AZoQuantum spoke with Qiong Li, a Postdoctoral Researcher at the University of Manchester, about her research into the Universe’s earliest large-scale structures. In this interview, Li shares insights into the discovery of JADES-ID1, an exceptionally early protocluster identified through observations from the James Webb Space Telescope (JWST) and Chandra X-ray Observatory. She explains how this finding is challenging long-held views on when and how galaxy clusters first began to form.
Could you please introduce yourself and your current research?
I’m a postdoctoral researcher at the University of Manchester, working on how the earliest large-scale structures in the Universe came together. My research focuses on high-redshift galaxies, protoclusters, and the environments in which galaxies form and evolve, using data from facilities like JWST, HST, Chandra, and other multi-wavelength surveys. Broadly speaking, I’m interested in answering a deceptively simple question: how did today’s massive galaxy clusters start their lives? JADES-ID1 is a particularly exciting piece of that puzzle, because it allows us to watch a cluster in the act of assembling, at a time when the Universe was barely a billion years old.
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Could you briefly walk us through the key steps that helped identify JADES-ID1 as an overdensity of early galaxies?
The process was a bit like detective work. We started by constructing a large, homogeneous sample of nearly 3,000 robust galaxies at z>4.5 using JWST deep-field surveys, combined with HST data. We then quantified each galaxy’s local environment, allowing us to systematically identify overdense regions. JADES-ID1 consistently stood out as one of the strongest overdensities across multiple density estimators and redshift selections. Crucially, this result remained robust under a range of sanity checks, showing that the signal is not driven by selection effects or a few bright sources. From there, we tested whether this overdensity was real or just a statistical fluke. Multiple independent checks all pointed to the same conclusion: this was a genuine structure, not a coincidence. Follow-up spectroscopic confirmation is a major ongoing effort. In practice, it’s very much a “cast a wide net first, then zoom in” strategy.
Which assumptions in current galaxy cluster formation models are most directly challenged by JADES-ID1, and where do you suspect revisions will be needed?
The main challenge is timing. Many models assume that massive, gravitationally bound structures, especially those containing hot X-ray emitting gas, take longer to assemble. JADES-ID1 appears to have reached a surprisingly mature state very early on. This suggests that either structure formation can proceed more rapidly in some regions than we assumed, or that key physical processes, such as gas heating, feedback, or early halo growth, are not fully captured in current models of structure formation.
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From your perspective, what were the most technically demanding aspects of combining the multi-wavelength datasets of JWST’s census and Chandra’s detection of diffuse hot gas to robustly demonstrate that these galaxies are genuinely gravitationally bound?
The hardest part was convincing ourselves, and everyone else, that we were seeing a physical system rather than a lucky alignment. JWST excels at finding faint galaxies, while Chandra traces hot, diffuse gas. These datasets live in very different observational worlds, with different resolutions, noise properties, and selection effects. Carefully matching them required meticulous cross-checks, background modelling, and conservative significance tests. Demonstrating that the X-ray emission truly traces a shared gravitational potential, rather than unrelated foreground or background sources, was particularly demanding.
What do the individual properties of the potential 66 member galaxies within JADES-ID1 tell you about environmental effects already at work in this very young, assembling structure?
Galaxies in overdense regions like JADES-ID1 show higher star formation activity than those in underdense environments, even at fixed stellar mass. Many of them are forming stars more actively, and some show signs of containing more dust and gas. This suggests that even at this very early stage, when the protocluster is still assembling, the environment is already influencing how galaxies grow and evolve. In other words, galaxies don’t evolve in isolation, their surroundings begin to shape them surprisingly early in cosmic history.
How does JADES-ID1 compare to earlier systems without detectable X-ray emitting gas, and what does this tell us about the timeline and physical conditions required for a protocluster to develop a hot intracluster medium?
Many previously known protoclusters are identified purely through galaxy overdensities, without any sign of hot intracluster gas. JADES-ID1 is different because it appears to have crossed a critical threshold. The presence of diffuse X-ray emission may indicate that the system has already begun to virialise, meaning the gas has been heated by the deepening gravitational potential. This tells us that the transition from a loose association of galaxies to a physically bound cluster may happen faster, and earlier, than we thought.
Do you see a unifying physical explanation emerging, for example, related to baryonic physics, dark matter properties, or initial conditions in the early universe?
A likely explanation involves a combination of factors rather than a single dramatic revision of physics. Early-forming dark matter haloes, efficient gas accretion, and strong baryonic processes, such as feedback and shock heating, may all work together to accelerate cluster assembly in certain regions of the early Universe. JADES-ID1 suggests that when the initial conditions are right, structure formation can proceed at an impressive pace.
What are the most important follow-up observations or surveys, either with JWST, Chandra, or future facilities, that you believe are needed to map the full evolutionary path from systems like JADES-ID1 to the mature galaxy clusters we see in the local universe?
Deeper JWST spectroscopy will be crucial to confirm membership and probe the internal dynamics of the system. Looking ahead, wide-field surveys from facilities like Euclid and the Roman Space Telescope will help us to find many more systems like JADES-ID1, placing it into a broader population context. Ultimately, the goal is to trace a continuous evolutionary path, from the earliest protoclusters to the massive galaxy clusters we see in the nearby Universe today.
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About the Speaker
Qiong Li is a postdoctoral researcher at the University of Manchester, where she studies the formation and evolution of galaxies in the early Universe. She received her PhD in astrophysics from Peking University in 2020. Her research uses data from the James Webb Space Telescope to investigate protoclusters and large-scale structures, and how galaxies grow and interact within them shortly after the Big Bang.
References and Further Reading
- Li, Q., Conselice, C. J., Sarron, F., Harvey, T., Austin, D., Adams, N., et al. (2025). Environmental effects on galaxy formation and protocluster galaxy candidates at 4.5 < z < 10 from JWST observations. Monthly Notices of the Royal Astronomical Society, 539(2), 1796–1819. DOI:10.1093/mnras/staf543. https://academic.oup.com/mnras/article/539/2/1796/8105727
- Bogdán, Á., Schellenberger, G., Li, Q., & Conselice, C. J. (2026). An X-ray-emitting protocluster at z ≈ 5.7 reveals rapid structure growth. Nature, 649(8099), 1134–1138. DOI:10.1038/s41586-025-09973-1. https://www.nature.com/articles/s41586-025-09973-1
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