the fraction of obscured quasars
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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The fraction of obscured quasars
Junxian Wang
Center for AstrophysicsUniversity of Science and Technology of China
2006-10 Xi’an, China
Collaborated with P. Jiang, Z. Y. Zheng (USTC)
and the Chandra Deep Field South team
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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)
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CDFS 202: a classic type 2 quasar
LX ~ 1045 erg/s NH ~ 1024cm-2
narrow high-excitation lines Fe-line @ 6.4 keV
VLT-spectrum Chandra spectrum
Norman et al. 2002
1.4 keV = 6.4/(1+z)
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• Hard X-ray surveys – better to select obscured quasars
• X-ray spectral fitting can give both intrinsic LX and absorption NH
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Absorption vs luminosity
QSO2s
From Mainieri et al. (2002)
CDFS XMM Lockman Hole
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Ueda et al. 2003
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Receding torus?
Seyfert QSO
h
r
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Steffen et al. 2003
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SWIFT/BAT AGN sample
14-195 keV selected
Markwardt et al. 2005
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INTEGRAL IRS AGN sample20-100 keV selectedBassani et al. 2006
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• 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
Contrary results
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SWIFT/BAT AGN sample
14-195 keV selected
Markwardt et al. 2005
In the local universe
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INTEGRAL IRS AGN sample20-100 keV selectedBassani et al. 2006
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Wang & Jiang 2006
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Chandra Deep Fields
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• We choose 4 -7 keV selected samples in Chandra Deep Fields to study the population of obscured quasars
• Why?
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Obscured quasars
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CDF-S107 4-7 keV selected redshift completeness 10
0%
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CDF-N176 4-7 keV selected, redshift completeness 72%
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due to redshift incompleteness?
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Conclusions
• More than half of the 4-7 keV selected quasars in Chandra Deep Fields are obscured
• Wang et al 2006 ApJ submitted
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Conclusions
• Redshift incomplete samples in deep fields can produce spurious declination in the fraction of obscured AGN with luminosity
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Conclusions
• The anti-correlation between absorption and luminosity in the local universe is mainly due to the Compton-thick and radio loud sources
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Thank you!