Searching for AGN signatures in Mid-IR Spectra: The case of NGC1068
  We present mid-IR observations of the prototypical Seyfert 2 galaxy NGC 1068 obtained with ISOCAM between 5 and 16micron. The proximity of this galaxy coupled with the spectro-imaging capabilities of the instrument allow us to separate the mid-IR emission of the active galactic nucleus (AGN) from the distinctly different emission of the circumnuclear star forming regions. The Unidentified Infrared Bands (UIBs), which trace the starburst contribution very well, are not detected in the spectrum of the AGN region where their carriers could be destroyed. Moreover, the featureless continuum of the AGN exhibits a strong hot dust component below 10micron not observed in the starburst regions. Those two distinct mid-IR spectral properties, as well as the presence of high excitation ionic lines such as [NeVI](7.7micron) and [NeV](14.3micron) in the AGN spectrum, provide us with very powerful complementary tools to disentangle AGNs from starbursts. The effects of high extinction on the mid-IR identification of AGNs are also discussed. 
O. Laurent, I.F. Mirabel, V. Charmandaris, E. Le Floc'h, D. Lutz and   R. Genzel