1 Introduction

In the unified models of active galactic nuclei (AGN), the observed differences between various types of AGN are explained in terms of collimated radiation, obscuration and viewing angle effects on intrinsically similar objects (e.g. Antonucci 1993). Specifically for Seyfert galaxies, there is increasing evidence (for references see Sect. 4 and Kotilainen & Ward 1997; hereafter KW97), that in Seyfert 2s optically thick material, in the form of a thick disk or a dusty torus, blocks our direct view of the compact nucleus and the broad line region (BLR), and collimates the ionising photons along the minor axis of the torus into two oppositely directed cones.

The emphasis in studies of the nuclear regions of Seyferts has been on the emission line properties (e.g. integral field spectroscopy and emission line imaging). However, although the nuclear torus is expected to be too small to be resolved, its outer parts, e.g. in the form of a flattened red dust distribution, may be detectable in continuum colour maps. Evidence for these obscuring regions, perpendicular to the bipolar extended narrow line region (ENLR) has been detected in e.g. NGC 5252 (Tadhunter & Tsvetanov 1989; Kotilainen & Prieto 1995) and Mkn 348 (Simpson et al.1996). Similarly, continuum colour maps have revealed blue morphological features coincident with the high-excitation gas in the ENLR (e.g. Pogge & De Robertis 1993, 1995; Mulchaey et al. 1996a; KW97). In KW97, we presented high resolution colour maps of three Seyfert 1 and six Seyfert 2 galaxies. These maps revealed the existence of blue elongations and double structures in NGC  1068, NGC 3227, NGC 4151, Mkn 3 and Mkn 573, that were not discernible in single filter images, and that we interpreted as scattered nuclear light. In this paper, we present similar colour maps of the circumnuclear regions of 10 more Seyfert 2 galaxies. We briefly describe the observations, data reduction and the methods used in the construction of the colour maps in Sect. 2. In Sect. 3 we present and discuss the morphological features detected for each galaxy, including comparison with available multiwavelength data. In Sect. 4 we discuss the relevance of our findings in the enlarged sample of Seyfert galaxies, in view of current unified AGN models. Conclusions are presented in Sect. 5. Throughout this paper we use Hubble constant H₀ = 50 km s^-1 Mpc^-1, and deceleration parameter q₀ = 0.