Panchromatic HST/WFC3 Imaging Studies of Young, Rapidly Evolving Planetary Nebulae. II. NGC 7027

TL;DR

This study provides an extensive, multi-wavelength imaging analysis of the planetary nebula NGC 7027, revealing complex structures, ionization patterns, and evolutionary processes, suggesting influences beyond single-star models, possibly involving a binary companion.

Contribution

It offers the most detailed spatial and ionization structure of NGC 7027 to date, uncovering multipolar features and complex shaping events not explained by existing single-star models.

Findings

Mapped ionization and dust extinction in detail

Identified multipolar structures driven by collimated winds

Revealed complex shaping history involving binary influence

Abstract

The iconic planetary nebula (PN) NGC 7027 is bright, nearby (D ~ 1 kpc), highly ionized, intricately structured, and well observed. This nebula is hence an ideal case study for understanding PN shaping and evolution processes. Accordingly, we have conducted a comprehensive imaging survey of NGC 7027 comprised of twelve HST Wide Field Camera 3 images in narrow-band and continuum filters spanning the wavelength range 0.243--1.67 microns. The resulting panchromatic image suite reveals the spatial distributions of emission lines covering low-ionization species such as singly ionized Fe, N, and Si, through H recombination lines, to more highly ionized O and Ne. These images, combined with available X-ray and radio data, provide the most extensive view of the structure of NGC 7027 obtained to date. Among other findings, we have traced the ionization structure and dust extinction within the nebula in sub-arcsecond detail; uncovered multipolar structures actively driven by collimated winds that protrude through and beyond the PN's bright inner core; compared the ionization patterns in the WFC3 images to X-ray and radio images of its interior hot gas and to its molecular outflows; pinpointed the loci of thin, shocked interfaces deep inside the nebula; and more precisely characterized the central star. We use these results to describe the recent history of this young and rapidly evolving PN in terms of a series of shaping events. This evolutionary sequence involves both thermal and ram pressures, and is far more complex than predicted by extant models of UV photoionization or winds from a single central progenitor star, thereby highlighting the likely influence of an unseen binary companion.