Mid Infrared Spectral Energy Distribution of NGC 1068 with 0.1 arcsec Spatial Resolution

Abstract

The central region of the Seyfert 2 galaxy NGC 1068 is imaged in the mid infrared (MIR) using the Mid-Infrared Test Observation System on the 8.2 m Subaru Telescope. The oversampling pixel scale associated with shift-and-add method shows 0.1 arcsec resolution images with a high dynamic range after deconvolution. Along with an extended structure at a position angle (P.A.) of -10 degrees with higher surface brightness, another structure extends wider with lower surface brightness at a P.A. of 20 degrees. The central peak elongates north-south with FWHM of 0.3 x 0.2 arcsec. Spectral energy distribution (SED) of the central peak is fitted to have the silicate absorption feature of tau_9.7um = 0.9 +/- 0.3. This is half of the absorption expected from the near-infrared (NIR) feature of carbonaceous dust. This suggests a temperature gradient of the absorbing dust along the line of sight. Another possibility, which is not distinguishable here, is the size distribution of dust different from our Galaxy. Intrinsic luminosity of emission from the central peak is 3 x 10^37 W. The SED shows a hint of the poly aromatic hydrocarbon (PAH) emission features. Although a high spatial resolution MIR spectrum is required, it suggests that the PAH carriers near the active galactic nuclei (AGNs) are sheltered from the high-energy emission from the AGNs and the AGNs have nuclear starbursts. For the NIR disklike structures, no counterparts are detected in the MIR. The nature of the structures remains unclear.