Near-infrared VLT adaptive optics imaging of evolved stars

TL;DR

This paper demonstrates the use of VLT adaptive optics imaging to study the detailed morphology of evolved stars and planetary nebulae, revealing complex structures and asymmetries in their circumstellar environments.

Contribution

It provides high-resolution imaging of evolved stars and planetary nebulae, uncovering new structural details and demonstrating the effectiveness of NACO AO system for such studies.

Findings

Detection of a dusty torus in Hen 2-113

Complex S-shaped nebular morphology in Roberts 22

Resolved compact dusty core in OH 231.8+4.2

Abstract

The high angular resolution and dynamic range achieved by the NACO adaptive optics system on the VLT is an excellent tool to study the morphology of Planetary Nebulae (PNe). We observed four stars in different evolutionary stages from the AGB to the PNe phase. The images of the inner parts of the PN Hen 2-113 reveal the presence of a dusty torus tilted with respect to all the other structures of the nebula and the present of hot dust close to the hot central star. The NACO observations of Roberts 22 reveal an amazingly complex nebular morphology with a S-shape that can be interpreted in terms of the 'warped disc' scenario of Icke (2003). Combined NACO and MIDI (the VLTI mid-infrared interferometer) observations of the nebula OH 231.8+4.2 have enabled us to resolve a very compact (diameter of 30-40 mas, corresponding to 40-50 a.u.) dusty structure in the core of the nebula. Finally, recent observations of the AGB star V Hydrae show that this star present a departure from spherical symmetry in its inner shell and is probably on its way to become an asymmetrical planetary nebula. These observations show that NACO is a great instrument for the discovery and study of small structures in circumstellar envelopes and PNe and a good complement to interferometric devices.