A mid-infrared view of the inner parsecs of the Seyfert galaxy Mrk 1066 using CanariCam/GTC

Abstract

We present mid-infrared (MIR) imaging and spectroscopic data of the Seyfert 2 galaxy Mrk 1066 obtained with CanariCam (CC) on the 10.4 m Gran Telescopio CANARIAS (GTC). The galaxy was observed in imaging mode with an angular resolution of 0.24 arcsec (54 pc) in the Si-2 filter (8.7 micron). The image reveals a series of star-forming knots within the central ~400 pc, after subtracting the dominant active galactic nucleus (AGN) component. We also subtracted this AGN unresolved component from the 8-13 micron spectra of the knots and the nucleus, and measured equivalent widths (EWs) of the 11.3 micron Polycyclic Aromatic Hydrocarbon (PAH) feature which are typical of pure starburst galaxies. This EW is larger in the nucleus than in the knots, confirming that, at least in the case of Mrk 1066, the AGN dilutes, rather than destroys, the molecules responsible for the 11.3 micron PAH emission. By comparing the nuclear GTC/CC spectrum with the Spitzer/IRS spectrum of the galaxy, we find that the AGN component that dominates the continuum emission at wavelengths below 15 micron on scales of ~60 pc (90-100%) decreases to 35-50% when the emission of the central ~830 pc is considered. On the other hand, the AGN contribution dominates the 15-25 micron emission (75%) on the scales probed by Spitzer/IRS. We find a good match between the MIR morphology of Mrk 1066 and the extended Pab, Brg and [O III] emission. This coincidence implies that the 8.7 micron emission is probing star formation, dust in the narrow-line region, and the oval structure previously detected in the near-infrared. On the other hand, the Chandra soft X-ray morphology does not match any of the previous, contrary to what it is generally assumed for Seyfert galaxies.