Resolving the obscuring torus in NGC 1068 with the power of infrared interferometry: Revealing the inner funnel of dust

TL;DR

This study uses high-resolution infrared interferometry to image the obscuring torus in NGC 1068, revealing its detailed structure and relation to other nuclear features, advancing understanding of active galactic nuclei.

Contribution

First to produce a detailed infrared image of NGC 1068's torus using maximum entropy reconstruction from extensive uv coverage.

Findings

The mid-infrared emission consists of two Gaussian components.

The inner funnel is hot, compact, and clumpy, aligned with water masers.

The cooler component is larger and tilted relative to the jet.

Abstract

We present new interferometric data obtained with MIDI (MID infrared Interferometric instrument) for the Seyfert II galaxy NGC 1068, with an extensive coverage of sixteen uv points. These observations resolve the nuclear mid-infrared emission from NGC 1068 in unprecedented detail with a maximum resolution of 7 mas. For the first time, sufficient uv points have been obtained, allowing us to generate an image of the source using maximum entropy image reconstruction. The features of the image are similar to those obtained by modelling. We find that the mid-infrared emission can be represented by two components, each with a Gaussian brightness distribution. The first, identified as the inner funnel of the obscuring torus, is hot (800K), 1.35 parsec long, and 0.45 parsec thick in FWHM at a PA=-42 degrees (from north to east). It has an absorption profile different than standard interstellar dust and with evidence for clumpiness. The second component is 3 by 4 pc in FWHM with T=300K, and we identify it with the cooler body of the torus. The compact component is tilted by 45 degrees with respect to the radio jet and has similar size and orientation to the observed water maser distribution. We show how the dust distribution relates to other observables within a few parsecs of the core of the galaxy such as the nuclear masers, the radio jet, and the ionization cone. We compare our findings to a similar study of the Circinus galaxy and other relevant studies. Our findings shed new light on the relation between the different parsec-scale components in NGC 1068 and the obscuring torus.