2005/05/31 by Alejo Martínez‐Sansigre, Alejo Martinez-Sansigre, Steve Rawlings +9 · 3 citations
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Black hole (networking) #COSMIC cancer database #Demography #Galaxies: Formation, Evolution, Phenomena #Galaxy #Intermediate-mass black hole #Physics #Population #Quasar #Supermassive black hole #astro-ph
paper · pdf · doi:10.1038/nature03829
published as Nature 436:666-669,2005 · 10 pages, 2 figures, to appear in Nature on 4th August. Title and opening paragraph modified to Nature house style. Minor rearrangement and correction to table 1. Supplementary Information can be found at http://www-astro.physics.ox.ac.uk/~ams/
arxiv created 2005/07/29 · openalex publication_date 2005/08/01 · arxiv updated 2014/10/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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.