HR Del remnant anatomy using 2-D spectral data and 3-D photoionization shell models

TL;DR

This study combines spectral data and 3D photoionization models to analyze the complex, clumpy structure and composition of the HR Del nova remnant, revealing detailed morphology, abundance gradients, and ionization properties.

Contribution

It introduces a novel 3D clumpy shell model with an ionization disk source that explains observed morphological and ionization features of the HR Del remnant.

Findings

Shell has a clumpy, hourglass shape with symmetric rings.

Outer shell regions are less abundant in Oxygen and Nitrogen.

Model estimates shell mass at 9 x 10^-4 solar masses, with significant neutral clumps.

Abstract

The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in H-alpha, that forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman and O'Brien (2003). The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structure seen only in the [OIII] and [NII] maps is located along the polar directions inside the hourglass structure. Abundances gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in Oxygen and Nitrogen than the inner regions. Detailed 2.5D photoionization modeling of the 3D shell was performed using the mass distribution inferred from the observations and the presence of mass clumps. The resulting model grids are used to constrain the physical properties of the shell as well as the central ionizing source. A sequence of 3D clumpy models including a disk shaped ionization source is able to reproduce the ionization gradients between polar and equatorial regions of the shell. Differences between shell axial ratios in different lines can also be explained by aspherical illumination. A total shell mass of 9 x 10-4 Msun is derived from these models. We estimate that 50% to 70% of the shell mass is contained in neutral clumps with density contrast up to a factor of 30.