Massive Black Holes May Halt New Star Creation in Mature Galaxies

Massive black holes may just be blocking the formation of new stars in aging galaxies. Scientists have found that the radio-frequency-emitting particles that the black holes spew out can halt the creation of stars.

"When you look into the past history of the universe, you see these galaxies building stars," said Tobias Marriage, co-lead author of the new study, in a news release. "At some point, they stop forming stars and the question is: Why? Basically these active black holes give a reason for why stars stop forming in the universe."

In this case, the researchers found that the Sunyaev-Zel'dovich effect signature, usually called the SZ effect, can be used to learn a great deal about smaller galaxy formation. The SZ effect occurs when high-energy electrons in hot gas interact with faint light in the cosmic microwave background, light left over from earliest times when the universe was a thousand times hotter and a billion times denser than today.

"What we're doing is asking a different question than what has been previously asked," said Megan Gralla, one of the researchers. "We're using a technique that's been around for some time and that researchers have been very successful with, and we're using it to answer a totally different question in a totally different subfield of astronomy."

In space, hot gas that's drawn into a galaxy can cool down, condense and form stars. In this case, though, the scientists found that elliptical galaxies, or mature galaxies, with radio-frequency feedback all contain hot gas and a dearth of infant stars. This, in particular, provided credence to the theory that radio-frequency feedback is the "off switch" for star-making in mature galaxies.

That said, it's still not known why black holes in mature galaxies begin to emit radio-frequency feedback. What the findings do show, though, is why exactly stars stop forming in mature galaxies. This, in particular, shows a bit more bout galaxy evolution.

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.