Astronomers at U-M 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 super-massive black holes at the center of active galaxies.
The study shows 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 is in the May 1 edition of Astrophysical Journal Letters.
Hugh Aller, the Ralph B. Baldwin Professor of Astronomy, 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 says. “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,” says Yuri Kovalev, Humboldt Fellow and scientist at the Max Planck Institute for Radio Astronomy, and first author of the paper.
