Radiative transfer modelling of parsec-scale dusty warped discs

Abstract

Warped discs have been found on (sub-)parsec scale in some nearby Seyfert nuclei, identified by their maser emission. Using dust radiative transfer simulations we explore their observational signatures in the infrared in order to find out whether they can partly replace the molecular torus. Strong variations of the brightness distributions are found, depending on the orientation of the warp with respect to the line of sight. Whereas images at short wavelengths typically show a disc-like and a point source component, the warp itself only becomes visible at far-infrared wavelengths. A similar variety is visible in the shapes of the spectral energy distributions. Especially for close to edge-on views, the models show silicate feature strengths ranging from deep absorption to strong emission for variations of the lines of sight towards the warp. To test the applicability of our model, we use the case of the Circinus galaxy, where infrared interferometry has revealed a highly elongated emission component matching a warped maser disc in orientation and size. Our model is for the first time able to present a physical explanation for the observed dust morphology as coming from the AGN heated dust. As opposed to available torus models, a warped disc morphology produces a variety of silicate feature shapes for grazing lines of sight, close to an edge-on view. This could be an attractive alternative to a claimed change of the dust composition for the case of the nearby Seyfert 2 galaxy NGC 1068, which harbours a warped maser disc as well.

accepted by MNRAS

References in corpus (8)

• Resolving the complex structure of the dust torus in the active nucleus of the Circinus galaxy
• Radiative Transfer Modeling of Three-Dimensional Clumpy AGN Tori and its Application to NGC 1068
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• Resolving the obscuring torus in NGC 1068 with the power of infrared interferometry: Revealing the inner funnel of dust
• Multi-phase Nature of a Radiation-Driven Fountain with Nuclear Starburst in a Low-mass Active Galactic Nucleus
• The effect of stellar feedback on the formation and evolution of gas and dust tori in AGN
• The Parsec-scale Accretion Disk in NGC 3393
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Cited by in corpus (4)

• Active Galactic Nuclei: what's in a name?
• Physically motivated X-ray obscurer models
• The life cycle of starbursting circumnuclear gas discs
• Polarized radiative transfer modeling of warped and clumpy dusty tori