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Most supermassive black hole growth is obscured by dust

By SpaceRef Editor
August 15, 2005
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Astrophysics, abstract

From: Alejo Mart\’inez-Sansigre [view email]
Date: Tue, 24 May 2005 09:14:07 GMT (61kb)

Most supermassive black hole growth is obscured by dust

Alejo Martinez-Sansigre,
Steve Rawlings,
Mark Lacy,
Dario Fadda,
Francine R. Marleau,
Chris Simpson,
Chris J. Willott,
Matt J. Jarvis

Comments: To appear in Nature. Supplementary Information can be found at
this http URL

Supermassive black holes underwent periods of exponential growth which are
observed as quasars in the distant Universe. The summed emission from these
quasars generates the cosmic X-ray background, the spectrum of which has been
used to argue that most black-hole growth is obscured. There are clear examples
of obscured black-hole growth in the form of `Type-2′ quasars, but their
numbers are fewer than expected from modelling of the X-ray background. Here we
report on the direct detection of a population of distant `Type-2′ quasars
which is at least comparable in size to the well-known unobscured Type-1
population. This population was found by selecting objects whose mid-infrared
and radio emissions are characteristic of quasars, but which are faint at
near-infrared and optical wavelengths. This population is responsible for most
of the black hole growth in the young Universe and, throughout cosmic history,
black-hole growth occurs in the dusty, gas-rich centres of active galaxies.

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