Apr. 22, 2009
Astronomers see active galactic nuclei in a new light
ANN ARBOR, Mich.—Astronomers at the University of Michigan contributed to an international study that gives new insights into the workings of the most energetic known objects in the universe: the jets produced by supermassive black holes at the center of active galaxies.
 | | Image: gamma-ray sky | The study shows that these galactic nuclei emit gamma rays as well as radio waves. Scientists expected this behavior from these nuclei, called blazars. But this is the first time they have been able to confirm it, using data from NASA's Fermi Gamma-ray Space Telescope and from the National Science Foundation's ground-based Very Long Baseline Array radio telescope. Michigan's Radio Astronomy Observatory also provided data about the relative strength of these emissions.
The study will appear in the May 1 edition of Astrophysical Journal Letters.
Hugh Aller, the Ralph B. Baldwin Professor of Astronomy at U-M, and Margo Aller, a research scientist and lecturer in the Department of Astronomy, are among the co-authors.
"For decades at Michigan, we've been studying the outbursts from these extragalactic radio sources in detail," Hugh Aller said. "Fermi found that the strong gamma ray sources are the same ones we had been following.
"The findings help us begin to understand the physical processes going on in these remote active galactic nuclei, which have been very difficult to observe. These objects are a great mystery."
In the center of distant galaxies lurk spinning super massive black holes, which are billions of times heavier than the sun but are confined to a region no larger than our solar system. These rapidly rotating black holes attract stars, gas, and dust, creating huge magnetic fields. The magnetic forces can trap some of the in-falling gas and focus it into narrow jets that flow away from the core of the galaxy at apparent velocities approaching the speed of light.
Astronomers have wondered for decades about the nature and composition of these energetic radio-emitting jets, and if they also radiate in other parts of the electromagnetic spectrum. This is indeed the case, these new findings demonstrate.
"These objects are amazing. Finally we know for sure that the fastest, most compact, and brightest jets that we see with radio telescopes are the ones which are able to kick the light up to the highest energies," said Yuri Kovalev, Humboldt Fellow and scientist at the Max Planck Institute for Radio Astronomy, and first author of the paper.
The Very Long Baseline Array is operated by the National Radio Astronomy Observatory, a facility of the National Science Foundation (NSF). NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership mission, developed in collaboration with the U.S. Department of Energy and important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S. The Michigan Radio Astronomy Observatory is funded by the NSF and by the University of Michigan
The paper is called "The Relation Between AGN Gamma-Ray Emission and Parsec-Scale Radio Jets."
Related Links: Hugh Aller Margo Aller Michigan Radio Astronomy Observatory Max Planck Institute for Radio Astronomy
Contact: Nicole Casal Moore
Phone: (734) 647-1838
Related Categories: Engineering
Related Keywords: galaxies |
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