Abstract

The narrow component of the iron K alpha is an almost ubiquitous feature in the X-ray spectra of active galactic nuclei (AGN) and is believed to originate in neutral material, possibly located in the molecular torus. This would imply a tight connection between the Fe K alpha equivalent width (EW) and the physical properties of the torus. In a recent work we have shown that the decrease in the covering factor of the torus with the luminosity, as expected by luminosity-dependent unification models, would be able to explain the decrease in be K alpha EW with the luminosity (i.e. the X-ray Baldwin effect). Recent developments in the study of the mid-IR (MIR) spectrum of AGN allow important parameters of the torus to be deduced, such as its covering factor (f(obs)) and equatorial column density (N-H(T)). by applying clumpy torus models. Using XMM-Newton/EPIC observations of a sample of 24 type-I AGN, we investigate the relation between the physical parameters of the torus obtained by recent MIR works and the properties of the Fe K alpha line. We correct the values of the Fe K alpha LW by taking the inclination angle, the photon index, the equatorial column density, and half opening angle of the torus into account using a physical torus model of X-ray reprocessed radiation. We find that the relation between be K alpha LW and f(obs) shows a slope that is consistent with the expected value, albeit with low statistical significance. A trend that is consistent with the theoretical prediction is also found when comparing the Fe K alpha LW to N. Our work seems to confirm that the bulk of the narrow Fe K alpha line is produced by the same material responsible for the MIR emission.