Chemical abundances for Hf 2-2, a planetary nebula with the strongest known heavy element recombination lines

Abstract

We present high quality optical spectroscopic observations of the planetary nebula (PN) Hf 2-2. The spectrum exhibits many prominent optical recombination lines (ORLs) from heavy element ions. Analysis of the H {\sc i} and He {\sc i} recombination spectrum yields an electron temperature of $\sim 900$ K, a factor of ten lower than given by the collisionally excited [O {\sc iii}] forbidden lines. The ionic abundances of heavy elements relative to hydrogen derived from ORLs are about a factor of 70 higher than those deduced from collisionally excited lines (CELs) from the same ions, the largest abundance discrepancy factor (adf) ever measured for a PN. By comparing the observed O {\sc ii} $\lambda$4089/$\lambda$4649 ORL ratio to theoretical value as a function of electron temperature, we show that the O {\sc ii} ORLs arise from ionized regions with an electron temperature of only $\sim 630$ K. The current observations thus provide the strongest evidence that the nebula contains another previously unknown component of cold, high metallicity gas, which is too cool to excite any significant optical or UV CELs and is thus invisible via such lines. The existence of such a plasma component in PNe provides a natural solution to the long-standing dichotomy between nebular plasma diagnostics and abundance determinations using CELs on the one hand and ORLs on the other.

arXiv comment12 pages, 5 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

References in corpus (10)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• 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 - I. Observations and forbidden-line densities, temperatures and abundances
• A deep survey of heavy element lines in planetary nebulae -- II. Recombination line abundances and evidence for ultra-cold plasma
• Physical conditions in the planetary nebula Abell 30
• Electron temperatures and densities of planetary nebulae determined from the nebular hydrogen recombination spectrum and temperature and density variations
• VLT Echelle Spectrophotometry of the Planetary Nebula NGC 5307 and Temperature Variations
• Helium recombination spectra as temperature diagnostics for planetary nebulae
• Spatially-Resolved O II Recombination Line Observations of the Ring Nebula, NGC 6720
• Identification and Characterization of Faint Emission Lines in the Spectrum of the Planetary Nebula IC 418

Cited by in corpus (70)

• Understanding Galaxy Evolution through Emission Lines
• On the abundance discrepancy problem in HII regions
• Binary stars as the key to understanding planetary nebulae
• Nebular spectroscopy: A guide on H II regions and planetary nebulae
• Collision Strengths for [O III] Optical and Infrared Lines
• Binarity and the abundance discrepancy problem in planetary nebulae
• The temperature and ionization structure of the emitting gas in HII galaxies: Implications for the accuracy of abundance determinations
• Binary central stars of PN discovered through photometric variability. I. What we know and what we would like to find out
• Confirmation of the link between central star binarity and extreme abundance discrepancy factors in planetary nebulae
• Elemental abundances of Galactic bulge planetary nebulae from optical recombination lines
• A catalogue of integrated H-alpha fluxes for 1,258 Galactic planetary nebulae
• NGC 6778: Strengthening the link between extreme abundance discrepancy factors and central star binarity in planetary nebulae
• The hydrogen-deficient knot of the `born again' planetary nebula Abell 58 (V605 Aql)
• Integral field spectroscopy of planetary nebulae: mapping the line diagnostics and hydrogen-poor zones with VLT FLAMES
• Very deep spectroscopy of the bright Saturn Nebula NGC 7009 -- I. Observations and plasma diagnostics
• Understanding and reducing statistical uncertainties in nebular abundance determinations
• Temperature inhomogeneities cause the abundance discrepancy in H II regions
• Density biases and temperature relations for DESIRED HII regions
• Analysis of chemical abundances in planetary nebulae with [WC] central stars. II. Chemical abundances and the abundance discrepancy factor
• C/O abundance ratios, iron depletions, and infrared dust features in Galactic planetary nebulae
• Analysis of chemical abundances in planetary nebulae with [WC] central stars. I. Line intensities and physical conditions
• Faint recombination lines in Galactic PNe with [WC] nucleus
• The effects of spatially distributed ionisation sources on the temperature structure of HII region
• Imaging the elusive H-poor gas in the high ADF planetary nebula NGC 6778
• New effective recombination coefficients for nebular N II lines
• SALT reveals the barium central star of the planetary nebula Hen 2-39
• Chemical abundances in Galactic planetary nebulae with Spitzer spectra
• MUSE spectroscopy of planetary nebulae with high abundance discrepancies
• Plasma Diagnostics for Planetary Nebulae and H II Regions Using the N II and O II Optical Recombination Lines
• Recombination coefficients for O II lines in nebular conditions
• H I Free-Bound Emission of Planetary Nebulae with Large Abundance Discrepancies: Two-Component Models versus Kappa-distributed electrons
• The planetary nebula IPHASXJ211420.0+434136 (Ou5): insights into common-envelope dynamical and chemical evolution
• Very deep spectroscopy of the bright Saturn Nebula NGC 7009 - II. Analysis of the rich optical recombination spectrum
• IC 4663: The first unambiguous [WN] Wolf-Rayet central star of a planetary nebula
• Chemical Abundances of Planetary Nebulae in the Substructures of M31
• Co-spatial Long-slit UV/Optical Spectra of Ten Galactic Planetary Nebulae with HST/STIS I. Description of the Observations, Global Emission-line Measurements, and CNO Abundances
• Electron Temperatures and Free-Electron Energy Distributions of Nebulae from C II Dielectronic Recombination Lines
• Measuring Chemical Abundances with Infrared Nebular Lines: HII-Chi-mistry-IR
• Excitation of emission lines by fluorescence and recombination in IC418
• An Imaging Spectroscopic Survey of the Planetary Nebula NGC 7009 with MUSE
• The Continuum Emission Spectrum of Hf 2-2 near the Balmer Limit and the ORL versus CEL abundance and temperature Discrepancy
• Independent Emission and Absorption Abundances for Planetary Nebulae
• The Discrepant Kinematics of ORLs and CELs in NGC 7009 as a Function of Ionization Structure
• Very Large Telescope deep echelle spectroscopy of Galactic planetary nebulae NGC 6153, M 1-42 and Hf 2-2
• Properties of the ionized gas in HH202. I: Results from integral field spectroscopy with PMAS
• Can X-rays provide a solution to the abundance discrepancy problem in photoionised nebulae?
• The Kinematics of the Permitted C II $\lambda$ 6578 Line in a Large Sample of Planetary Nebulae
• Small-spatial scale variations of nebular properties and the abundance discrepancy in three Galactic HII regions
• The kinematical behaviour of ORLs and CELs in Galactic PNe
• On the non-thermal kappa-distributed electrons in planetary nebulae and HII regions: the kappa index and its correlations with other nebular properties
• The impact of strong recombination on temperature determination in planetary nebulae
• NGC 6153: Reality is complicated
• Electron Temperatures of Planetary Nebulae Determined from the He I Discontinuities
• A pilot study of the radio-continuum emission from MASH planetary nebulae
• Bi-abundance ionization structure of the Wolf-Rayet planetary nebula PB 8
• Physical conditions and chemical abundances in photoionized nebulae from optical spectra
• Resonant Temperature Fluctuations in Nebulae Ionized by Short-Period Binary Stars
• Planetary Nebulae: What can they tell us about close binary evolution?
• Imaging the elusive H-poor gas in planetary nebulae with large abundance discrepancy factors
• Can the Kappa-distributed electron energies account for the intensity ratios of O II lines in photoionized gaseous nebulae?
• Emission line profiles as a probe of physical conditions in planetary nebulae
• Dissecting the Planetary Nebula NGC 4361 with MUSE
• SDSS-V LVM: Resolving Physical Conditions in the Trifid Nebula
• Realistic Models for Filling and Abundance Discrepancy Factors in Photoionised Nebulae
• Kinematical analysis of PNe with high ADF: Hf 2-2 and M 1-42
• SDSS-V LVM: A spatially resolved study of the physical conditions and the chemical abundance discrepancy in the Lagoon Nebula (M 8)
• Gaseous abundances in planetary nebulae: What have we learned in the past five years?
• The kinematical behavior of ORLs and CELs in PNe with [WC] central star
• Reduce, Reuse, Recycle: Planetary Nebulae as Green Galactic Citizens
• Direct Far-Infrared Metal Abundances (FIRA) I: M101