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The obscuration by dust of most of the growth of supermassive black holes

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

Supermassive black holes underwent periods of exponential growth during which we seem them 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. We selected objects that have mid-infrared and radio emissions 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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Alejo Martinez-Sansigre, Steve Rawlings, Mark Lacy, Dario Fadda, Francine R. Marleau, Chris Simpson, Chris J. Willott, Matt J. Jarvis. 2005-07-29. The obscuration by dust of most of the growth of supermassive black holes. https://doi.org/10.1038/nature03829

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