Subarcsec Emission in Seyfert Galaxies: the Nuclear Component in the L- and M -bands

We present deep L(3.8 μm) and M (4.7 μm) band imaging with ISAAC on the ESO VLT with unprecedented spatial resolution of the nearby Seyfert 2 galaxies NGC 7496 and NGC 7582 and the Seyfert 1 galaxy NGC 7213, all at comparable distance. The unresolved nuclear component dominates the emission within the central 90 pc region, while the host galaxy accounts for up to 50 % of the integrated emission at both wavelengths within the detected sizes of of ∼1 kpc in the L-band and ∼0.5 kpc in the M -band. The overall morphology of the extended component follows the general isophote pattern defined by the near-infrared continuum of the galaxies. However, the central 300 pc regions show much more ordered elliptical isophotes than in the near-infrared. In particular, emission in the Land M -bands shows well defined central point sources in the two Seyfert 2s. The brightness of the Seyfert nuclei in the LM -bands indicates that the Seyfert 2 NGC 7582 harbors as powerful nucleus as that in the Seyfert 1 NGC 7213, while the Seyfert 2 NGC 7496 is intrinsically weaker. In NGC 7582, we have detected the circumnuclear star forming ring in the L-band. Subject headings: galaxies:active – galaxies:nuclei – galaxies:Seyfert – galaxies:spiral – infrared:galaxies