Rings and arcs around evolved stars -- III. Physical conditions of the ring-like structures in the planetary nebula IC 4406 revealed by MUSE

TL;DR

This study uses VLT MUSE observations to analyze the physical conditions of ring-like structures in the planetary nebula IC 4406, revealing their electron density, temperature, and ionization state, providing new insights into nebular morphology.

Contribution

First detailed spectroscopic analysis of ring-like structures in IC 4406, determining their physical conditions and ionization state, contrasting with previous findings in other nebulae.

Findings

Rings have similar electron temperature to the main nebula rim.

Rings exhibit lower electron density than the main nebula.

Rings show a lower ionization state compared to the main cavity.

Abstract

We present the analysis of Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) observations of the planetary nebula (PN) IC 4406. MUSE images in key emission lines are used to unveil the presence of at least 5 ring-like structures North and South of the main nebula of IC 4406. MUSE spectra are extracted from the rings to unambiguously assess for the first time in a PN their physical conditions, electron density (ne) and temperature (Te). The rings are found to have similar Te than the rim of the main nebula, but smaller ne. Ratios between different ionic species suggest that the rings of IC 4406 have a lower ionization state than the main cavity, in contrast to what was suggested for the rings in NGC6543, the Cat's Eye Nebula.