April 23, 2009

Astronomers study galaxy’s gamma rays

An international team of astronomers has used a U.S. radio telescope to study the brightest galaxies that the Fermi Gamma-ray Space Telescope can see.

Yuri Kovalev at the Max Planck Institute for Radio Astronomy in Germany said the study solidifies the link between an active galaxy's gamma-ray emissions and its powerful radio-emitting jets.

Kovalev and colleagues used the world's largest radio telescope -- the National Science Foundation's Very Long Baseline Array -- a set of 10 radio telescopes located from Hawaii to St. Croix in the U.S. Virgin Islands and operated by the National Radio Astronomy Observatory. When the signals from these telescopes are combined, the array acts as a single enormous radio dish more than 5,300 miles across, resolving details about a million times smaller than Fermi can and 50 times smaller than any optical telescope.

For more than a decade, we have collected images of the brightest galaxies in the radio sky to study the changing structures of their jets, said Purdue University Professor Matthew Lister, a member of the research team. We've waited a long time to compare our measurements with the findings in the gamma-ray sky -- and now, thanks to this state-of-the-art space observatory, we finally can.

The team's findings appear in two papers to be published in the May 1 issue of The Astrophysical Journal Letters.