He~I Emission in the Orion Nebula and Implications for Primordial Helium Abundance

Abstract

We apply a recently developed theoretical model of helium emission to observations of both the Orion Nebula and a sample of extragalactic H II regions. In the Orion analysis, we eliminate some weak and blended lines and compare theory and observation for our reduced line list. With our best theoretical model we find an average difference between theoretical and observed intensities $<I_{predicted}/I_{observed}-1>=6.5$. We argue that both the red and blue ends of the spectrum may have been inadequately corrected for reddening. For the 22 highest quality lines, with $3499\mathring{A}\le \lambda \le 6678\mathring{A}$, our best model predicts observations to an average of 3.8%. We also perform an analysis of the reported observational errors and conclude they have been underestimated. In the extragalactic analysis, we demonstrate the likelihood of a large systematic error in the reported data and discuss possible causes. This systematic error is at least as large as the errors associated with nearly all attempts to calculate the primordial helium abundance from such observations. Our Orion analysis suggests that the problem does not lie in the theoretical models. We demonstrate a correlation between equivalent width and apparent helium abundance of lines from extragalactic sources that is most likely due to underlying stellar absorption. Finally, we present fits to collisionless case-B He I emissivities as well as the relative contributions due to collisional excitations out of the metastable $2s{}^{3}S$ term.

arXiv commentaccepted for publication in ApJ

References in corpus (16)

• The Origin of the Mass--Metallicity Relation: Insights from 53,000 Star-Forming Galaxies in the SDSS
• Systematic effects and a new determination of the primordial abundance of 4He and dY/dZ from observations of blue compact galaxies
• A reappraisal of the chemical composition of the Orion nebula based on VLT echelle spectrophotometry
• Improving Predictions for Helium Emission Lines
• A Realistic Determination of the Error on the Primordial Helium Abundance: Steps Toward Non-Parametric Nebular Helium Abundances
• Precision Cosmology? Not Just Yet
• Synthetic spectra of H Balmer and HeI absorption lines. II: Evolutionary synthesis models for starburst and post-starburst galaxies
• Temperature Bias and the Primordial Helium Abundance Determination
• Grain size distributions and photo-electric heating in ionized media
• Theoretical He I Emissivities in the Case B Approximation
• Primordial Helium Abundance: A Reanalysis of the Izotov-Thuan Spectroscopic Sample
• Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies. III. SBS 1415+437
• The He abundance in the metal-deficient blue compact dwarf galaxies Tol 1214-277 and Tol 65
• Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies. II. HS 1442+4250
• Deviations from He I Case B Recombination Theory and Extinction Corrections in the Orion Nebula
• J-resolved He I emission predictions in the low-density limit

Cited by in corpus (53)

• Primordial Nucleosynthesis: from precision cosmology to fundamental physics
• The effects of He I 10830 on helium abundance determinations
• Extragalactic chemical abundances: do HII regions and young stars tell the same story? The case of the spiral galaxy NGC 300
• Revised Primordial Helium Abundance Based on New Atomic Data
• The primordial abundance of 4He: a self-consistent empirical analysis of systematic effects in a large sample of low-metallicity HII regions
• Big Bang Nucleosynthesis and Particle Dark Matter
• Keck HIRES Spectroscopy of Extragalactic HII Regions: C and O Abundances from Recombination Lines
• A New Approach to Systematic Uncertainties and Self-Consistency in Helium Abundance Determinations
• ALFALFA Discovery of the Nearby Gas-Rich Dwarf Galaxy Leo~P. III. An Extremely Metal Deficient Galaxy
• The primordial helium abundance from updated emissivities
• Neutrinos And Big Bang Nucleosynthesis
• Chemical abundances in M31 from HII regions
• Improved He I Emissivities in the Case B Approximation
• Properties of the ionized gas in HH202. II: Results from echelle spectrophotometry with UVES
• Improving Helium Abundance Determinations with Leo P as a Case Study
• NGC 2579 and the carbon and oxygen abundance gradients beyond the solar circle
• Primordial 4He abundance: a determination based on the largest sample of HII regions with a methodology tested on model HII regions
• The Impact of Recent Advances in Laboratory Astrophysics on our Understanding of the Cosmos
• Planetary nebulae in the direction of the Galactic bulge: On nebulae with emission-line central stars
• Analysis of chemical abundances in planetary nebulae with [WC] central stars. II. Chemical abundances and the abundance discrepancy factor
• Mapping systematic errors in helium abundance determinations using Markov Chain Monte Carlo
• A Bayesian direct method implementation to fit emission line spectra: Application to the primordial He abundance determination
• Planetary nebulae and HII regions in the spiral galaxy NGC 300. Clues on the evolution of abundance gradients and on AGB nucleosynthesis
• Faint recombination lines in Galactic PNe with [WC] nucleus
• Planetary nebulae in M33: probes of AGB nucleosynthesis and ISM abundances
• The ionized gas at the center of IC 10: A possible localized chemical pollution by Wolf-Rayet stars
• Revisiting He-like X-ray Emission Line Plasma Diagnostics
• The chemical composition of planetary nebulae and HII regions in NGC 3109
• SALT reveals the barium central star of the planetary nebula Hen 2-39
• Analysis of two SMC HII Regions Considering Thermal Inhomogeneities: Implications for the Determinations of Extragalactic Chemical Abundances
• Three-dimensional chemically homogeneous and bi-abundance photoionization models of the "super-metal-rich" planetary nebula NGC 6153
• Uncertainties in Theoretical HeI Emissivities: HII Regions, Primordial Abundance, and Cosmological Recombination
• Chemical behavior of the Dwarf Irregular Galaxy NGC 6822. Its PN and HII region abundances
• A global study of the HII region M43 and its ionizing star (I. Stellar parameters and nebular empirical analysis)
• Photoionized Herbig-Haro objects in the Orion Nebula through deep high-spectral resolution spectroscopy I: HH529II and III
• Resolved Star Formation on Sub-galactic Scales in a Merger at z=1.7
• Ionized gas diagnostics from protoplanetary discs in the Orion Nebula and the abundance discrepancy problem
• IC 4663: The first unambiguous [WN] Wolf-Rayet central star of a planetary nebula
• NLTE Model of NGC 6543's Central Star and its Relation with the Surrounding Planetary Nebula
• A classification of HII regions based on Oxygen and Helium lines: The cases of TOL2146-391 and TOL0357-3915
• H, He-like recombination spectra I: $l$-changing collisions for hydrogen
• Helium line emissivities for nebular astrophysics
• Cosmic Chemical Evolution with an Early Population of Intermediate Mass Stars
• HeI in the central Giant HII Region of NGC 5253. A 2D observational approach to collisional and radiative transfer effects
• Outside-in stellar formation in the spiral galaxy M33?
• The extinction properties of long GRB host galaxies from H and He I recombination lines
• M1-78: a nitrogen-rich Galactic compact HII region beyond the Perseus arm
• Measurements of 4He in Metal-Poor Extragalactic HII Regions: the Primordial Helium Abundance and the Delta Y / Delta O Ratio
• The Primordial Helium Abundance
• Reduce, Reuse, Recycle: Planetary Nebulae as Green Galactic Citizens
• Atomic Processes in Planetary Nebulae and H II Regions
• From primordial ${}^4$He abundance to the Higgs field
• H-, He-like recombination spectra -- V: On the dependence of the simulated line intensities on the number of electronic levels of the atoms