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$\begin{figure} \par\includegraphics[width=7cm,clip]{8466fg01.ps} \end{figure}$ Figure 1: ISAAC L-band spectra of sample with 3.3 $\mu$ m PAH detection.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{8466fg02.ps} \end{figure}$ Figure 2: ISAAC L-band spectra of sample without 3.3 $\mu$ m PAH detection.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{8466fg03.ps} \end{figure}$ Figure 3: VISIR N-band spectra of the sources with PAH detections.
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In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{8466fg04.ps} \end{figure}$ Figure 4: VISIR N-band spectra of the sources with marginal (top 4) and no PAH detections (bottom 2).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg05.ps} \end{figure}$ Figure 5: ( Upper panel) ISAAC L-band spectrum of HD 100546, scaled by a factor 1.25 to match the ISO spectrum and then shifted by +4 Jy for clarity. The grey band highlights the position and FWHM of the 3.3 $\mu$ m PAH feature as determined in this paper. ( Lower panel) FWHM of the spatial profile, as extracted from 2D spectral image, of HD100546 ( black line) and its corresponding standard HR 4757 ( grey line). The FWHM of the latter agrees with that of the HD 100546 continuum after correction for airmass and seeing differences.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg06.ps} \end{figure}$ Figure 6: ( Upper panel) ISAAC L-band spectrum of TY CrA. ( Lower panel) FWHM of spatial profile of TY CrA and standard star HR 5812.
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In the text

$\begin{figure} \par\includegraphics[width=8.3cm,clip]{8466fg07.eps} \end{figure}$ Figure 7: Observed spatial emission profiles for WL 16 ( left), IRS 48 ( middle), and TY CrA ( right), for the PAH feature at indicated wavelength (solid line) and continuum emission at 10.51, 3.56, and 3.35 $\mu$ m respectively (dashed line).
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In the text

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{8466fg08.ps} \end{figure}$ Figure 8: ( Upper panel) VISIR N-band spectrum of WL 16. ( Lower panel) FWHM of spatial profile of WL 16 and standard star HR 6879.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg09.eps} \end{figure}$ Figure 9: VISIR 2D spectral image of SR 21A ( left) and WL 16 ( right); 1 pixel = 0.02719''.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg10.ps} \end{figure}$ Figure 10: ( Upper-left panel) NACO L-band spectrum of WL 16, slit parallel to semi-major axis of the disk. ( Lower-left panel) FWHM of spatial profile of the "parallel'' observation of WL 16 (black) and standard star HD 142378 (grey). ( Upper-right panel) NACO L-band spectrum of WL 16, slit perpendicular to semi-major axis of the disk. ( Lower panel) FWHM of spatial profile of the "perpendicular'' observation of WL 16 (black) and standard star HD 142378 (grey).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg11.ps} \end{figure}$ Figure 11: ( Upper panel) ISAAC L-band spectrum of SR 21A. ( Lower panel) FWHM of spatial profile of SR 21A and standard star HR 6629.
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8466fg12.ps} \end{figure}$ Figure 12: ( Upper panel) VISIR N-band spectrum of SR 21A. ( Lower panel) FWHM of spatial profile of SR 21A and standard star HR 6879.
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8466fg13.ps} \end{figure}$ Figure 13: ( Upper panel) VISIR N-band spectrum of IRS 48. ( Lower panel) FWHM of spatial profile of IRS 48 and standard star Alnair.
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8466fg14.ps} \end{figure}$ Figure 14: ( Upper panel) NACO L-band spectrum of IRS 48. ( Lower panel) FWHM of spatial profile of IRS 48 and standard star HD 142378.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{8466fg15.eps} \end{figure}$ Figure 15: Radial extent of 3.3 $\mu$ m feature versus 11.2 $\mu$ m feature; Herbig Ae stars indicated by filled diamonds, T Tauri stars by filled triangles; models with $N_{{\rm c}}$ = 96 indicated by grey, $N_{{\rm c}}$ =50 by black. Observations of IRS 48, SR 21A, T Cha, HD 101412 and HD 98922 are indicated by open symbols. Model prediction point extracted from Fig. 4 of Habart et al. (2004) for a disk around a Herbig star for $N_{{\rm c}} = 100$ is indicated by a cross.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg16.eps}\end{figure}$ Figure A.1: Normalized cumulative intensity of the five main PAH features (black) and the continua at 3.1 and 19.6 $\mu$ m (gray) for ${\rm C}_{50}^{}{\rm H}_{18}^{}$ and ${\rm C}_{96}^{}{\rm H}_{24}^{}$ in the standard Herbig Ae/Be and T Tauri model disks (including PAH chemistry) from Visser et al. (2007). The disks were synthetically observed face-on through an infinitely wide slit. The vertical bars indicate where each curve reaches $76\%$ , corresponding to the HWHM of the Gaussians in Sect. 2.5.

In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg17.eps}\end{figure}$ Figure A.2: Normalized cumulative intensity for ${\rm C}_{50}^{}{\rm H}_{18}^{}$ in the standard Herbig Ae/Be model disk (including PAH chemistry) from Visser et al. (2007). The disk was synthetically observed at $45^\circ$ or through a narrow slit as indicated. Lines and colors are as in Fig. A.1.

In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{8466fg01.ps} \end{figure}$	Figure 1: ISAAC L-band spectra of sample with 3.3 $\mu$ m PAH detection.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{8466fg02.ps} \end{figure}$	Figure 2: ISAAC L-band spectra of sample without 3.3 $\mu$ m PAH detection.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{8466fg03.ps} \end{figure}$	Figure 3: VISIR N-band spectra of the sources with PAH detections.
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$\begin{figure} \par\includegraphics[width=7cm,clip]{8466fg04.ps} \end{figure}$	Figure 4: VISIR N-band spectra of the sources with marginal (top 4) and no PAH detections (bottom 2).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg06.ps} \end{figure}$	Figure 6: ( Upper panel) ISAAC L-band spectrum of TY CrA. ( Lower panel) FWHM of spatial profile of TY CrA and standard star HR 5812.
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$\begin{figure} \par\includegraphics[width=8.3cm,clip]{8466fg07.eps} \end{figure}$	Figure 7: Observed spatial emission profiles for WL 16 ( left), IRS 48 ( middle), and TY CrA ( right), for the PAH feature at indicated wavelength (solid line) and continuum emission at 10.51, 3.56, and 3.35 $\mu$ m respectively (dashed line).
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$\begin{figure} \par\includegraphics[width=7.3cm,clip]{8466fg08.ps} \end{figure}$	Figure 8: ( Upper panel) VISIR N-band spectrum of WL 16. ( Lower panel) FWHM of spatial profile of WL 16 and standard star HR 6879.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg09.eps} \end{figure}$	Figure 9: VISIR 2D spectral image of SR 21A ( left) and WL 16 ( right); 1 pixel = 0.02719''.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{8466fg11.ps} \end{figure}$	Figure 11: ( Upper panel) ISAAC L-band spectrum of SR 21A. ( Lower panel) FWHM of spatial profile of SR 21A and standard star HR 6629.
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$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8466fg12.ps} \end{figure}$	Figure 12: ( Upper panel) VISIR N-band spectrum of SR 21A. ( Lower panel) FWHM of spatial profile of SR 21A and standard star HR 6879.
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$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8466fg13.ps} \end{figure}$	Figure 13: ( Upper panel) VISIR N-band spectrum of IRS 48. ( Lower panel) FWHM of spatial profile of IRS 48 and standard star Alnair.
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$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8466fg14.ps} \end{figure}$	Figure 14: ( Upper panel) NACO L-band spectrum of IRS 48. ( Lower panel) FWHM of spatial profile of IRS 48 and standard star HD 142378.
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