On the detectability of distant Compton-thick obscured quasars
Abstract
Chandra and XMM-Newton have resolved the 2-8keV X-ray background (XRB) into point sources. Many of the fainter sources are obscured active galactic nuclei (AGN) with column densities in the range of 1022-1023cm-2, some of which have quasar-like luminosities. According to obscuration models, the XRB above 8keV is dominated by emission from Compton-thick AGN, with column densities exceeding 1.5×1024cm-2. Here, we consider whether Compton-thick quasars are detectable by Chandra and XMM-Newton by their direct (i.e. not scattered) X-ray emission. Detectability is optimized if the objects individually have a high luminosity and high redshift, so that the direct emission has a significant flux in the observed band. Using a simple galaxy formation model incorporating accreting black holes, in which quasars build most of their mass in a Compton-thick manner before expelling the obscuring matter, we predict that moderately deep 100-ks Chandra and XMM-Newton exposures may contain a handful of detectable Compton-thick quasars. Deep Ms or more Chandra images should contain 50-100 distant, optically faint, Compton-thick sources. In passing we show that radiation pressure can be as effective in expelling the obscuring gas as quasars winds, and yields a black hole mass proportional to the velocity dispersion of the host bulge to the fourth power.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2002
- DOI:
- 10.1046/j.1365-8711.2002.05138.x
- arXiv:
- arXiv:astro-ph/0111422
- Bibcode:
- 2002MNRAS.329L..18F
- Keywords:
-
- GALAXIES: ACTIVE;
- QUASARS: GENERAL;
- GALAXIES: SEYFERT;
- INFRARED: GALAXIES;
- X-RAYS: GENERAL;
- Astrophysics
- E-Print:
- 5 pages, accepted for publication in MNRAS