3D Photoionisation Modelling of NGC 6302

TL;DR

This paper presents a detailed 3D photoionisation and dust radiative transfer model of NGC 6302, revealing the nebula's density distribution, the properties of its central star, and dust characteristics, shedding light on its extreme nature and evolution.

Contribution

The study introduces a comprehensive 3D modeling approach for NGC 6302, including a novel fit to its optical and infrared spectra, and suggests the central star may have experienced a late thermal pulse.

Findings

Best fit with a 220,000 K hydrogen-deficient star model

Dust grains up to 1.0 micron size within a recessed circumstellar disk

Constraints on the nebula's density distribution and evolutionary history

Abstract

We present a three-dimensional photoionisation and dust radiative transfer model of NGC 6302, an extreme, high-excitation planetary nebula. We use the 3D photoionisation code Mocassin} to model the emission from the gas and dust. We have produced a good fit to the optical emission-line spectrum, from which we derived a density distribution for the nebula. A fit to the infrared coronal lines places strong constraints on the properties of the unseen ionising source. We find the best fit comes from using a 220,000 K hydrogen-deficient central star model atmosphere, indicating that the central star of this PN may have undergone a late thermal pulse. We have also fitted the overall shape of the ISO spectrum of NGC 6302 using a dust model with a shallow power-law size distribution and grains up to 1.0 micron in size. To obtain a good fit to the infrared SED the dust must be sufficiently recessed within the circumstellar disk to prevent large amounts of hot dust at short wavelengths, a region where the ISO spectrum is particularly lacking. These and other discoveries are helping to unveil many properties of this extreme object and trace it's evolutionary history.