Supermassive Black Holes Are Quietly Strangling Star Formation Across Entire Galaxies

A Tiny Powerhouse With an Enormous Reach

A team of scientists has discovered observational evidence of how supermassive black holes lying at the very centers of galaxies impact the entire galaxy within and beyond its visible boundary — and may dictate their ultimate fate. The finding reframes how astronomers think about black holes: not just as exotic, destructive objects, but as the quiet architects of cosmic evolution.

Even though these black holes can be powerhouses of energy, they are roughly about the size of our solar system — while 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 Namrata Roy, assistant professor at the Raman Research Institute and former ASU Exploration Prize Postdoctoral Fellow.

The Hidden Gas Reservoir That Feeds the Stars

Every large galaxy, including the Milky Way, is wrapped in a huge envelope of gas called the circumgalactic medium, or CGM — a reservoir of raw material that stretches 10 to 20 times the size of the visible portion of the galaxy. However, if all the gas within the CGM cooled and collapsed into stars, galaxies would contain far more stars than are actually observed. Something has been holding that process back — and this new research points squarely at the black hole jets.

The team focused on active black holes that emit strong jets — narrow streams of hot, fast-moving plasma shooting out far beyond a galaxy's visible edge. 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. To solve that problem, the researchers got creative with their data.

Combining Two Powerful Telescopes to See the Invisible

The research team combined optical data from the Dark Energy Spectroscopic Instrument survey with radio jet measurements from the LOFAR Two-meter Sky Survey. By stacking DESI spectra with LOFAR radio-jet maps of hundreds of galaxies, they found a strong hydrogen-alpha glow along jet paths — brightest near the galaxy and at the CGM's outer edge — rather than a uniform halo.

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. Unlike the directional glow detected in hydrogen, the magnesium distribution proved isotropic, showing no specific alignment with the radio jets — indicating 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.

Deciding the Fate of Entire Galaxies

By heating, stirring, and disturbing gas throughout the circumgalactic envelope, these powerful plasma streams prevent the raw material from cooling down and falling inward — acting as a brake on star formation, shifting the fate of the host galaxy and potentially making it quiescent over time. In other words, the black hole at a galaxy's core may be the reason some galaxies slowly go dark and stop producing new stars altogether.

"The wider implication is that black holes can shape the lives of galaxies far beyond the small central region where they sit," said Sanchayeeta Borthakur, associate professor at Arizona State University and a co-author of the study. Scientists still do not fully understand how energy from these active black holes reaches such distances and changes along the way, but the team's study provides key evidence as to how this could occur. With next-generation telescopes on the horizon, researchers may soon be able to watch this galaxy-shaping process unfold in real time — and finally answer one of cosmology's most persistent puzzles.