Obscured Active Galactic Nuclei and Obscured Accretion
| dc.creator | Fabian, A. C. | |
| dc.date | 2003-04-07 | |
| dc.date.accessioned | 2026-07-07T02:08:11Z | |
| dc.date.available | 2026-07-07T02:08:11Z | |
| dc.description | Most of the local active galactic nucleus (AGN) population is obscured and much of the X-ray background originates in obscured AGNs. The contribution of obscured accretion to the growth of massive black holes is discussed here. The recent identification of significant samples of the X-ray sources that dominate the X-ray background intensity has shown a redshift peak at 0.7-0.8, rather than the redshift of 2 found for bright optical quasars. Obscured accretion has a faster evolution than unobscured accretion. The lower redshift and luminosity of most obscured AGNs mean that although they dominate the absorption-corrected intensity of the X-ray background by a factor of about 3 over unobscured objects, they make only an equal contribution to the local mass density in black holes. Obscured and unobscured AGNs together contribute about 4 x 10^5 Msun/Mpc^3. Type 2 quasars and Compton-thick objects may give another 10^5 Msun/Mpc^3, but no more unless direct determinations from the M-sigma relation seriously underestimate the local black hole mass density, or unless most massive black holes are rapidly spinning (so having a higher radiative efficiency than the 10% assumed above). Obscured accretion probably dominates the growth of black holes with masses below a few times 10^8 Msun, whereas optically bright quasars dominate at higher masses. The luminosity absorbed by the dusty gas in obscured AGNs is reradiated in the mid-infrared and far-infrared bands. The contribution of AGNs drops from about 20% of the mid-infrared background to just a few percent of the far-infrared background. | |
| dc.description | 14 pages, 5 figures to appear in "Carnegie Observatories Astrophysics Series, Vol. 1: Coevolution of Black Holes and Galaxies," ed. L. C. Ho (Cambridge: Cambridge Univ. Press) | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0304122 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0304122 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/5944 | |
| dc.subject | Astrophysics | |
| dc.title | Obscured Active Galactic Nuclei and Obscured Accretion | |
| dc.type | text |