SPACE/COSMOS
ASU astronomers uncover black hole jets reaching far beyond their galaxies and deciding their fate
Arizona State University
image:
Artist’s illustration of a supermassive black hole at the center of a radio galaxy launching powerful jets (shown in pink) all the way into the galaxy’s CGM. The study finds that these jets do not light up the surrounding gas equally in all directions. Instead, the hydrogen gas glows (shown in red) most strongly along the path of the radio jets. This suggests that black holes can send energy far beyond the galaxy’s center and shape the larger gas reservoir that regulates star formation and fate of galaxies. We use optical data from the DESI survey and radio observations from the LOFAR Two meter Sky Survey (LoTss).
view moreCredit: Image courtesy of Hailey Nelson/ Arizona State University.
Galaxies are enormous and hold hundreds of billions of stars. These stars form from cold, dense gas. Indeed, every large galaxy, including the Milky Way, is wrapped in a huge envelope of gas called the circumgalactic medium, or CGM. This gas is a reservoir of raw material and stretches 10-20 times the size of the visible portion of the galaxy. This CGM gas eventually cools, moves inward into the galaxy, and clumps together to form stars. Thus, the CGM plays a key role in shaping stars, planets, and even life within a galaxy. But astronomers have long puzzled over why, given how much star-forming gas surrounds them, galaxies don't have even more stars. What is keeping the fuel from cooling down and forming those stars?
A new study led by astronomers Sanchayeeta Borthakur of Arizona State University (ASU) and Namrata Roy, now at the Raman Research Institute (RRI), found evidence that narrow jets of heated plasma, blasted out by the supermassive black holes at galaxies' centers, can affect the whole galaxy even beyond what we can see, and may shape its future. The jets may reach out and disrupt the gas that galaxies need to keep growing. Their research has been published in the Astrophysical Journal Letters.
“This is a pathbreaking result that solves the long-standing mystery of how black holes influence galaxies, their stars, and life as we know it!” said Borthakur, Associate Professor in ASU’s School of Earth and Space Exploration. “This work opens a new direction to explore further the intricacies of the connection between the supermassive black holes trillions of miles from where we are to how we came to be here.”
Little in size, big in influence
When a black hole actively feeds on gas, it can release enormous energy that heats the surrounding gas. Even though these black holes can be powerhouses of energy, they are quite small and are roughly about the size of our solar system. On the other hand, their host galaxies can hold about 100 billion such solar systems.
“The surprising question is: how can something so small energetically impact something so enormous?” said Roy, assistant professor at RRI and former ASU Exploration Prize Postdoctoral Fellow.
One way to envision it is to think of an ant leaving its impression hundreds or thousands of kilometers away. Scientists still do not fully understand how energy from these active black holes reaches such distances and changes along the way.
The team’s study provides evidence as to how this could occur. They focused on active black holes that emit strong jets, which are narrow streams of hot, fast-moving plasma shooting out far beyond a galaxy’s visible edge. They looked for a distinct imprint in the ionization state of the gaseous reservoir caused by these jets. The ionized gas, or the “glow” from hydrogen gas they were looking for in the CGM, is so faint that no single galaxy would show it clearly. Hence, the team combined observations of hundreds of galaxies with active jets, using data from the Dark Energy Spectroscopic Instrument (DESI) survey and radio jet measurements from the LOFAR Two-meter Sky Survey (LoTSS). They combined measurements coming from the direction of the jet axes and searched for a specific telltale sign of ionized hydrogen gas along the jet path, known as H-alpha.
Roy, Borthkur and colleagues showed that when averaged over all directions around the galaxies, the signal was weak; however, along the radio jets, the H-alpha signal became clear and strong. This indicates that the gas does not glow uniformly everywhere but is particularly bright along the jet path. A simple analogy is that the jet acts less like a lamp shining in all directions, and more like a powerful beam that makes the gas glow where it passes through.
These findings show that black-hole jets do not affect the gas surrounding galaxies equally in all directions; instead, they leave a distinct impression by causing the gas to shine and become ionized mainly along the radio jet's path. They also found that the jets have the biggest impact, and that the glow from ionized hydrogen is brightest in two places: close to the galaxy where the jet first hits the CGM, and much farther out near the CGM’s outer edge, where the jet releases most of its energy. This provides a clear signature of how jets can illuminate or disrupt the surrounding gas, even at great distances, all the way to the CGM. This mechanism helps shape the galaxy's environment, influence its growth and evolution - it determines whether the galaxy continues to form stars or becomes quiescent.
“What excites me most is the scale of the connection,” Roy said. “A black hole is incredibly small compared to a galaxy, but its impact can reach hundreds of thousands of light-years, far into the galaxy’s outer reaches. The jet carries the energy outward, and the gas lights up along its path.
”As a check, the team also examined a tracer of cooler gas via the absorption signature of magnesium. Unlike the directional glow in H-alpha, Magnesium was more widely distributed isotropically and did not show any connection to the jet direction. This implies that the cool gas component might already exist as a reservoir surrounding the galaxy uniformly on all sides. Yet the jet brightens, heats, and ionizes gas along its own path, lighting up a trail and causing it to glow in H-alpha.
Black holes determine a galaxy's fate.
The findings offer some of the clearest evidence yet for how a black hole can affect galaxies far beyond its central region. By heating, stirring, and disturbing gas throughout the CGM, jets can prevent that gas from cooling down and falling inward to fuel new stars. This acts as a brake on the galaxy’s growth, changes its fate, and makes it much less active in star formation.
This means the black hole is not just “feeding” at the center of the galaxy, as some might think. It also reaches out and changes the galaxy’s environment, which can eventually change its fate.
Specific Directions: Look both ways on the path
Past studies searched for the signal but couldn't detect it, making this directional discovery an exciting breakthrough. The signal only appears when we look along the jet direction. If the astronomers had thought the CGM was the same in every direction, the team would have missed this discovery. The jet ionizes hydrogen gas along its path, making it glow in H-alpha in a very specific direction.
This study shows the value of large optical and radio surveys like the Dark Energy Spectroscopic Instrument (DESI) survey and the LOFAR Two-meter Sky Survey (LoTss). By combining many weak signals, astronomers can now study the behavior of galaxies that would otherwise stay hidden. The study also gives astronomers and theorists a new way to test how black-hole jets affect galaxies.
Contributing co-authors include Timothy Heckman at Johns Hopkins University and Tanmay Singh at Arizona State University.
This work is supported by NASA, STScI, and NSF.
Journal
The Astrophysical Journal Letters
Method of Research
Observational study
Subject of Research
Not applicable
Article Publication Date
24-Sep-2026
JWST finds early galaxies were already seeding the universe with heavy elements
Early galaxies were already seeding the cosmos with heavy elements, such as oxygen and carbon, just 500 million years after the Big Bang
image:
Artist’s visualization of an early galaxy and its surrounding gaseous environment. The orange structures represent metal-enriched gas being expelled from the galaxy, illustrating how young galaxies began dispersing heavy elements into their surroundings within the Universe’s first 500 million years. The visualization is based on publicly available FIRE-2 cosmological simulation data and is not a direct telescope image.
view moreCredit: Yongda Zhu
When the universe was still in its infancy – only 500 million years after the Big Bang or about 3% of its current age – some of the universe's earliest stars and galaxies had already formed. Astronomers have long predicted that much of the gas surrounding these young galaxies must have remained rather pristine, composed of mostly hydrogen and helium, the primordial ingredients available in the newborn cosmos.
According to a study published by astronomers at the University of Arizona in Nature Astronomy, this picture likely is not correct. Instead, galaxies were already seeding the cosmos with heavy elements, such as oxygen and carbon, much earlier than astronomers expected.
"We observed that heavy elements escaped from galaxies very, very early in cosmic time," said Yongda Zhu, first author of the paper and postdoctoral researcher at the U of A Department of Astronomy and Steward Observatory. "Not only were the galaxies producing these elements, but they were also dispersing them, possibly seeding other galaxies."
How the universe got its elements
In the early universe, the cosmos barely contained anything other than hydrogen and helium, the two simplest elements occupying the very top of the periodic table. Over time, gravity pulled clouds of these simple elements together to form stars, where the immense pressures and temperatures inside allowed nuclear fusion and other reactions to forge more complex, heavier elements such as carbon and oxygen.
When stars burned out or ended their lives as supernovae, they shed these heavy elements into space, where they became the building blocks for future generations of stars, planets and ultimately, life. Even the carbon in our bodies and the oxygen we breathe were forged in earlier generations of stars.
Until now, however, it wasn't clear how and when heavier elements were transported from the earliest galaxies into the surrounding universe.
Looking at early galaxies
Zhu's research centered on three early galaxies whose light has traveled for more than 13 billion years, showing them as they appeared about 500 million years after the Big Bang, during a cosmic period known as the Epoch of Reionization. At that time, the first generations of stars and galaxies were transforming the early universe by ionizing the hydrogen gas between them. This process, during which electrons were stripped from their hydrogen nuclei, gradually brought an end to the cosmic "dark ages" by allowing ultraviolet light to travel more freely through the universe.
"We used the galaxies themselves as background light sources," said Zhu. "As light from the galaxies traveled toward Earth, it passed through surrounding gas, and we were able to look at the light's absorption patterns to detect specific elements."
Observations of these ancient galaxies were only made possible by the infrared capabilities of NASA's James Webb Space Telescope, which allowed the researchers to observe galaxies as they appeared about 13 billion years ago. The nearly 30 hours of exposure provided enough light to detect faint absorption patterns in the spectra of these distant galaxies.
Over the course of one long night, Zhu manually searched through publicly available JWST spectra from hundreds of galaxies and pinpointed three with absorption patterns indicating the presence of heavy elements, including carbon, oxygen and silicon. The absorption lines were "blueshifted" relative to the galaxies' redshift, indicating that the gas was moving outward from the galaxies and carrying oxygen, carbon and other heavy elements into intergalactic space.
The chemical fingerprints of these infant galaxies closely resembled those of evolved galaxies billions of years later, providing evidence that even at cosmic dawn, galaxies were already producing and spreading heavy elements into the space around them.
"Think of these elements, which originated from the galaxies' stars, as food dye dropped into a cup of water," said Zhu. "The color begins to spread through the water, and, in a similar fashion, these heavy elements from early galaxies began to escape into space and 'enrich' their surroundings."
Baryon Cycling
The process by which galaxies exchange material is known as baryon cycling. It is one reason galaxies are not isolated systems, but interconnected parts of a larger galactic ecosystem. Material produced by one generation of stars can be recycled and redistributed through this galactic ecosystem.
The discovery of early baryon cycling may also help explain why astronomers have struggled to find the first generation of stars, known as Population III stars. These stars are thought to have been the very first stars formed from pristine gas containing only hydrogen and helium, before heavier elements had been produced and dispersed throughout the universe. If galaxies were already enriching their surroundings only 500 million years after the Big Bang, truly pristine gas – and the Population III stars that formed from it – simply may not have been around long enough to be observed.
"If you start out with pure vanilla ice cream but start mixing in sprinkles soon after, it won't be long until you can no longer find any pristine, plain, vanilla ice cream,” Zhu said.
Journal
Nature Astronomy
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
Early metal-enriched baryon cycling before the midpoint of cosmic reionization
Article Publication Date
24-Sep-2026
No comments:
Post a Comment