Resolving AGN tori in the mid-infrared: a new unbiased probe of intrinsic accretion power

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• Poshak Gandhi, Riken
• Wednesday 16 September 2009, 10:45-11:00
• Sackler Lecture Theatre, IoA.

If you have a question about this talk, please contact Alexander Blustin.

We show that resolved mid-infrared (mid-IR) imaging of active galactic nuclei (AGN) is an isotropic probe of their intrinsic luminosities. We have obtained the largest sample to date of 8-m telescope diffraction-limited mid-IR imaging of radio-quiet AGN (42 sources so far), using which we find a strong correlation between mid-IR (12 micron) and intrinsic X-ray (2-10 keV) luminosities. The relation holds true for Seyferts of all types, including unobscured, obscured, as well as heavily Compton-thick sources. Thus, the mid-IR directly probes the intrinsic accretion power irrespective of obscuration, and provides a new and accurate proxy of AGN luminosity (complementing other tools such as the forbidden [OIII]5007 emission line). The relation may also be extended smoothly to the higher luminosity quasar regime. Most star formation around the nuclei is resolved out, and the remaining unresolved mid-IR flux is dominated by the AGN alone. This enables clean estimates of bolometric luminosities to be derived for the first time. The dispersion in the mid-IR:X-ray relation is tight enough to provide sensitive discrimination between physical models of clumpy vs. smooth dusty tori geometries. In addition, our relation also provides a simple pathway for estimating the intrinsic powers of Compton-thick AGN .

This talk is part of the New Results in X-ray Astronomy 2009 series.

This talk is included in these lists:

• Combined External Astrophysics Talks DAMTP
• Cosmology, Astrophysics and General Relativity
• Institute of Astronomy One-day Meetings
• Institute of Astronomy Talk Lists
• New Results in X-ray Astronomy 2009
• Sackler Lecture Theatre, IoA

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