Mapping and Spectroscopy of the Planetary Nebula NGC 7009 in the Visual and Infrared

TL;DR

This study combines visual and infrared spectroscopy and imaging to analyze the structure, composition, and excitation mechanisms of the planetary nebula NGC 7009, revealing insights into its dust, crystalline silicates, and shock features.

Contribution

It provides a comprehensive multi-wavelength analysis of NGC 7009, highlighting the presence of crystalline silicates and shock excitation evidence, which advances understanding of planetary nebulae composition and dynamics.

Findings

Mid-infrared continuum dominated by ~100K emission

Detection of crystalline silicate features similar to Forsterite and enstatite

Evidence of shock excitation at nebula edges and ansae

Abstract

NGC 7009 is a fascinating example of a high excitation, elliptical planetary nebula (PN) containing circum-nebular rings, and FLIERs and jets along the major axis. We present visual spectroscopy along multiple position angles through the nucleus, taken with the Observatorio Astronomico Nacional (Mexico); mid-infrared (MIR) spectroscopy and imaging acquired using the Infrared Space Observatory (ISO) and Spitzer Space Telescope (SST), and narrow band imaging obtained using the Hubble Space Telescope (HST). The data show that the mid-infrared (MIR) continuum is dominated by a broad ~ 100K continuum, and a strong excess attributable to crystalline silicate emission. The primary peaks in this excess are similar to those observed in Forsterite and clino- and ortho-enstatite. We use the ground-based spectroscopy, and ratioing of HST images to investigate the presence of shocks in the ansae and interior envelope. It is concluded that line ratios in the ansae may be partially consistent with shock excitation, although these features are primarily dominated by photo-ionisation. We also note evidence for shock excitation at the limits of the interior elliptical shell, and for multiple bow-shock structures centered upon the ansae.