VISIR observations in the N-band. Left: the observed spectra, right: the corresponding FWHM (in arcseconds) as a function of wavelength. From top to bottom, the VISIR observations of HD 97048, HD 169142, HD 135344 B, and Oph IRS 48 are shown. The red line shows the diffraction limit for a 8.2 m telescope; the blue diamonds show the PSF values of the statistical calibrator. The 11.2 μm PAH feature in HD 97048 is more extended than the continuum (which is unresolved) and as large as the continuum for HD 169142, but smaller than the continuum in Oph IRS 48. For HD 135344 B, the continuum and PAH features are both unresolved.