Near-IR Images of the Torus and Micro-Spiral Structure in NGC 1068 using Adaptive Optics

TL;DR

This study uses adaptive optics to produce high-resolution near-infrared images of NGC 1068's nucleus, revealing detailed structures like a dust torus and micro-spiral arms, enhancing understanding of its central region.

Contribution

First near-IR diffraction-limited images of NGC 1068's nucleus revealing the torus and micro-spiral structures with unprecedented detail.

Findings

Resolved the unresolved core associated with the central engine.

Detected a S-shaped micro-spiral structure within 20 pc.

Identified the elongated dust structure perpendicular to the radio jet.

Abstract

We present diffraction-limited near-IR images in J, H and K of the nucleus of NGC 1068, obtained with the Adaptive Optics system {Pueo} at CFHT. The achieved resolution (0.12") reveals several components, particularly prominent on the [J-K] image: a) an unresolved, conspicuous core (size < 9 pc); b) an elongated structure at P.A. ~102 deg, beginning to show up at radius ~ 15 pc; c) a S-shaped structure with radial extent ~ 20 pc, including a bar-like central elongation at P.A. ~ 15 deg and two short spiral arms. The K core is at the location of the putative central engine (radio source S1) : the core is likely the emission from the hot inner walls of the dust/molecular torus. The extremely red colors of the central 0.2", [J-K]=7.0, [H-K]=3.8, lead to an extinction Av > 25. The elongated structure at P.A.~ 102 deg may trace the presence of cooler dust within and around the torus. This interpretation is supported by two facts : a) the elongated structure is perpendicular to the local radio jet originating at S1; b) its direction follows exactly that of the disk of ionized gas recently found with the VLBA. The S-shaped feature suggests an extremely compact barred spiral structure, that would be the innermost of a series of nested spiral structures, as predicted by simulations. This is supported by the inner stellar distribution - deduced from the J image - which clearly follows an exponential disk with a 19 pc scale-length, precisely that expected from the rotation of a bar.