All Figures

$\begin{figure} \par\includegraphics[width=7cm,clip]{4622f01.eps}\end{figure}$ Figure 1: Sketch of a clumpy torus. The hot and cold clouds are randomly distributed around a central accretion disk (blue). The size and optical thickness varies with radial distance.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{4622f02.eps}\end{figure}$ Figure 2: AGN source spectrum as used in our Monte Carlo simulations.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{4622f03.eps}\end{figure}$ Figure 3: Comparison of a hot-side cloud SED simulated with our Monte Carlo code mcsim_mpi (solid line) and a SED of a dust sphere with external isotropic illumination (obtained with the DUSTY code; dashed line). The Monte Carlo calculations were performed with 5 $\times$ 10⁸ photon packages (see Sect. 2.4).
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In the text

$\begin{figure} \par\includegraphics[width=5.5cm,clip]{4622f04.eps}\end{figure}$ Figure 4: Temperature profile of a simulated cloud ( $\tau _{{\rm cl}}=150$ ) with a high-resolution grid (150 $\times$ 32 cells; top) and a low-resolution grid (20 $\times$ 20 cells; bottom). The number of photon packages are 5 $\times$ 10⁸ for both simulations. The cloud was placed close to the dust sublimation radius, where the AGN is to the left. The hottest temperatures are $\sim$ 1400 K (white), the coolest are $\sim$ 200 K (dark red).
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In the text

$\begin{figure} \par\includegraphics[width=12cm,clip]{4622f05.eps}\end{figure}$ Figure 5: SEDs of spherical dust clouds with optical depths of $\tau _{{\rm cl}}=70$ simulated with our Monte Carlo code mcsim_mpi. In the upper row, the panels represent clouds at distances $r=r_{\rm subl}$ and $r=2~ r_{\rm subl}$ ; in the lower row they represent clouds at distances $r=4~ r_{\rm subl}$ and $r=8~ r_{\rm subl}$ . For each cloud three SEDs are shown, as seen under phase angles of $\phi =160\hbox {$^\circ $ }$ (green), $\phi =110\hbox {$^\circ $ }$ (black), and $\phi =60\hbox {$^\circ $ }$ (red). In terms of illumination, these phase angles correspond to 3%, 33%, and 75%, respectively. The absolute flux values are normalized to the cloud surfaces.
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In the text

$\begin{figure} \par\includegraphics[width=7.1cm,clip]{4622f06.eps}\end{figure}$ Figure 6: Model SEDs of the unilluminated side of dust clouds at two different distances from the central source. The silicate feature is in absorption. The solid and the dashed SEDs represent clouds at $2~ r_{\rm subl}$ with $\tau _{{\rm cl}}=100$ and $\tau _{{\rm cl}}=400$ , respectively. The dashed-dotted SED comes from a cloud at $4~ r_{\rm subl}$ and $\tau _{{\rm cl}}=250$ .
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In the text

$\begin{figure} \par\includegraphics[width=13.8cm,clip]{4622f07.eps}\end{figure}$ Figure 7: Torus SEDs of 10 different random cloud arrangements for the set of parameters listed in Table 3. The panels in the first row show SEDs for inclinations of $i=90\hbox {$^\circ $ }$ (edge-on; left) and $i=45\hbox {$^\circ $ }$ ( right); the panels in the second row show $i=30\hbox {$^\circ $ }$ ( left) and $i=0\hbox {$^\circ $ }$ (pole-on; right).
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In the text

$\begin{figure} \par\includegraphics[width=5.15cm,clip]{4622f08a.eps}\includegrap... ...clip]{4622f08k.eps}\includegraphics[width=5.15cm,clip]{4622f08l.eps}\end{figure}$ Figure 8: L-band model images of the torus described by the parameters listed in Table 3 (same parameters as used for the SED calculations shown in Fig. 7). Left column: images obtained by averaging model images of $\sim$ 200 different random cloud arrangements. Middle and right columns: model images for two particular random cloud arrangements. From top to bottom: $i=90\hbox {$^\circ $ }$ , $45\hbox {$^\circ $ }$ , $30\hbox {$^\circ $ }$ , and $0\hbox {$^\circ $ }$ .
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In the text

$\begin{figure} \par\includegraphics[width=5.25cm,clip]{4622f09.eps}\end{figure}$ Figure 9: K-band model image for non-isotropic, sinusoidal radiation from the accretion disk for one particular random cloud arrangement, edge-on view, and model parameters listed in Table 3.
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In the text

$\begin{figure} \par\includegraphics[width=13.8cm,clip]{4622f10.eps}\end{figure}$ Figure 10: The dependence of the SED on $\eta _r$ (model parameters in Table 3). The upper panels show edge-on SEDs for 10 different random cloud arrangements for a=1.0 ( left) and a=1.5 ( right). In the lower left panel we present the edge-on view for a=2.0, while the lower right panel combines pole-on views of the three models with a=1.0 ( top), a=1.5 ( middle), and a=2.0 ( bottom).
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In the text

$\begin{figure} \par\includegraphics[width=13.8cm,clip]{4622f11.eps}\end{figure}$ Figure 11: SEDs for different flaring (see text; model parameters in Table 3). From upper left to lower right: $H \propto r^{0.5}$ , r^1.0, r^1.2, and r^1.5, respectively. Each panel consists of SEDs for 10 different random cloud arrangements seen edge-on (black) and pole-on (red).
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{4622f12.eps}\end{figure}$ Figure 12: SEDs for outer radii of $r_{\rm o}=70~ r_{\rm subl}$ (black) and $r_{\rm o}=30~ r_{\rm subl}$ (red) seen edge-on and pole-on (model parameters in Table 3).
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7cm,clip]{4622f13.eps}\end{figure}$ Figure 13: Comparison between the observed high-resolution SED of NGC 1068 (blue diamonds and red curve) and our model SED (model parameters in Table 5). The red line represents the total MIDI flux (Jaffe et al. 2004). The shaded area shows the range of model SED variations obtained for 10 different random cloud arrangements. The dark grey line is the average of the 10 individual model SEDs.
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=7cm,clip]{4622f14.eps}\end{figure}$ Figure 14: Comparison between the K-band model visibilities (grey lines; model parameters of Table 5) for 10 different random cloud arrangements and the observed visibilities (red symbols) at 0-6 m and 46 m baseline at PA 45 $^\circ$ . The green dashed-dotted line shows a Gaussian profile with 28 mas FWHM (=2.0 pc; see Table 6).
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In the text

$\begin{figure} \par\includegraphics[angle=90,width=11.65cm,clip]{4622f15.eps}\end{figure}$ Figure 15: Comparison between the observed NGC 1068 MIDI visibilities (red line) at projected baselines of 42 m ( upper panel) and 78 m ( lower panel), and our model visibilities (model parameters in Table 5). The grey lines show the visibilities for 10 different random cloud arrangements. The blue line represents the average model visibility.
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In the text

$\begin{figure} \par\includegraphics[width=5.15cm,clip]{4622f16a.eps}\includegrap... ...clip]{4622f16e.eps}\includegraphics[width=5.15cm,clip]{4622f16f.eps}\end{figure}$ Figure 16: NGC 1068 model images of our clumpy torus model described in Table 5. From left to right: K-, M-, and N-band images for an inclination angle of $i=55\hbox {$^\circ $ }$ . The upper row shows images obtained for one particular random cloud arrangement, whereas the images in the lower row are averages of over $\sim$ 200 different random cloud arrangements. The grainy structure in the images in the upper row is caused by the clumpiness of the torus.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{4622f01.eps}\end{figure}$	Figure 1: Sketch of a clumpy torus. The hot and cold clouds are randomly distributed around a central accretion disk (blue). The size and optical thickness varies with radial distance.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{4622f02.eps}\end{figure}$	Figure 2: AGN source spectrum as used in our Monte Carlo simulations.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{4622f03.eps}\end{figure}$	Figure 3: Comparison of a hot-side cloud SED simulated with our Monte Carlo code mcsim_mpi (solid line) and a SED of a dust sphere with external isotropic illumination (obtained with the DUSTY code; dashed line). The Monte Carlo calculations were performed with 5 $\times$ 10⁸ photon packages (see Sect. 2.4).
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$\begin{figure} \par\includegraphics[width=7.1cm,clip]{4622f06.eps}\end{figure}$	Figure 6: Model SEDs of the unilluminated side of dust clouds at two different distances from the central source. The silicate feature is in absorption. The solid and the dashed SEDs represent clouds at $2~ r_{\rm subl}$ with $\tau _{{\rm cl}}=100$ and $\tau _{{\rm cl}}=400$ , respectively. The dashed-dotted SED comes from a cloud at $4~ r_{\rm subl}$ and $\tau _{{\rm cl}}=250$ .
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$\begin{figure} \par\includegraphics[width=13.8cm,clip]{4622f07.eps}\end{figure}$	Figure 7: Torus SEDs of 10 different random cloud arrangements for the set of parameters listed in Table 3. The panels in the first row show SEDs for inclinations of $i=90\hbox {$^\circ $ }$ (edge-on; left) and $i=45\hbox {$^\circ $ }$ ( right); the panels in the second row show $i=30\hbox {$^\circ $ }$ ( left) and $i=0\hbox {$^\circ $ }$ (pole-on; right).
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$\begin{figure} \par\includegraphics[width=5.25cm,clip]{4622f09.eps}\end{figure}$	Figure 9: K-band model image for non-isotropic, sinusoidal radiation from the accretion disk for one particular random cloud arrangement, edge-on view, and model parameters listed in Table 3.
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$\begin{figure} \par\includegraphics[width=13.8cm,clip]{4622f11.eps}\end{figure}$	Figure 11: SEDs for different flaring (see text; model parameters in Table 3). From upper left to lower right: $H \propto r^{0.5}$ , r^1.0, r^1.2, and r^1.5, respectively. Each panel consists of SEDs for 10 different random cloud arrangements seen edge-on (black) and pole-on (red).
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$\begin{figure} \par\includegraphics[width=7.4cm,clip]{4622f12.eps}\end{figure}$	Figure 12: SEDs for outer radii of $r_{\rm o}=70~ r_{\rm subl}$ (black) and $r_{\rm o}=30~ r_{\rm subl}$ (red) seen edge-on and pole-on (model parameters in Table 3).
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$\begin{figure} \par\includegraphics[angle=90,width=7cm,clip]{4622f13.eps}\end{figure}$	Figure 13: Comparison between the observed high-resolution SED of NGC 1068 (blue diamonds and red curve) and our model SED (model parameters in Table 5). The red line represents the total MIDI flux (Jaffe et al. 2004). The shaded area shows the range of model SED variations obtained for 10 different random cloud arrangements. The dark grey line is the average of the 10 individual model SEDs.
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$\begin{figure} \par\includegraphics[angle=90,width=7cm,clip]{4622f14.eps}\end{figure}$	Figure 14: Comparison between the K-band model visibilities (grey lines; model parameters of Table 5) for 10 different random cloud arrangements and the observed visibilities (red symbols) at 0-6 m and 46 m baseline at PA 45 $^\circ$ . The green dashed-dotted line shows a Gaussian profile with 28 mas FWHM (=2.0 pc; see Table 6).
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$\begin{figure} \par\includegraphics[angle=90,width=11.65cm,clip]{4622f15.eps}\end{figure}$	Figure 15: Comparison between the observed NGC 1068 MIDI visibilities (red line) at projected baselines of 42 m ( upper panel) and 78 m ( lower panel), and our model visibilities (model parameters in Table 5). The grey lines show the visibilities for 10 different random cloud arrangements. The blue line represents the average model visibility.
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