Probing the dusty environment of the Seyfert 1 nucleus in NGC 3783 with MIDI/VLTI interferometry

TL;DR

This study uses mid-infrared interferometry to spatially resolve and analyze the dusty environment around the Seyfert 1 nucleus of NGC 3783, supporting a clumpy, low-covering-factor dusty torus model.

Contribution

First mid-IR interferometric observations of NGC 3783's nucleus, revealing a small covering factor dust disk consistent with a clumpy AGN unification model.

Findings

Mid-IR emission consistent with an extended, clumpy dust disk or torus.

No silicate feature detected around 10 microns.

Sizes and luminosities match dust reverberation and optical/X-ray data.

Abstract

We present mid-IR spectro-interferometry of the Seyfert type 1 nucleus of NGC 3783. The dusty circumnuclear environment is spatially resolved and the wavelength dependence of the compact emission is discussed. The observations were carried out with the MIDI instrument at the Very Large Telescope Interferometer in the N-band. Spectra and visibilities were derived with a spectral resolution of 30 in the wavelength range from 8 to 13 micron. For the interpretation we developed a simple dusty disk model with small and variable covering factor. At baselines of 65 and 69 m, visibilities in the range of 0.4 to 0.7 were measured. The N-band spectra show a monotonic increase of the measured flux with wavelength with no apparent silicate feature around 10 micron. We find that the mid-IR emission from the nucleus can be reproduced by an extended dust disk or torus with a small covering factor of the radiating dust clouds. Our mid-IR observations of NGC 3783 are consistent with a clumpy circumnuclear dust environment. The interpretation in terms of a dusty torus with low covering factor supports a clumpy version of the unified scheme for AGN. The inferred sizes and luminosities are in good agreement with dust reverberation sizes and bolometric luminosities from optical and X-ray observations.