10 $\mu m$ Imaging of NGC 4151 and NGC 1068
Session 4 -- AGNs
Display presentation, Monday, 9:20-6:30, Pauley Room

[4.05] 10 $\mu m$ Imaging of NGC 4151 and NGC 1068

M. Meixner, J. R. Graham (UCB), G. W. Hawkins, C. J. Skinner (IGPP), E. Keto (LLNL), J. F. Arens, J. G. Jernigan (SSL)

We have obtained mid infrared images of the nearby Seyfert nuclei NGC 1068 and NGC 4151 to study the spatial distribution of the emission. The data were obtained at UKIRT with the Berkeley mid-IR camera which is supported by IGPP and LEA at Lawrence Livermore National Laboratory. These observations will help distinguish between thermal and non-thermal emission mechanisms, and determine the relative contribution of emission from dust in a molecular torus and the narrow line region.

The images at 8.5 and 12.5 $\mu m$ both have FWHM of $1.''3$ and very high signal to noise ($>$ 300). These data, when combined with an accurate measurement of the point spread function, permit us to constrain the sub--arcsecond structure of the emission. We confirm that the 10 $\mu m$ emission of NGC 1068 is spatially extended north--south (Becklin et al. 1976 ApJ 186 L69) but these new data show that the emission is very asymmetric. The emission consists of unresolved point source which accounts for $\simeq 40\%$ of the flux together with a jet like extended component centered 0.''3 further north. The extended component has a FWHM of 0.''88 in the north-south direction (60 $pc$ at a distance of 13 Mpc), and unresolved ($<0.''1$) east-west. The extended component is almost certainly thermal emission from dust. However, since the dust is located about 20 $pc$ from the nucleus, the emission is probably not due to dust that is in thermal equilibrium with the central engine. Rather, the emission is due to dust that is heated locally in circumnuclear star forming regions, stochastically heated small dust grains, or dust heated in the narrow line region by resonantly trapped Lyman $\alpha$.