The narrow Fe K$α$ line and the molecular torus in active galactic nuclei - an IR/X-ray view

Claudio Ricci; Yoshihiro Ueda; Kohei Ichikawa; Stephane Paltani; Rozenn Boissay; Poshak Gandhi; Marko Stalevski; Hisamitsu Awaki

doi:10.1051/0004-6361/201322701

paper

The narrow Fe K $α$ line and the molecular torus in active galactic nuclei - an IR/X-ray view

arXiv:1405.2645 · doi:10.1051/0004-6361/201322701

Abstract

The narrow component of the iron K $α$ 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 $α$ equivalent width (EW) and the physical properties of the torus. In a recent work we have shown that the decrease of the covering factor of the torus with the luminosity, as expected by luminosity-dependent unification models, would be able to explain the decrease of Fe K $α$ 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 $α$ line. We correct the values of the Fe K $α$ EW 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 Fe K $α$ EW and $f_{obs}$ shows a slope that is consistent with the expected value, albeit with a low statistical significance. A trend that is consistent with the theoretical prediction is also found when comparing the Fe K $α$ EW to $N_{H}^{T}$ . Our work seems to confirm that the bulk of the narrow Fe K $α$ line is produced by the same material responsible for the MIR emission.

arXiv commentA&A in press, 15 pages, 5 Figures, 3 tables - Few references updated

The narrow Fe K $α$ line and the molecular torus in active galactic nuclei - an IR/X-ray view

Abstract

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Cited by in corpus (35)

The narrow Fe Kα line and the molecular torus in active galactic nuclei - an IR/X-ray view

Abstract

References in corpus (70)

Cited by in corpus (35)

The narrow Fe K $α$ line and the molecular torus in active galactic nuclei - an IR/X-ray view