RGS Quasar Spectrum
Credit: M. Sako (Columbia)

X-raying the Warm Absorber

The centers of active galaxies are thought to host extremely massive black holes. These central black holes, which can hold the equivalent of mass of a million suns, produce very violent explosions of X-rays which make the active galaxies bright and very variable. Apparently nature tries to shield the mysteries of the central black holes from prying eyes by placing a screen of absorbing material between us and the black hole. This material, sometimes called the "warm absorber" itself produces characteristic emission of radiation. It also absorbs the X-rays produced by the central black hole, and this absorption effect can be used to study both the nature of the absorber and the black hole itself. The XMM-Newton X-ray telescope has provided a good look at the absorption of radiation produced by the warm absorber in the quasar IRAS 13349+2438. The graph above shows the X-ray spectrum produced by the black hole in this quasar. At certain characteristic energies the X-ray emission drops suddenly; these "absorption lines" are produced as X-rays from the black hole are swallowed up by certain atoms (like carbon, nitrogen, and iron) in the warm absorbing material between us and the black hole.

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Page Author: Dr. Michael F. Corcoran
Last modified April 4, 2002