Unification of Active Galactic Nuclei

  • Elitzur, Moshe (PI)

Grants and Contracts Details


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.
Effective start/end date12/1/1411/30/17


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