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The fraction of obscured quasars

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

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  1. 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

  2. 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)

  3. 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)

  4. Hard X-ray surveys – better to select obscured quasars • X-ray spectral fitting can give both intrinsic LX and absorption NH

  5. QSO2s Absorption vs luminosity CDFS XMM Lockman Hole From Mainieri et al. (2002)

  6. Ueda et al. 2003

  7. h r Receding torus? Seyfert QSO 

  8. Steffen et al. 2003

  9. SWIFT/BAT AGN sample14-195 keV selected Markwardt et al. 2005

  10. INTEGRAL IRS AGN sample20-100 keV selectedBassani et al. 2006

  11. 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

  12. SWIFT/BAT AGN sample14-195 keV selected Markwardt et al. 2005 In the local universe

  13. INTEGRAL IRS AGN sample20-100 keV selectedBassani et al. 2006

  14. Wang & Jiang 2006

  15. Chandra Deep Fields

  16. We choose 4 -7 keV selected samples in Chandra Deep Fields to study the population of obscured quasars • Why?

  17. Obscured quasars

  18. CDF-S107 4-7 keV selected redshift completeness 100%

  19. CDF-N176 4-7 keV selected, redshift completeness 72%

  20. due to redshift incompleteness?

  21. Conclusions • More than half of the 4-7 keV selected quasars in Chandra Deep Fields are obscured • Wang et al 2006 ApJ submitted

  22. Conclusions • Redshift incomplete samples in deep fields can produce spurious declination in the fraction of obscured AGN with luminosity

  23. Conclusions • The anti-correlation between absorption and luminosity in the local universe is mainly due to the Compton-thick and radio loud sources

  24. Thank you!

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