A study led by astronomers at Arizona State University and the Raman Research Institute provides evidence that jets emitted by supermassive black holes at galactic centers can affect the cosmic gas reservoirs surrounding galaxies. These findings may explain a long-standing astronomical puzzle regarding why galaxies do not produce more stars despite being surrounded by abundant star-forming material.
Galaxies are enveloped by a region called the circumgalactic medium, or CGM, which extends roughly 10 to 20 times farther than the visible galaxy itself. This reservoir contains cold, dense gas that can cool, accumulate, and eventually form new stars. However, astronomers have observed that much of this available gas does not convert into stars as models would predict. The new research suggests that jets of extremely hot plasma launched by supermassive black holes may disturb this gas reservoir, potentially preventing significant portions from cooling and falling inward to form new stars.
The researchers analyzed data from hundreds of active galaxies, combining observations from the Dark Energy Spectroscopic Instrument survey with radio measurements from the LOFAR Two-meter Sky Survey. They searched for ionized hydrogen emissions along the paths of black hole jets. The team found that while the ionized hydrogen signal was weak when measurements from all directions were averaged, the signal became significantly stronger along the radio jets themselves. This pattern indicates that the jets create a concentrated, directional effect rather than uniformly illuminating surrounding gas.
The study identified two regions of particularly bright ionized hydrogen emissions: one near the galaxy where the jet first encounters the CGM, and another far from the galaxy near the outer edge of the reservoir. These findings reveal how jets can alter gas conditions across distances of hundreds of thousands of light-years from a galactic center. By heating and ionizing gas along their paths, the jets may influence whether galaxies continue producing stars or become inactive. The research was published in the Astrophysical Journal Letters and suggests that despite their small size relative to galaxies, supermassive black holes can exert significant influence over galactic evolution and development.
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