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IR Reveals Evidence of Galactic Collisions

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COLUMBUS, Ohio, April 29 -- Astronomers from Ohio State University used infrared telescopes to discover that collisions and near-collisions between spiral galaxies are more common than had been suspected. Professor Jay Frogel and Paul Eskridge, a postdoctoral research fellow, have spent the last five years compiling pictures of more than 200 nearly spiral galaxies in a search for those with the distinctive barred spiral shape. Scientists believe that the bar-shaped bands of stars at the center of barred spiral galaxies form when two galaxies collide or have a near miss as they drift through space. Traditional optical telescopes found about 30 percent of the 200 galaxies studied to be barred spiral; however, the fraction of strongly barred galaxies was found to be approximately twice as high when viewed through infrared (IR) telescopes.
Frogel and Eskridge used the Ohio State InfraRed Imager and Spectrometer (OSIRIS), designed and built at the University, to penetrate the dust at the center of spiral galaxies. IR cameras such as OSIRIS also allow astronomers to observe older, cooler stars that radiate most of their energy at IR wavelengths. Such stars can make up as much as 90 percent of a galaxy's matter; many of the stars in the bars of barred spirals are older and thus not visible through traditional telescopes. By comparing the visible or optical view of a galaxy to the IR view, scientists may be able to determine when the stars in a galaxy formed and thus how the galaxy evolved.
The researchers presented their findings at a recent meeting of the American Astronomical Society in Austin, Texas. They hope to distribute the photos on CD-ROM through NASA, and believe that the IR data collected may help NASA to plan future space-based observing missions.
Apr 1999
News & Featuresspectroscopy

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