In a groundbreaking discovery that challenges our understanding of galaxy formation and evolution, scientists using the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA) have unveiled an extraordinary view into the lives of quiescent galaxies just 1 to 2 billion years after the Big Bang. These galaxies, characterized by their unexpectedly rapid formation and quenching, harbor clues that could reshape theories about how galaxies consume and expel the fuel for star formation, molecular gas.
Traditionally, the rapid emergence and cessation of star formation in such massive galaxies have posed a puzzle. Theories often implicate feedback mechanisms from active galactic nuclei (AGN), supermassive black holes at their centers, as key players in regulating star formation through energetic outflows that disperse molecular gas. However, recent observations suggest that these quenching processes may be far more efficient and faster than previously envisaged, prompting researchers to investigate the intricate balance of gas inflow, consumption, and outflow in greater detail.
The subject of this new study is a massive quiescent galaxy known as GS-10578, situated at a redshift of 3.064, meaning we observe it as it was over 11 billion years ago. This galaxy stands out not only due to its mass and rapid evolutionary timescale but also because it harbors an active galactic nucleus driving powerful neutral-gas outflows. ALMA’s deep observations revealed that the mass outflow rate from the AGN is approximately 60 ± 20 solar masses per year, a formidable force capable of influencing the galaxy’s star formation potential dramatically.
Despite hosting such an active nucleus, GS-10578 exhibits a remarkably low star-formation rate, less than 5.6 solar masses per year, confirming its quiescent nature. More strikingly, the galaxy is found to be distinctly gas-poor, with molecular gas mass below 10^9.1 solar masses, constituting less than 0.8 percent of its stellar mass. This low molecular gas fraction is a critical piece of the puzzle since molecular gas acts as the essential fuel from which stars form. The authors’ work places direct constraints on this galaxy’s molecular gas content through CO line observations, providing one of the most precise measurements of its kind in the early universe.
By integrating data from ALMA with complementary observations from JWST, the researchers could reconstruct the gas consumption history of GS-10578. Their analysis reveals a scenario where the galaxy evolved under conditions of net-zero gas inflow—where the amount of gas lost through star formation corresponds closely to the amount missing relative to typical star-forming galaxies at comparable epochs. This observation suggests a delicate balance, implying that the gas reservoir was neither replenished nor over-expelled, but rather balanced by feedback mechanisms with remarkable precision.
Such equilibrium could emerge through two main pathways. First, preventative feedback may have halted further inflow of gas from the galaxy’s surroundings, effectively starving the galaxy and preventing the replenishment of star-forming material. Alternatively, ejective feedback mechanisms—such as the AGN-driven outflows observed—might expel gas at rates closely matched to any incoming gas streams, maintaining a steady state with no net gain or loss over extended periods.
The implications of this study are profound for our understanding of galaxy quenching as a prolonged process rather than an abrupt event. Instead of a single, catastrophic quasar episode rapidly clearing gas and terminating star formation, this evidence points to a sustained regulatory mechanism that maintains quiescence over hundreds of millions of years. Such a scenario demands that models of galaxy evolution accommodate extended periods of finely tuned feedback balancing gas inflow and outflow.
This discovery also sheds light on the complexity of feedback from supermassive black holes. The measured outflow rate of neutral gas exceeds star formation rates by an order of magnitude, highlighting the dominant role of AGN-driven winds in modulating the gas cycle. These winds can expel molecular gas reservoirs or prevent their replenishment, thus halting star formation not by mere exhaustion but by active suppression of gas inflows.
Further insights into GS-10578’s structure also emerge from the data. The galaxy is described as massive and fast-rotating, suggesting a dynamically evolved system. Such rotational support may influence how gas is distributed and removed within the galaxy and its circumgalactic environment. Understanding the interplay between galaxy kinematics and feedback processes is crucial to painting a complete picture of early galaxy evolution.
The ability to observe such a distant, quiescent galaxy and measure its molecular gas is largely thanks to the synergy between JWST and ALMA. JWST offers unprecedented sensitivity and resolution in the near- and mid-infrared, critical for identifying and characterizing high-redshift quiescent systems. ALMA complements these capabilities by probing the cold molecular gas component through millimeter-wave spectroscopy, directly measuring CO emission lines that trace the molecular hydrogen reservoirs vital for star formation.
Moreover, this study exemplifies the evolving narrative around galaxy quenching. Previous assumptions centered on rapid quasar-driven blowouts as the dominant quenching mode are now being reconsidered in favor of models accounting for sustained, multifaceted feedback over long timescales. This nuanced understanding has ripple effects on how we model galaxy populations and their evolution through cosmic history.
The team’s findings also stress the importance of studying individual galaxies in detail rather than relying entirely on statistical population studies. Each galaxy, like GS-10578, provides a unique laboratory for investigating the physics governing star formation, gas cycling, and feedback under extreme conditions. As JWST and ALMA continue to deliver deeper and more precise observations, the census of massive, quiescent galaxies in the early universe will expand, offering further opportunities to refine these emerging models.
Looking forward, exploring whether other quiescent high-redshift galaxies display similar gas consumption histories will be vital for assessing the universality of these mechanisms. It remains an open question if the finely balanced feedback observed here is typical or an exceptional case. Identifying commonalities and differences across the population will help clarify the relative importance of preventative versus ejective feedback and their interrelation with galaxy dynamics.
In conclusion, the joint ALMA and JWST investigation into GS-10578 represents a pivotal step toward unraveling the complex interplay between star formation, gas dynamics, and black hole feedback in the early universe. By revealing a massive, gas-poor galaxy evolving with near-perfect gas inflow and consumption balance, this study reframes the quenching process as an extended, self-regulated phenomenon. This breakthrough underscores the necessity of high-resolution, multiwavelength observations to decode the histories of distant galaxies and promises to drive transformative advances in our comprehension of cosmic galaxy evolution.
Subject of Research: Evolution and gas consumption history of a massive quiescent galaxy at high redshift (z=3.064).
Article Title: Measurement of the gas consumption history of a massive quiescent galaxy.
Article References:
Scholtz, J., D’Eugenio, F., Maiolino, R. et al. Measurement of the gas consumption history of a massive quiescent galaxy. Nat Astron (2026). https://doi.org/10.1038/s41550-025-02751-z
