A team led by Sanchayeeta Borthakur of Arizona State University and Namrata Roy, now an assistant professor at the Raman Research Institute and a former ASU Exploration Prize Postdoctoral Fellow, has found evidence that narrow jets of heated plasma, blasted out by supermassive black holes, can reach far beyond the visible boundaries of their host galaxies and disrupt the gas those galaxies need to keep growing. The research, published in The Astrophysical Journal Letters, offers some of the clearest evidence yet that black holes can influence galactic environments on scales hundreds of thousands of light-years across, far beyond the compact region where the black hole itself resides.

The scale mismatch at the heart of this problem is staggering. A supermassive black hole, even an actively feeding one, occupies a region roughly the size of our solar system. Its host galaxy, by contrast, can contain around one hundred billion solar systems worth of stars and gas. When such a black hole feeds on infalling matter, it releases enormous amounts of energy that heat the surrounding gas, but how that energy travels outward and affects structures millions of times larger has remained one of the most persistent puzzles in astrophysics. Roy has compared the challenge to imagining an ant leaving its impression hundreds or thousands of kilometers away, a vivid illustration of just how disproportionate the influence appears to be.

The answer, according to the new work, lies in the jets themselves. Active black holes that emit strong jets launch narrow streams of hot, fast-moving plasma that shoot out far beyond a galaxy’s visible edge. Rather than spreading their energy equally in all directions, these jets act less like a lamp illuminating a room and more like a powerful beam that leaves a glowing trail wherever it passes. The team hypothesized that if jets truly penetrate the circumgalactic medium, they should leave a distinct imprint in the ionization state of the surrounding gas, a chemical and physical fingerprint written along the jet’s path.

Detecting that fingerprint was far from straightforward. The glow of ionized hydrogen in the CGM, observed through a specific emission feature known as H-alpha, is so faint that no single galaxy could reveal it clearly. To overcome this limitation, the researchers combined observations of hundreds of galaxies with active jets, drawing optical data from the Dark Energy Spectroscopic Instrument, or DESI, survey and radio jet measurements from the LOFAR Two-meter Sky Survey, known as LoTSS. By stacking the signals from many galaxies and aligning them along the directions of their radio jets, the team could search for a coherent H-alpha signal that would otherwise remain buried in noise.

The result was striking. When the stacked signal was averaged over all directions around the galaxies, it was weak and inconclusive. But when the astronomers looked specifically along the axes of the radio jets, the H-alpha signal became clear and strong. This directional pattern demonstrates that the gas does not glow uniformly around these galaxies; instead, it shines most brightly precisely where the jets pass through it. The jet ionizes hydrogen gas along its trajectory, lighting up a trail that extends deep into the circumgalactic medium and providing direct evidence that black hole energy reaches and transforms gas at enormous distances from the galactic center.

The study also mapped where the glow was strongest, and the answer revealed two distinct hotspots. The ionized hydrogen emission peaked close to the galaxy, where the jet first slams into the circumgalactic medium, and again much farther out near the CGM’s outer edge, where the jet deposits most of its remaining energy. This double-peaked structure offers a clear physical signature of how jets interact with their surroundings as they bore outward, illuminating and disrupting gas all the way from the inner boundary of the CGM to its farthest reaches.

As a crucial check on their interpretation, the team examined a completely different tracer: the absorption signature of magnesium, which traces cooler gas in the same regions. Unlike the strongly directional H-alpha glow, the magnesium signal was distributed isotropically, appearing equally in all directions with no connection to the jet orientation. This contrast suggests that the cool gas reservoir already surrounds the galaxy uniformly on all sides, while the jet selectively brightens, heats, and ionizes gas only along its own path. In other words, the jets are not creating the reservoir, but they are actively transforming it, carving an energized channel through an otherwise symmetric halo of fuel.

These findings carry profound implications for how galaxies live and die. By heating, stirring, and disturbing gas throughout the circumgalactic medium, jets can prevent that gas from cooling down and falling inward to fuel new stars. The mechanism acts as a brake on galactic growth, throttling star formation and potentially pushing a galaxy from an active, star-forming state into quiescence. The black hole, in this picture, is not merely a passive engine feeding at the center of its galaxy; it reaches outward and reshapes the galaxy’s entire environment, and in doing so it helps determine whether the galaxy continues to build stars or fades into quiet retirement. This feedback loop may finally explain why galaxies have not converted their abundant surrounding gas into far more stars than observations show.

The directional nature of the discovery is itself a methodological breakthrough. Previous searches for this signal failed to detect it, and the new study suggests why: the signal only appears when observations are aligned with the jet direction. Had the team assumed the circumgalactic medium was identical in every direction, the effect would have been averaged away and lost forever. The work also underscores the growing power of large optical and radio surveys such as DESI and LoTSS, which allow astronomers to combine many weak signals into detections of galactic behavior that would otherwise remain hidden. For theorists and observers alike, the result opens a new way to test how black hole jets affect galaxies, and, as Borthakur noted, a new direction for exploring the intricate connection between supermassive black holes trillions of miles away and the conditions that made life on Earth possible. Co-authors on the study include Timothy Heckman of Johns Hopkins University and Tanmay Singh of Arizona State University, with support from NASA, the Space Telescope Science Institute, and the National Science Foundation.

Subject of Research: The directional impact of supermassive black hole jets on the circumgalactic medium and galaxy evolution

Article Title: ASU astronomers uncover black hole jets reaching far beyond their galaxies and deciding their fate

Article References: ASU astronomers uncover black hole jets reaching far beyond their galaxies and deciding their fate. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: supermassive black holes, black hole jets, circumgalactic medium, galaxy evolution, H-alpha emission, ionized gas, DESI survey, LOFAR, star formation, radio galaxies, astrophysics, galactic feedback

The key observable is the dispersion measure, a quantity derived from the tiny frequency-dependent delay imposed on a radio burst as it traverses ionized gas. Because free electrons slow lower-frequency radio waves slightly more than higher-frequency ones, each burst arrives smeared across a characteristic sweep, and the total delay encodes the column density of electrons along the line of sight. After subtracting the contribution of our own Milky Way and the burst’s host galaxy, the remaining extragalactic dispersion measure is a direct tally of the ionized baryons lying between the source and the observer — gas threaded through the intergalactic medium, the circumgalactic halos of intervening galaxies, and the hot atmospheres of groups and clusters. This is precisely the baryonic material whose distribution has been sculpted by supernova explosions, jets from supermassive black holes, and other feedback processes that blow gas out of galaxies and redistribute it across megaparsec scales.

That redistribution matters enormously for cosmology. Surveys of weak gravitational lensing — the subtle distortion of galaxy images by intervening matter — measure the clustering of all matter, dark and luminous alike, on these same scales. But the theoretical predictions that lensing measurements are compared against must account for how feedback expels gas from dark matter halos, smoothing the matter distribution and suppressing the amplitude of the matter power spectrum on small scales. If that suppression is mis-modeled, inferred cosmological parameters such as the clumpiness of matter, the sum of neutrino masses, and the properties of dark energy can all be biased. Until now, the primary probes of this baryonic physics have been X-ray observations of hot gas and the Sunyaev–Zel’dovich effects, in which hot electrons leave signatures in the cosmic microwave background. Both approaches, however, have faced tensions and systematics, particularly in galaxy groups and lower-mass clusters.

The new analysis demonstrates that fast radio bursts are already competitive with the legacy measurements from the Atacama Cosmology Telescope and the eROSITA X-ray telescope. Using a halo-model inference framework calibrated on hydrodynamical simulations, the team converted the observed dispersion measures of 114 bursts into constraints on the gas content of dark matter halos more massive than about 10¹³ solar masses, and on the degree to which feedback suppresses the matter power spectrum. The framework builds on the well-established Macquart relation, the observed linear trend between a burst’s dispersion measure and its redshift, which was previously used to account for the Universe’s so-called missing baryons. Here the authors went a step further, treating the scatter and fluctuations around that relation as a signal of how baryons are distributed within and around halos.

Technically, the inference proceeds by modeling gas profiles within halos using flexible analytic prescriptions whose parameters — including a characteristic feedback mass scale and the radial extent of gas ejected from halos — are constrained through a Markov Chain Monte Carlo fit to the burst sample. A critical systematic is the dispersion measure contributed by each burst’s own host galaxy, which the team treated as a nuisance parameter, allowing its mean and scatter to float in the fit. Robustness tests splitting the sample into lower- and higher-redshift subsets, and allowing the host contribution to evolve with the cosmic star formation history, showed that the inferred feedback constraints are stable across all configurations, indicating that uncertainties about host galaxies do not drive the result. Lower-redshift bursts in the sample anchor the dispersion measure–redshift relation and pin down the host distribution, while higher-redshift bursts sharpen the sensitivity to feedback physics.

The measurements reveal clear signatures of efficient gas expulsion from massive halos, quantified as a suppression of the matter power spectrum at wavenumbers between roughly 0.1 and 3 h Mpc⁻¹ — the regime where weak lensing surveys are most sensitive to baryonic effects and where existing X-ray and thermal Sunyaev–Zel’dovich measurements have disagreed. By constraining the gas mass fraction within group- and cluster-scale halos, the burst data provide an independent check on the scaling relations that underpin cluster cosmology, and they help arbitrate the tensions that have emerged between different baryon surveys. The result establishes fast radio bursts as a genuinely new probe of feedback-regulated structure formation, complementary to lensing, X-ray and microwave-background methods because it is sensitive to all ionized gas regardless of its temperature.

The implications extend beyond astrophysics into fundamental physics. Because baryonic feedback and cosmology are partially degenerate in lensing measurements, independently constraining feedback breaks those degeneracies and sharpens cosmological inference. Forecast analyses accompanying the study show that combining fast radio burst dispersion statistics with weak lensing from a survey like the Vera C. Rubin Observatory’s Legacy Survey of Space and Time — through dispersion-galaxy and dispersion-shear cross-correlations — would tighten constraints on the feedback mass scale dramatically and propagate into substantially improved limits on the sum of neutrino masses and on dynamical dark energy parameters. In an era when percent-level control of baryonic physics is a prerequisite for precision cosmology, a probe that measures the baryons directly and independently is a valuable asset.

The field is poised for rapid growth. Instruments now coming online, including the Deep Synoptic Array, the Canadian Hydrogen Observatory and Radio-transient Detector, and CHIME/FRB with its outrigger stations, are expected to deliver localized bursts at rates hundreds of times higher than current samples, extending the redshift baseline and improving the statistical power of dispersion-based probes. The authors’ forecasts indicate that within the next decade, fast radio bursts could deliver leading constraints on baryonic physics, rivalling or exceeding the multi-probe combinations that currently define the field. As sample sizes grow, the same data will also refine our understanding of the bursts’ own progenitors and host galaxy populations, closing the loop between astrophysics and cosmology in a single dataset.

For now, the result stands as a striking demonstration of scientific serendipity: signals once dismissed as inexplicable flashes of radio noise have become a census of the invisible matter that threads the Universe, revealing not only where cosmic matter resides, but how the explosive feedback of galaxies has smoothed it away. In revealing the suppressed clustering of matter through the electrons it left behind, 114 fleeting radio flashes have delivered a measurement that decades of X-ray and microwave observations have struggled to pin down — and they promise much more to come.

Subject of Research: Using fast radio burst dispersion measures to quantify baryonic feedback and the suppression of the matter power spectrum in structure formation.

Article Title: Signatures of suppressed matter clustering revealed by fast radio bursts

Article References: Sharma, K., Krause, E., Ravi, V., Connor, L., Anbajagane, D., & Rajendra Singh, P. (2026). Signatures of suppressed matter clustering revealed by fast radio bursts. Nature Astronomy. https://doi.org/10.1038/s41550-026-02957-9

Image Credits: AI Generated

DOI: 10.1038/s41550-026-02957-9

Keywords: fast radio bursts, cosmology, baryonic feedback, matter power spectrum, weak lensing, galaxy clusters, dispersion measure, dark matter halos, missing baryons, Sunyaev–Zel'dovich effect, large-scale structure, Nature Astronomy