2006/03/30 by Jian-Min Wang, Yan-Mei Chen, Luis C. Ho +1 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Binary black hole #Black hole (networking) #Galaxies: Formation, Evolution, Phenomena #Intermediate-mass black hole #Quasar #Radiative transfer #Redshift #Spin-flip #Supermassive black hole #astro-ph
paper · pdf · doi:10.1086/504842
published as Astrophys.J.642:L111-L114,2006 · 4 page in emulate5.sty, 3 figures. accepted by ApJL
arxiv created 2006/03/30 · openalex publication_date 2006/04/25 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
It has long been believed that accretion onto supermassive black holes powers quasars, but there are still relatively few observational constraints on the spins of the black holes. We address this problem by estimating the average radiative efficiencies of a large sample of quasars selected from the Sloan Digital Sky Survey, by combining their luminosity function and their black hole mass function. Over the redshift interval 0.4 < z < 2.1, we find that quasars have average radiative efficiencies of ~30%-35%, strongly suggesting that their black holes are rotating very rapidly, with specific angular momentum a ≈ 1, a value that remains roughly constant with redshift. The average radiative efficiency could be reduced by a factor of ~2, depending on the adopted zero point for the black hole mass scale. The inferred large spins and their lack of significant evolution are in agreement with the predictions of recent semianalytical models of hierarchical galaxy formation if black holes gain most of their mass through accretion.