Analysis of Planetary Nebulae in the Milky Way: Physical Properties, Chemical Abundances, and Galactic Distributions

TL;DR

This work leverages the HASH PN database and Gaia EDR3 distances to assemble a large, homogeneous sample of 1,449 true Galactic PNe across bulge, thin disk, thick disk, and halo. Using alfa for emission-line fluxes and NEAT for physical conditions and abundances, the study derives reddening, $T_e$, and $N_e$ as well as abundances for He, N, O, Ne, S, Cl, and Ar, compiling 7,200 abundance values from 16,500 lines. The results reveal Gaussian-like distributions of extinction, temperature, and density with medians $c(Hβ) ≈ 1.5$, $T_e ≈ 9,900 ext{ K}$, and $N_e ≈ 1,170 ext{ cm}^{-3}$, and show that thin-disk PNe are generally more enriched while halo PNe are the most metal-poor; a strong S–N correlation ($r = 0.87$) is found among 21 cross-element relationships. The paper provides a comprehensive database and statistical framework that supports testing Galactic chemical-evolution models and PN progenitor scenarios, and sets the stage for future work including Magellanic Cloud PN samples and photoionization-model-based inferences.

Abstract

In this study, we investigate the physical and chemical properties of planetary nebulae (PNe) from the Milky Way Galaxy using the largest number of sources to date, with 1,449 True PNe from the HASH database. Among the Galactic components thin disk, thick disk, halo, and bulge-most PNe are concentrated in the Galactic disk, with a median angular size of 12 arcseconds (0.45 pc), while halo PNe tend to have larger sizes. Physical parameters of whole PNe, extinction coefficent c(Hbeta), electron temperature (Te), and density (Ne) show Gaussian-like distributions with medians of 1.5, 9,900 K, and 1,200 cm(-3), respectively. The abundances of He, N, O, Ne, S, Cl, and Ar in PNe show Gaussian distributions with slight variations across Galactic components. PNe located in thin disk exhibit higher abundances, except for O and Ne, while PNe in halo have the lowest values for all elements. Strong correlations between elements, particularly Sulphur vs. Nitrogen (r=0.87), were identified using statistical tests. Comparisons with previous studies reveal variations ( 2 dex.) in abundance ratios, particularly in halo PNe. We also present the first detailed database in the literature, providing 7,200 abundance values for these elements, derived from 16,500 emission line measurements, to support the testing and development of theoretical models.

Figures (14)

• Figure 1: The flowchart of the study.
• Figure 2: Histograms of angular sizes of PNe in arcseconds (a) and parsecs (b), and morphological classifications based on the ERBIAS (c) and SPARM (d) schemes. The data are sourced from the HASH database 2023MNRAS.519.1049T. Colors indicate the Galactic component associated with each PN: bulge (blue), thin disk (red), thick disk (green), and halo (orange). The black dashed line shows the overall mean value, while the colored dashed lines indicate the median values for each Galactic component.
• Figure 3: Histogram displaying the angular distances between the HASH coordinates and the matched Gaia EDR3 source coordinates for each PNe. The Galactic components are color-coded as follows: bulge (blue), thin disk (red), thick disk (green), and halo (orange).
• Figure 4: The histogram of distances of PNe from the Gaia EDR3 database. The Galactic components are color-coded as follows: bulge (blue), thin disk (red), thick disk (green), and halo (orange).
• Figure 5: Scatter plot illustrating the relationship between Gaia EDR3 geometric distances (Rgeo) and the corresponding parallax values with their uncertainties, shown as vertical error bars. The Galactic components are color-coded as follows: bulge (blue), thin disk (red), thick disk (green), and halo (orange).