Tight Arms Linked to Bigger Black Holes in Galaxies

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And if the interaction fuels the combined galaxy's supermassive black hole, it can produce a halo of matter called a quasar.

The quasar will blow out debris, clearing a view to the newborn stars. But often by that time the stars have become too faint to outshine the powerful quasar.

Brotherton and his team found an object in the late 1990s that possessed the spectral signatures of both a quasar and an older starburst.

Hubble captured images of the rare object and showed that it was the remnant of a galaxy merger.

The researchers have since used Hubble to follow up on 29 candidate quasars identified by the Sloan Digital Sky Survey.

"The images started coming in, and we were blown away," Brotherton said.

"We see not only merger remnants … but also post-starburst quasars with interacting companion galaxies, double nuclei, starbursting rings, and all sorts of messy structures."

(Related pictures: "'Toothbrush,' 'Firefly' Among Galactic Smashups" [April 24, 2008].)

Star Lab

Conference presenter Médéric Boquien, an astronomer at the University of Massachusetts, added that debris from galaxy collisions can be used as a laboratory to study the process of star formation.

Boquien's team has been using the Spitzer Space Telescope, Galaxy Evolution Explorer, and eight ground-based telescope to peer at six interacting galaxy systems.

All of the systems are within 375 million light-years of Earth.

In each of the interacting galaxies, up to 85 percent of star formation takes place in the collision debris between galaxies instead of inside the parent galaxies themselves.

"The best regions to study star formation would be those completely devoid of old stars, and we were able to find some regions which satisfy this criteria," Boquien said.

Such areas are generally quite isolated, unlike the star-forming regions inside galaxies, which can be surrounded by many bright astronomical objects.

"As star formation apparently occurs in a similar way in galaxies, results we obtain studying intergalactic star-forming regions can be confidently extended to galaxies."

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