The extinction and dust-to-gas structure of the planetary nebula NGC 7009 observed with MUSE

TL;DR

This study uses MUSE observations to map the dust-to-gas ratio and extinction structure in the planetary nebula NGC 7009, revealing complex internal dust distribution and variations in dust-to-gas ratio across the nebula.

Contribution

First mapping of the internal dust-to-gas ratio in a planetary nebula using MUSE, showing detailed extinction structure and dust distribution.

Findings

Extinction map shows complex structure aligned with nebula morphology.

Dust-to-gas ratio increases from center to periphery, exceeding interstellar values.

Extinction mapping with MUSE is effective for studying dust in planetary nebulae.

Abstract

The large field and wavelength range of MUSE is well suited to mapping Galactic planetary nebulae (PN). The bright PN NGC 7009 was observed with MUSE on the VLT during the Science Verification of the instrument in seeing of 0.6". Emission line maps in hydrogen Balmer and Paschen lines were formed from analysis of the MUSE cubes. The measured electron temperature and density from the MUSE cube were employed to predict the theoretical hydrogen line ratios and map the extinction distribution across the nebula. After correction for the interstellar extinction to NGC 7009, the internal dust-to-gas ratio (A_V/N_H) has been mapped for the first time in a PN. The extinction map of NGC 7009 has considerable structure, broadly corresponding to the morphological features of the nebula. A large-scale feature in the extinction map, consisting of a crest and trough, occurs at the rim of the inner shell. The nature of this feature was investigated and instrumental and physical causes considered; no convincing mechanisms were identified to produce this feature, other than mass loss variations in the earlier asymptotic giant branch phase. The dust-to-gas ratio A_V/N_H increases from 0.7 times the interstellar value to >5 times from the centre towards the periphery of the ionized nebula. The integrated A_V/N_H is about 2 times the mean ISM value. It is demonstrated that extinction mapping with MUSE provides a powerful tool for studying the distribution of PN internal dust and the dust-to-gas ratio. (Abridged.)