The nuclear and extended infrared emission of the Seyfert galaxy NGC 2992 and the interacting system Arp 245

Abstract

We present subarcsecond resolution infrared (IR) imaging and mid-IR (MIR) spectroscopic observations of the Seyfert 1.9 galaxy NGC 2992, obtained with the Gemini North Telescope and the Gran Telescopio CANARIAS (GTC). The N-band image reveals faint extended emission out to ∼3 kpc, and the polycyclic aromatic hydrocarbon features detected in the GTC/CanariCam 7.5–13 μm spectrum indicate that the bulk of this extended emission is dust heated by star formation. We also report arcsecond resolution MIR and far-IR imaging of the interacting system Arp 245, taken with the Spitzer Space Telescope and the Herschel Space Observatory. Using these data, we obtain nuclear fluxes using different methods and find that we can only recover the nuclear fluxes obtained from the subarcsecond data at 20–25 μm, where the active galactic nuclei (AGN) emission dominates. We fitted the nuclear IR spectral energy distribution of NGC 2992, including the GTC/CanariCam nuclear spectrum (∼50 pc), with clumpy torus models. We then used the best-fitting torus model to decompose the Spitzer/IRS 5–30 μm spectrum (∼630 pc) in AGN and starburst components, using different starburst templates. We find that, whereas at shorter MIR wavelengths the starburst component dominates (64 per cent at 6 μm), the AGN component reaches 90 per cent at 20 μm. We finally obtained dust masses, temperatures and star formation rates for the different components of the Arp 245 system and find similar values for NGC 2992 and NGC 2993. These measurements are within those reported for other interacting systems in the first stages of the interaction.

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