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The fraction of obscured quasars. Junxian Wang Center for Astrophysics University of Science and Technology of China. Collaborated with P. Jiang, Z. Y. Zheng (USTC) and the Chandra Deep Field South team. 2006-10 Xi’an, China. obscured quasar?. Required by the AGN unified model
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The fraction of obscured quasars Junxian Wang Center for Astrophysics University of Science and Technology of China Collaborated with P. Jiang, Z. Y. Zheng (USTC) and the Chandra Deep Field South team 2006-10 Xi’an, China
obscured quasar? • Required by the AGN unified model • Required by the X-ray background model • The population of obscured quasars -- dominate the black hole growth??? • Difficult (rare, hard to select and measure the intrinsic luminosity)
CDFS 202: a classic type 2 quasar Norman et al. 2002 VLT-spectrum Chandra spectrum LX ~ 1045 erg/s NH~ 1024cm-2 narrow high-excitation lines Fe-line @ 6.4 keV 1.4 keV = 6.4/(1+z)
Hard X-ray surveys – better to select obscured quasars • X-ray spectral fitting can give both intrinsic LX and absorption NH
QSO2s Absorption vs luminosity CDFS XMM Lockman Hole From Mainieri et al. (2002)
h r Receding torus? Seyfert QSO
SWIFT/BAT AGN sample14-195 keV selected Markwardt et al. 2005
INTEGRAL IRS AGN sample20-100 keV selectedBassani et al. 2006
Contrary results • Treister et al. 2004 • Eckart et al. 2006 • Dwelly et al. 2005, Dwelly & Page 2006 • Martinez-Sansigre et al. 2005, 2006 (a talk this Saturday) • Zhang 2005
SWIFT/BAT AGN sample14-195 keV selected Markwardt et al. 2005 In the local universe
INTEGRAL IRS AGN sample20-100 keV selectedBassani et al. 2006
We choose 4 -7 keV selected samples in Chandra Deep Fields to study the population of obscured quasars • Why?
Conclusions • More than half of the 4-7 keV selected quasars in Chandra Deep Fields are obscured • Wang et al 2006 ApJ submitted
Conclusions • Redshift incomplete samples in deep fields can produce spurious declination in the fraction of obscured AGN with luminosity
Conclusions • The anti-correlation between absorption and luminosity in the local universe is mainly due to the Compton-thick and radio loud sources