shimakawa from Waseda University in Japan, an international team used Webb’s Near Infrared Camera to study 19 massive galaxies within this distant cosmic nursery. What makes this study particularly fascinating is its timing – the researchers are observing these galaxies during the universe’s peak period of star formation, when cosmic construction was in full swing.
The team compared two types of galaxies: those harboring X-ray-emitting black holes and those without. Using Webb’s revolutionary infrared vision, they tracked the distribution of a particular type of hydrogen emission called Paschen-beta, which serves as a celestial beacon indicating where stars are being born.
The results painted a stark picture. Galaxies without active black holes displayed healthy star formation throughout their stellar neighborhoods, much like a thriving city with construction happening in every district. However, their counterparts with X-ray-emitting black holes showed dramatically reduced star formation in their outer regions, as if development had been halted everywhere except the downtown core.
This pattern suggests that supermassive black holes might act like cosmic zoning commissioners, regulating where and when stars can form in their galactic territories. It’s a process astronomers call “AGN feedback,” where active galactic nuclei — the blazing regions around feeding black holes — influence their host galaxies’ evolution through powerful energy outputs.
The findings are particularly significant because they help explain one of astronomy’s enduring mysteries: how do the massive elliptical galaxies we see in today’s galaxy clusters evolve from active, star-forming systems into quiet, “retired” galaxies? The answer, it seems, might lie in the influence of their central black holes.
“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,” says Dr. Shimakawa in a university release.
Paper Summary
Methodology
The researchers used Webb’s NIRCam instrument to observe specific wavelengths of infrared light that correspond to the Paschen-beta emission line, which gets stretched by the universe’s expansion to appear in infrared rather than visible light. They compared these observations with images taken at slightly different wavelengths to measure both the star formation activity and the underlying distribution of existing stars. By stacking images of multiple galaxies together, they could create clearer composite pictures of what typical galaxies look like with and without active black holes.
Key Results
The study found that galaxies with X-ray-emitting black holes had about three times less star formation than their counterparts without active black holes. While normal star-forming galaxies showed evidence of star formation up to about 8,000 light-years from their centers, galaxies with active black holes showed minimal star formation beyond their central regions.
Study Limitations
The study focused on a single protocluster, so the results might not be representative of all galaxy environments. Additionally, the researchers couldn’t measure black hole masses directly, forcing them to use indirect methods to estimate the black holes’ influence. The sample size of 19 galaxies is also relatively small, though significant for such distant objects.
Discussion & Takeaways
This research provides some of the clearest evidence yet for how black holes might influence galaxy evolution. The study suggests that galaxies with more concentrated mass distributions (higher “stellar potentials”) are more likely to show reduced star formation when they harbor active black holes. This might indicate that these galaxies have experienced more black hole activity throughout their history, leading to more accumulated effects on their star formation.
Funding & Disclosures
The research was supported by multiple institutions, including Waseda University, MEXT/JSPS KAKENHI, and various European research programs. The study used data from NASA’s James Webb Space Telescope, which is operated by the Space Telescope Science Institute. The observations were part of JWST’s Cycle-1 program, and the data is publicly available through the Barbara A. Mikulski Archive for Space Telescopes (MAST).
