Mid-infrared observations of NGC 1068 with the Infrared Space Observatory

We report on Mid-Infrared (MIR) observations of the Seyfert 2 galaxy NGC 1068, obtained with ISOCAM in low-resolution spectro-imaging mode. The spatial resolution (similar to5 ) allows us to disentangle the circumnuclear starburst regions from the emission of the active galactic nucleus (AGN). The global spatial distribution of the Unidentified Infrared Bands (UIBs) is similar to the cold dust component, traced by the 450 mum emission and the gaseous component obtained from the (CO)-C-12(1-0) map. However, a shift between the maximum of the UIB and 450 mum emission is clearly seen in our maps. Thr UIBs ill the MIR (5-16 mum) originate almost exclusively from the starburst regions in the galactic disk with an emission peaking at the extremity of the stellar/gaseous bar at a distance of 1 kpc from the AGN. The spectrum of the nucleus is characterized over the whole 5-16 mum range by a strong continuum which carl be fitted with a power lan of index alpha = -1.7. Moreover, the high [NeIII]/[NEII] ratio (greater than or similar to 2.5) in the nuclear region argues for a hard radiation held front the AGN. Observations indicate that the AGN in NGC 1068 contributes less than similar to5% to the total integrated UIB emission even though its hut dust continuum contributes as much as 75% to the total MIR flux. On the contrary., the nuclear contribution to the cold dust emission decreases considerably at submillimeter wavelengths and does not represent more than 2.5% of the total integrated emission at 450 mum.