``ISOCAM Observations of the Seyfert 2 galaxy NGC 3147''
by
Laurent, O., Mirabel, I.F., Charmandaris, V., Sauvage, M., Gallais, P., Vigroux, L. & Cesarsky, C.J.
Service d'Astrophysique/DAPNIA/DSM, CEA Saclay
F-91191, Gif-sur-Yvette, France

Rencontres de Moriond, ``Extragalactic Astronomy in the Infrared'', 1997, p.311

We have obtained mid-infrared maps of the face-on Seyfert 2 galaxy NGC 3147. Its average properties are typical of normal galaxies. However, the mid-infrared properties of the Seyfert nucleus and the immediate environment are peculiar. The nucleus presents low silicate absorption and low emission from Polycyclic Aromatic Hydrocarbon (PAH) which suggest that we observe a hot inner dusty torus with a radius smaller than 0.6 kpc. Between 0.6 Kpc and 1.2 Kpc from the center, there is an extended PAH emission which may be attributed to the narrow line region (NRL) heated directly by the non-thermal emission of the active galactic nucleus (AGN). A star forming ring at 2-2.5kpc from the center is observed in the mid-infrared. Beyond this ring, the thermal emission near the strong star forming regions (SFRs) increases faster than the PAH emission. The ratio of 7 $\mum$ to 15 $\mum$ flux is less than 1 in star forming regions and becomes close to 1 outside these regions. Even though the star formation rate is very high in the ring, we still detect PAH emissions which suggest that PAHs are not completely destroyed in starburst regions.

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