Observational Study of the Multistructured Planetary Nebula NGC 7354

TL;DR

This study provides a detailed observational and modeling analysis of planetary nebula NGC 7354, revealing its complex multi-structured morphology, physical conditions, and a proposed formation scenario based on imaging, spectroscopy, and 3D modeling.

Contribution

It offers a comprehensive multi-wavelength observational dataset and a detailed 3D morphokinematic model of NGC 7354, enhancing understanding of its structure and formation.

Findings

NGC 7354 has four main structures: outer shell, inner shell, bright knots, and jet-like features.

Physical parameters vary slightly across the nebula, with abundance values mostly within uncertainties.

The SHAPE model accurately reproduces observed structures and suggests a formation scenario.

Abstract

We present an observational study of the planetary nebula (PN) NGC 7354 consisting of narrowband Halpha and [NII]6584 imaging as well as low- and high-dispersion long-slit spectroscopy and VLA-D radio continuum. According to our imaging and spectroscopic data, NGC 7354 has four main structures: a quite round outer shell and an elliptical inner shell, a collection of low-excitation bright knots roughly concentrated on the equatorial region of the nebula, and two symmetrical jet-like features, not aligned either with the shells' axes, or with each other. We have obtained physical parameters like electron temperature and electron density as well as ionic and elemental abundances for these different structures. Electron temperature and electron density slightly vary throughout the nebula. The local extinction coefficient c_Hbeta shows an increasing gradient from south to north and a decreasing gradient from east to west consistent with the number of equatorial bright knots present in each direction. Abundance values show slight internal variations but most of them are within the estimated uncertainties. In general, abundance values are in good agreement with the ones expected for PNe. Radio continuum data are consistent with optically thin thermal emission. We have used the interactive three-dimensional modeling tool SHAPE to reproduce the observed morphokinematic structures in NGC 7354 with different geometrical components. Our SHAPE model is in very good agreement with our imaging and spectroscopic observations. Finally, after modeling NGC 7354 with SHAPE, we suggest a possible scenario for the formation of the nebula.