Grants and Contracts Details
Description
The inevitable spread in properties of the toroidal obscuration of active galactic nuclei (AGNs)
invalidates the widespread notion that type 1 and 2 AGNs are intrinsically the same objects, drawn randomly from the distribution of torus
covering factors. Instead, AGNs are drawn preferentially from this distribution; type 2 are more
likely drawn from the distribution higher end, type 1 from its lower end. Meaningful studies of
unification statistics cannot be conducted without first determining the intrinsic distribution
function of torus covering factors, which has never been determined. A reliable determination of
this distribution function requires IR modeling of an unbiased, complete sample of AGNs, and the
only practical method to select AGNs with minimal classification bias is through hard X-ray
surveys; although such selection still misses the most heavily obscured, Compton thick AGNs, it is
the least biased method of AGN selection. We will match the INTEGRAL, Swift-BAT and XMM-Newton
X-ray archives with the infrared Spitzer archive for a blindly selected sample of AGNs for
extensive modeling in which the SED of every source is matched against our entire database
of clumpy torus models (currently more than 1.2 million) for the best fit. Using Bayesian inference
analysis we will determine the confidence in the parameters derived for every modeled SED. For each
source in the sample we will determine the torus covering factor from the fitted parameters of the
dusty cloud distribution, and construct for the entire sample the probability distribution
function of covering factors, including error estimate.
Status | Finished |
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Effective start/end date | 12/1/14 → 11/30/17 |
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