Chemical Abundances of Eight Highly Extincted Milky Way Planetary Nebulae

TL;DR

This study provides detailed chemical abundance measurements of eight highly-extincted planetary nebulae in the Milky Way, using new optical spectra to enhance understanding of their compositions and galactic memberships.

Contribution

The paper presents new optical spectra and comprehensive abundance analyses of eight PNe, including kinematic classification, improving data on highly-extincted nebulae.

Findings

Determined ionic and elemental abundances for 11 elements in each nebula.

Identified galactic memberships of PNe using Gaia data.

Detected broad emission features from the central star of M 3-35.

Abstract

Low- and intermediate-mass ($\rm 0.8~M_\odot < M < 8~M_\odot$) stars that evolve into planetary nebulae (PNe) play an important role in tracing and driving Galactic chemical evolution. Spectroscopy of PNe enables access to both the initial composition of their progenitor stars and products of their internal nucleosynthesis, but determining accurate ionic and elemental abundances of PNe requires high-quality optical spectra. We obtained new optical spectra of eight highly-extincted PNe with limited optical data in the literature using the Low Resolution Spectrograph 2 (LRS2) on the Hobby-Eberly Telescope (HET). Extinction coefficients, electron temperatures and densities, and ionic and elemental abundances of up to 11 elements (He, N, O, Ne, S, Cl, Ar, K, Fe, Kr, and Xe) are determined for each object in our sample. Where available, astrometric data from Gaia eDR3 is used to kinematically characterize the probability that each object belongs to the Milky Way's thin disk, thick disk, or halo. Four of the PNe show kinematic and chemical signs of thin disk membership, while two may be members of the thick disk. The remaining two targets lack Gaia data, but their solar O, Ar, and Cl abundances suggest thin disk membership. Additionally, we report the detection of broad emission features from the central star of M 3-35. Our results significantly improve the available information on the nebular parameters and chemical compositions of these objects, which can inform future analyses.