tokens: by observations of polarised optical radiation. However, polarization signatures are only detected in a limited number of sources, and at present there is no compelling evidence for a simple obscuring torus geometry, possibly suggesting a more complex picture (see the recent review by Netzer 2015 , and references therein). The different AGN obscuration models discussed so far may be broadly divided into two categories: static and dynamical. For instance, analytic calculations suggest that the vertical support for a geometrically thick obscuring torus can be provided by infrared radiation pressure (Krolik 2007 ). The different nature of smooth and clumpy dust tori in different AGN luminosity regimes has been analysed by Hönig Beckert ( 2007 ). Circulation of gas leading to the development of radiation-driven ‘fountains’ has also been proposed as a possible mechanism for the formation of the obscuring torus (Wada 2012 ). The detailed evolution of dusty gas clouds illuminated by the central AGN has been followed through 3D radiation hydrodynamic (RHD) simulations (Namekata, Umemura Hasegawa 2014 ); while the dynamics of dusty gas subject to anisotropic disc emission, X-ray heating, and reprocessed IR radiation, has also been analysed via axisymmetric RHD simulations (Namekata Umemura 2016 ). Another class of models consider the obscuring toroidal structure as supported by winds driven by IR radiation pressure, due to the relatively high opacity of dust in the infrared (Dorodnitsyn, Bisnovatyi-Kogan Kallman 2011 ). A further refinement of the model based on multi-dimensional RHD simulations confirms that the geometrically thick obscuration on pc-scales can indeed be provided by outflows driven by IR radiation pressure on dust (Dorodnitsyn, Kallman Bisnovatyi-Kogan 2012 ). On the other hand, 3D time-dependent RHD simulations of dusty tori suggest that UV radiation pressure on dust can drive powerful winds with considerable mass loss rates (Chan Krolik 2016 ). The most recent multidimensional simulations of dusty gas acceleration in star-forming galaxies suggest that dusty clouds are able to survive longer when accelerated by radiation pressure rather than entrained in a hot outflow (Zhang et al. 2018 ). Here, we envisage a simple picture in which AGN radiative feedback, driven by radiation pressure on dust, strongly affects the distribution of dusty gas in the host galaxy. We assume a spherical shell geometry throughout the paper, while we separately discuss the case of anisotropic emission from the accretion disc in Section 5 . Our results are in agreement with the observational data based on the 70 month Swift /BAT AGN catalogue, which is the most complete sample of X-ray selected AGNs, with measured N H and λ values, currently available. This suggests that our model assumptions are reasonable and sufficient for the purpose of comparison with X-ray observations. In summary, the overall picture is entirely consistent with AGN radiation pressure
ner_tags: O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O B-Citation I-Citation O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation O O O O O O O O O O O O O O O O O B-Model I-Model I-Model B-Model O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O B-Wavelength O O O B-Wavelength O O O O O O O B-Model I-Model B-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O B-Wavelength B-Citation I-Citation I-Citation I-Citation O O O O O O O O O B-Model I-Model I-Model O O O O O O O O O O O O O O O O B-Wavelength O O O O B-Citation I-Citation I-Citation I-Citation O O O O O B-Model I-Model I-Model I-Model O O O O O B-Wavelength O O O O O O O O O O O O O B-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Dataset I-Dataset I-Dataset I-Dataset I-Dataset I-Dataset O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O