Evidence of galactic 'cannibalism' studied

CHARLOTTESVILLE, Va., June 25 (UPI) -- U.S. and Taiwanese astronomers say they've used radio-telescope images to reveal suspected, but previously unseen, "galactic cannibalism" by black holes.

The scientists said it's been long suspected that gigantic black holes at the center of some spiral galaxies, called Seyfert galaxies, consume galactic material.

One leading theory posited Seyfert galaxies are disturbed by close encounters with neighboring galaxies, thus stirring up their gas and bringing more of it within the gravitational reach of the black hole.

Now, images of hydrogen gas in Seyferts made using the National Science Foundation's Very Large Array, or VLA, radio telescope have confirmed the majority are, in fact, disturbed by encounters with neighbor galaxies.

"The VLA lifted the veil on what's really happening with these galaxies," said Cheng-Yu Kuo, a graduate student at the University of Virginia. "Looking at the gas in these galaxies clearly showed that they are snacking on their neighbors. This is a dramatic contrast with their appearance in visible starlight."

Kuo, Paul Ho of Harvard University, along with Ya-Wen Tang and Jeremy Lim of the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan, report their findings in the Astrophysical Journal.