Abstract
We present near-infrared interferometric data on the Seyfert 2 galaxy NGC 1068, obtained with the GRAVITY instrument on the European Southern Observatory Very Large Telescope Interferometer. The extensive baseline coverage from 5 to 60 Mλ allowed us to reconstruct a continuum image of the nucleus with an unrivaled 0.2 pc resolution in the K-band. We find a thin ring-like structure of emission with a radius r = 0.24 ± 0.03 pc, inclination i = 70 ± 5°, position angle PA = −50 ± 4°, and h/r < 0.14, which we associate with the dust sublimation region. The observed morphology is inconsistent with the expected signatures of a geometrically and optically thick torus. Instead, the infrared emission shows a striking resemblance to the 22 GHz maser disc, which suggests they share a common region of origin. The near-infrared spectral energy distribution indicates a bolometric luminosity of (0.4–4.7) × 1045 erg s−1, behind a large AK ≈ 5.5 (AV ≈ 90) screen of extinction that also appears to contribute significantly to obscuring the broad line region.
Highlights
NGC 1068 is often regarded as an archetypical Seyfert 2 galaxy (e.g. Bland-Hawthorn et al 1997)
The subsequent incorporation of a clumpy structure led to a suite of models that provide very good fits to the near-to-mid infrared spectral energy distribution (SED) of many active galactic nuclei (AGN) (Nenkova et al 2008; Hönig et al 2006; Stalevski et al 2012), and which are consistent with dust reverberation measurements (Koshida et al 2014)
Adopting anisotropic emission from the accretion disc as described by Netzer (2015) L ∝ cos(θ)[1 + b cos(θ)] with b 2, we find that about 10% of the AGN luminosity is intersected by a surrounding disc with h/r < 0.14 when the accretion disc is tilted by 40◦
Summary
NGC 1068 is often regarded as an archetypical Seyfert 2 galaxy (e.g. Bland-Hawthorn et al 1997). GarcíaBurillo et al (in prep.) detected the molecular disc in CO(2-1) and (3-2) at a PA ∼115 ◦ with an extension of 30 pc Taken together, these observations, while still being consistent with and requiring the existence of a nuclear obscuring structure, are incompatible with geometrically thick clumpy torus models that attempt to account for all of the nuclear nearto-mid infrared continuum. A magnetocentrifugal wind is launched at the boundary between the discs, and accounts for the elongated polar structures seen in many MIR interferometric measurements (López-Gonzaga et al 2016) This multi-component model was able to account for a wide variety of detailed observations when applied to NGC 1068.
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