[SEMINARI] Reminder: Ricci's talk today on Unification Scenarios of AGN at X-ray, at 12:00

[Eduardo Ros]

Dear all,

let me remind you about the seminar today at noon.

See you there!

Eduardo

http://celeste.uv.es/daa/seminari.php.UTF8?id=1055

Unification scenarios of Active Galactic Nuclei: an X-ray view

Claudio Ricci

ISDC - Science data center for Astrophysics, University of Geneva,  
Switzerland

Seminari del departament d'Astronomia i Astrofísica

Wednesday, May 23th, 2012

12:00

Summary

Active Galactic Nuclei (AGN) are the most luminous persistent sources  
of radiation in the Universe. The unified model of AGN foresees that  
different types of AGN are intrinsically the same object, and that  
observational differences are solely due to different inclination  
angles with respect to an obscuring toroidal structure. However,  
recent results have shown that the anisotropic absorber appear to be  
clumpy and to have covering factors inversely proportional to the  
luminosity.  The hard X-rays (>10 keV) are a very suitable energy band  
for studying the unified model. Absorption does not play an important  
role at these energies, allowing to have a direct look at the central  
engine of the AGN. By analyzing the INTEGRAL IBIS/ISGRI average hard X- 
ray (17-250 keV) spectra of ~200 radio-quiet local AGN, we recently  
found that more obscured AGN have a larger reflection component than  
less obscured ones, which cannot be easily explained by the unified  
model, but might require an intrinsic difference in the covering  
factor of the torus between different types of AGN. In my talk, I will  
present several unification scenarios, and discuss their possible  
relation with the observed decrease of the equivalent width of the  
iron Kalpha line with the luminosity (i.e. the X-ray Baldwin effect). 
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