Comparison of IRAS16399−0937 regions in "fork" diagram of 6.2 μm PAH EW vs. the silicate optical depth at 9.7 μm. Points representing the integrated spectrum of the IRAS16399−0937 system, the IRAS16399N and IRAS16399S nuclei and the ISM sub-regions are plotted using the symbols shown in the key. OHMGs from the sample of Willett et al. (2011a) are shown in red circles and the non-OHMGs are shown in blue squares. For derived errors, see Tables 4 and 5.