Independent Emission and Absorption Abundances for Planetary Nebulae

Abstract

Emission-line abundances have been uncertain for more than a decade due to unexplained discrepancies in the relative intensities of the forbidden lines and weak permitted recombination lines in planetary nebulae (PNe) and H II regions. The observed intensities of forbidden and recombination lines originating from the same parent ion differ from their theoretical values by factors of more than an order of magnitude in some of these nebulae. In this study we observe UV resonance line absorption in the central stars of PNe produced by the nebular gas, and from the same ions that emit optical forbidden lines. We then compare the derived absorption column densities with the emission measures determined from ground-based observations of the nebular forbidden lines. We find for our sample of PNe that the collisionally excited forbidden lines yield column densities that are in basic agreement with the column densities derived for the same ions from the UV absorption lines. A similar comparison involving recombination line column densities produces poorer agreement, although near the limits of the formal uncertainties of the analyses. An additional sample of objects with larger abundance discrepancy factors will need to be studied before a stronger statement can be made that recombination line abundances are not correct.

19 pages, 13 figures, accepted by ApJ. Preprint utilizes emulateapj.cls v. 12/01/06 (included)

References in corpus (12)

• Atomic Data for Permitted Resonance Lines of Atoms and Ions from H to Si, and S, Ar, Ca and Fe
• The Distribution of Thermal Pressures in the Interstellar Medium from a Survey of C I Fine-Structure Excitation
• On the abundance discrepancy problem in HII regions
• Heavy elements in Galactic and Magellanic Cloud HII regions: recombination-line versus forbidden-line abundances
• A deep survey of heavy element lines in planetary nebulae -- II. Recombination line abundances and evidence for ultra-cold plasma
• s-Process Abundances in Planetary Nebulae
• Chemical abundances for Hf 2-2, a planetary nebula with the strongest known heavy element recombination lines
• A Procedure for Correcting the Apparent Optical Depths of Moderately Saturated Interstellar Absorption Lines
• Spatially-Resolved O II Recombination Line Observations of the Ring Nebula, NGC 6720
• Fe II lifetimes and transition probabilities
• Recombination Line vs. Forbidden Line Abundances in Planetary Nebulae
• Comparative Absorption and Emission Abundance Analyses of Nebulae: Ion Emission Densities for IC 418

Cited by in corpus (20)

• Formation of fullerenes in H-containing Planetary Nebulae
• The formation of fullerenes: clues from new C60, C70, and (possible) planar C24 detections in Magellanic Cloud Planetary Nebulae
• Are C60 molecules detectable in circumstellar shells of R Coronae Borealis stars?
• "Counterpart" method for abundance determinations in HII regions
• Physical Properties of Fullerene-containing Galactic Planetary Nebulae
• The High Velocity Gas toward Messier 5: Tracing Feedback Flows in the Inner Galaxy
• Diffuse interstellar bands in fullerene planetary nebulae: the fullerenes - diffuse interstellar bands connection
• Disentangling the metallicity and star formation history of HII galaxies through tailor-made models
• Abundances in planetary nebulae: NGC1535, NGC6629, He2-108, and Tc1
• A search for diffuse bands in fullerene planetary nebulae: evidence of diffuse circumstellar bands
• Atomic data for neutron-capture elements II. Photoionization and recombination properties of low-charge krypton ions
• Excitation of emission lines by fluorescence and recombination in IC418
• A search for hydrogenated fullerenes in fullerene-containing planetary nebulae
• Fullerenes in circumstellar and interstellar environments
• Characterisation of the Planetary Nebula Tc 1 Based on VLT X-Shooter Observations
• Low-ionization structures in planetary nebulae -- II. Densities, temperatures, abundances and excitation of 6 PNe
• HST STIS observations of the mixing layer in the Cat's Eye Nebula
• Detection of the [C I] $\lambda$8727 emission line. Low-ionization structures in NGC 7009
• Detection of C${}_{60}$ Combination Bands in the Near-IR Spectrum of Tc 1
• Connecting high-redshift galaxy populations through observations of local Damped Lyman Alpha dwarf galaxies