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

Abstract

Context. Dust plays a significant role in planetary nebulae. Dust ejected with the gas in the asymptotic giant branch (AGB) phase is subject to the harsh environment of the planetary nebula (PN) while the star is evolving towards a white dwarf. Dust surviving the PN phase contributes to the dust content of the interstellar medium. Aims. The morphology of the internal dust extinction has been mapped for the first time in a PN, the bright nearby Galactic nebula NGC 7009. The morphologies of the gas, dust extinction and dust-to-gas ratio are compared to the structural features of the nebula. Methods. Emission line maps in H Balmer and Paschen lines were formed from analysis of MUSE cubes of NGC 7009 observed during science verification of the instrument. The measured electron temperature and density from the same cube were employed to predict the theoretical H line ratios and derive the extinction distribution across the nebula. After correction for the interstellar extinction to NGC 7009, the internal A V /N H has been mapped for the first time in a PN. Results. The extinction map of NGC 7009 has considerable structure, broadly corresponding to the morphological features of the nebula. 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× the mean ISM value. A large-scale feature in the extinction map is a wave, consisting of a crest and trough, at the rim of the inner shell. The nature of this feature is investigated and instrumental and physical causes considered; no convincing mechanisms were identified to produce this feature, other than AGB mass loss variations. Conclusions. Extinction mapping from H emission line imaging of PNe with MUSE provides a powerful tool for revealing the properties of internal dust and the dust-to-gas ratio.

Extended Structures of Planetary Nebulae Detected in H2 Emission∗

“…The locations of our targets in the Hertzsprung-Russell (H-R) diagram are shown in Figure 26, where the post-AGB evolutionary tracks calculated by Vassiliadis & Wood (1994) are presented. The effective temperatures and luminosities (as well as the uncertainties) of the PN central stars were adopted from the literature (Zhang & Kwok 1993;van Hoof et al 2000van Hoof et al , 2010Stanghellini et al 2002;Sabbadin et al 2004;Wesson & Liu 2004;Walsh et al 2016;Otsuka et al 2017). According to their locations in the H-R diagram, the central stars of our sample might be separated into two main groups: those already on the cooling track (NGC 6720, NGC 6772, NGC 6781, NGC 6894, NGC 7048, Sh 1-89), and those whose temperatures are still increasing (Hb 12,NGC 6543,NGC 6826,NGC 7009).…”

Exploring the differences of integrated and spatially resolved analysis using integral field unit data: the case of Abell 14

“…However, only a few PNe had been observed and studied with IFS, the majority of them during the last 5-6 yr (e.g. Tsamis et al 2008;Danehkar et al 2013;Monteiro et al 2013;Danehkar et al 2014;Ali et al 2015Ali et al , 2016Danehkar 2015;Danehkar & Parker 2015;Basurah et al 2016;Danehkar et al 2016;Walsh et al 2016;Dopita et al 2017Dopita et al , 2018Walsh et al 2018;Ali & Dopita 2019) and imaging fourier transform spectroscopy (Lagrois et al 2015).…”

Integral Field Spectroscopy of Planetary Nebulae with MUSE

“…Whilst it is difficult to compare distinct PNe, with a sample of only two, and chosen with diverse criteria, several points of similarity, which arise directly from the IFU spectroscopy, can be selected by a comparison of the results presented in [12,13,16]:…”

“…Comparison of the extinction, c(Hβ), maps of NGC 3132 (left, from[13]) and NGC 7009 (right, from[16]) showing strong evidence for internal dust structures obscuring background emission. The NGC 3132 image is produced in the native spaxel format, whilst the c(Hβ) image for NGC 7009 is produced from the ratio of Hα and Hβ images which have been Voronoi tesselated to a constant signal-to-noise on Hβ flux.…”