Investigating AGN Tori through X-ray and Infrared Observations

Date: 
Tuesday, January 17, 2017 - 3:30pm PST
Speaker: 
Kohei Ichikawa
Affiliation: 
UTSA/Columbia University
Location: 
N232, room 103
Event Type: 
Seminar

X-ray and mid-infrared (MIR) wavelength observations are crucial for studies of active galactic nuclei (AGN) because X-rays trace the intrinsic power of AGN and the MIR traces the warm (T~200-300 K) thermal dust (called ``torus'') surrounding the central engine. However, the geometrical structure of the torus is not well understood due to its compact size (r<10 pc).  In this talk, I will first introduce our recently published infrared catalog of Swift/BAT hard X-ray 70 month AGN catalog. Using this complete IR/X-ray data set, I will show that the mid-IR emission of AGN is almost isotropic, indicating that AGN torus is preferable to be made of clumps, which is easy for us to look into the central engine even in the edge-on view (Ichikawa et al. 2012; 2016b). Next, I will show how those clumpy tori can explain the spectral energy distribution of AGN in the mid-IR bands (Ichikawa et al. 2015).  If time allows, I will also introduce a "dying" AGN who was active ~105 yr ago but whose AGN activity seems to be quiet now (Ichikawa et al. 2016a).

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