Spitzer IRAC 8 μm image showing the apertures used within SMART to extract IRS SL module spectra. The slit position is indicated by solid parallel lines. The SMART apertures are circular, each having a radius of 202. Two apertures are centered on the IRAS16399N (LINER) and IRAS16399S (SB) nuclei, respectively, the other five (ISM 1, 2, 3, 4, and 5) sample the extended envelope. The corresponding spectra are shown in Figure 5.