Where are the supermassive black holes hiding?

26 July 2006

ESA Press Release

Source Link

This artist's impression shows the thick dust torus that astronomers believe surrounds many supermassive black holes and their accretion discs. When the torus is seen edge-on as in this case, much of the light emitted by the accretion disc is blocked, creating a "hidden" black hole.

However, the sharp gamma-ray and X-ray eyes of Integral can peer through the thick dust and identify the black hole within. An Integral survey of the local universe found few hidden black holes, implying that they must have existed earlier (deeper) in the universe.

Credits: ESA / V. Beckmann (NASA-GSFC)

____________________________________________________________________

European and American scientists, on a quest to find super-massive black holes hiding in nearby galaxies, have found surprisingly few. Either the black holes are better hidden than scientists realised or they are lurking only in the more distant universe.

Scientists are convinced that some super-massive black holes must be hiding behind thick clouds of dust. These dusty shrouds allow only the highest energy X-rays to shine through. Once in space, the X-rays combine into a cosmic background of X-rays that permeates the whole of space.

The search for hidden black holes is part of the first census of the highest-energy part of the X-ray sky. Led by Loredana Bassani, IASF, Italy, a team of astronomers published results in The Astrophysical Journal Letters in January this year. They show the fraction of hidden black holes in the nearby Universe to be around 15 percent, using data from ESA