Supermassive Black Hole Jets Light Up Galactic Halos, Potentially Halting Star Formation
Astronomers have found that narrow jets from supermassive black holes ionize gas far beyond their host galaxies, creating bright H-alpha trails that may keep the surrounding gas hot and suppress future star formation.
Researchers examined active galaxies with powerful radio jets using combined optical data from DESI and radio maps from the LOFAR Two-meter Sky Survey. By stacking signals from many objects, they uncovered a pronounced H-alpha glow aligned with the jet direction, while the average signal elsewhere remained weak. The bright spots occur both near the galaxy and near the outer edge of the circumgalactic medium, showing that jets deposit energy over hundreds of thousands of light-years.
Complementary magnesium absorption measurements revealed a more uniform cool-gas reservoir, underscoring that the jets specifically heat and ionize gas along their paths. The authors argue that this heating prevents the gas from cooling and collapsing into new stars, effectively acting as a brake on galaxy growth. Their paper appears in the Astrophysical Journal Letters and is supported by NASA, STScI, and NSF.
