QU Vul: An Integral Field Spectroscopy Case Study of a Nova Shell

TL;DR

This study uses high-dispersion integral field spectroscopy to analyze the 3D structure and dynamics of the nova shell QU Vul, revealing its complex morphology, velocity field, and physical properties, and providing insights into early spectral features.

Contribution

It presents the first detailed 3D tomographic analysis of QU Vul's nova shell using integral field spectroscopy, elucidating its structure, velocity, and mass distribution.

Findings

The shell is a prolate ellipsoid with specific axial ratio and inclination.

Expansion velocities are approximately 560 km/s and 400 km/s.

Distance to the nova is estimated at 1.43 kpc.

Abstract

We present GTC MEGARA high-dispersion integral field spectroscopic observations of the nova remnant QU\,Vul, which provide a comprehensive 3D view of this nova shell. The tomographic analysis of the H$\alpha$ emission reveals a complex physical structure characterized by an inhomogeneous and clumpy distribution of the material within this shell. The overall structure can be described as a prolate ellipsoid with an axial ratio of 1.4$\pm$0.2, a major axis inclination with the line of sight of $12^{\circ}\pm6^{\circ}$, and polar and equatorial expansion velocities $\approx$560 km~s$^{-1}$ and 400$\pm$60 km s$^{-1}$, respectively. The comparison of the expansion velocity on the plane of the sky with the angular expansion implies a distance of 1.43$\pm$0.23 kpc. The ionized mass is found to be $\approx 2\times 10^{-4}$ M$_\odot$, noting that the information on the 3D distribution of material within the nova shell has allowed us to reduce the uncertainty on its filling factor. The nova shell is still in its free expansion phase, which can be expected as the ejecta mass is much larger than the swept-up circumstellar medium mass. The 3D distribution and radial velocity of material within the nova shell provide an interpretation of the so-called "castellated" line profiles observed in early optical spectra of nova shells, which can be attributed to knots and clumps moving radially along different directions.