Physico-chemical spectroscopic mapping of the planetary nebula NGC 40 and the 2D_NEB, a new 2D algorithm to study ionised nebulae

TL;DR

This study uses spectroscopic mapping and introduces a new 2D algorithm, 2D_NEB, to analyze the physical and chemical conditions of the planetary nebula NGC 40, revealing spatial variations in temperature, density, and chemical abundances.

Contribution

The paper presents a novel 2D algorithm, 2D_NEB, for analyzing ionised nebulae using spectroscopic maps, validated against existing software, enabling detailed spatially-resolved physical and chemical analysis.

Findings

Temperature varies slightly across NGC 40, between ~8,000 K and ~9,500 K.

Electron densities show significant spatial variation, from ~1,000 to ~3,000 cm^(-3).

Chemical abundances also exhibit notable spatial variations.

Abstract

In this paper we present an analysis of the physical and chemical conditions of the planetary nebula NGC 40 through spatially-resolved spectroscopic maps. We also introduce a new algorithm --2D_NEB-- based on the well-established IRAF nebular package, which was developed to enable the use of the spectroscopic maps to easily estimate the astrophysical quantities of ionised nebulae. The 2D_NEB was benchmarked, and we clearly show that it works properly, since it compares nicely with the IRAF nebular software. Using this software, we derive the maps of several physical parameters of NGC 40. From these maps, we conclude that Te[NII] shows only a slight temperature variation from region to region, with its values constrained between ~8,000 K and ~9,500 K. Electron densities, on the other hand, have a much more prominent spatial variation, as Ne[SII] values vary from ~1,000 cm^(-3) to ~3,000 cm^(-3). Maps of the chemical abundances also show significant variations. From the big picture of our work, we strongly suggest that analysis with spatial resolution be mandatory for more complete study of the physical and chemical properties of planetary nebulae.