Narrow jets of heated plasma blasted out by supermassive black holes at the centers of galaxies reach far beyond their visible edges, according to a study published in the Astrophysical Journal Letters. Led by astronomers Sanchayeeta Borthakur of Arizona State University and Namrata Roy of the Raman Research Institute, researchers found that these powerful particle streams directly impact the circumgalactic medium—a massive reservoir of gas stretching 10 to 20 times the size of the visible galaxy that supplies the raw material for star formation.
Supermassive Black Hole Jets Punch Far Beyond Galactic Disks
How Black Hole Jets Illuminate the Circumgalactic Medium
While supermassive black holes are roughly the size of our solar system, their host galaxies can hold about 100 billion similar systems. Astronomers have long studied how these compact powerhouses affect vast cosmic distances. To track the elusive energy transfer, the research team combined optical data from the Dark Energy Spectroscopic Instrument survey with radio jet measurements from the LOFAR Two-meter Sky Survey.
Because the ionized hydrogen gas, or H-alpha glow, in the circumgalactic medium is extremely faint around any single galaxy, the team averaged observations across hundreds of objects. The resulting data showed that while the gas signal is weak across all directions overall, it becomes clear and bright specifically along the path of the radio jets.
Did you know? A supermassive black hole jet acts less like an ambient lamp shining in all directions and more like a focused beam that heats and ionizes gas directly along its trajectory.
Tracing Cool Gas Versus Ionized Plasma
The study also utilized magnesium absorption signatures to trace cooler gas surrounding the galaxies. Unlike the directional glow detected in H-alpha, the magnesium distribution proved isotropic, showing no specific alignment with the radio jets. This indicates that a uniform cold gas reservoir already surrounds the galaxies on all sides, while the jets specifically heat, brighten, and ionize the gas directly crossing their paths.
Researchers noted that the hydrogen ionization glow reaches peak intensity in two distinct zones: close to the galaxy where the jet first impacts the circumgalactic medium, and near the outer edge where the jet deposits the bulk of its energy.
Controlling Star Formation and Galaxy Evolution
By heating, stirring, and disturbing gas throughout the circumgalactic envelope, these powerful plasma streams prevent the raw material from cooling down and falling inward. This process acts as a brake on star formation, shifting the fate of the host galaxy and potentially making it quiescent over time.
“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, an associate professor in Arizona State University’s School of Earth and Space Exploration.
Frequently Asked Questions
What is the circumgalactic medium (CGM)?
The CGM is a massive envelope of gas wrapping around large galaxies, stretching 10 to 20 times the size of the visible galaxy, and serving as the raw fuel supply for future star formation.
How did astronomers detect the jet impact?
Researchers combined data from the Dark Energy Spectroscopic Instrument survey and the LOFAR Two-meter Sky Survey, analyzing hundreds of galaxies to isolate faint H-alpha hydrogen glow along the radio jet axes.
Why don’t galaxies form even more stars given all their surrounding gas?
Energy and plasma jets from active supermassive black holes heat and disrupt the surrounding gas, preventing it from cooling down and condensing into new stars.
Pro tip: Large-scale astronomical surveys like DESI and LoTSS allow scientists to stack hundreds of weak signals together, revealing patterns that remain invisible in individual galactic observations.
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