**full Title** Asp Conference Series, Vol. **volume**, **year of Publication** **names of Editors** High-redshift Obscured Quasars
نویسنده
چکیده
Using mid-infrared and radio criteria, we select a sample of candidate z ∼ 2 obscured quasars. Optical spectroscopy confirms about half of these as type-2 quasars, and modelling the population suggests 50-80% of the quasars are obscured. We find some flat radio spectrum type-2 quasars, and tentative evidence for obscuration unrelated to the torus. Using a similar sample, we also find evidence for a significant fraction of Compton-thick quasars.
منابع مشابه
**title** Asp Conference Series, Vol. **volume**, **publication Year** **editors** Obscured Accretion and Black Holes
The evidence for obscured AGN and in particular for obscured quasars is discussed. The spectrum and source modelling of the X-ray Background suggests that most massive black holes grow by obscured accretion. A possible major growth phase which is Compton thick is explored and shown to be difficult to detect directly with current instruments .
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This is a summary of the 'Astronomy Perspective' of the 4th meeting on Statistical Challenges in Modern Astronomy held at Penn State University in June 2006. We comment on trends in the Astronomy community towards Bayesian methods and model selection criteria. We describe two examples where Bayesian methods have improved our inference: (i) photometric redshift estimation (ii) orbital parameters...
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The properties of radio loud active galaxies (radiogalaxies, BL Lac objects and radio loud quasar) at low and high redshift are briefly reviewed and compared. The recently derived empirical relations between central black hole mass and host properties allow one to explore the demographics of massive black hole in active galaxies. It is shown that all classes of active galaxies considered exhibi...
متن کامل**title** Asp Conference Series, Vol. **volume**, **publication Year** **editors** Wfcam, Ukidss, and Z = 7 Quasars
We estimate the number of z ≃ 7 quasars that will be discovered in the Large Area Survey (LAS) element of the UKIRT Infrared Deep Sky Survey (UKIDSS). The LAS will cover 4000 sq degs of the northern sky to K = 18.4, which is 3 mag. deeper than 2MASS. The Sloan Digital Sky Survey has extended the quasar redshift limit to z = 6.3. We demonstrate that to reach higher redshifts z ∼ 7, when Lyα has ...
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