The Primordial Abundance of 4He: A Self-consistent Empirical Analysis of Systematic Effects in a Large Sample of Low-Metallicity H II Regions
By Y. Izotov, T. Thuan, G. Stasińska. 2007
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We determine the primordial helium mass fraction Yp using 93 spectra of 86 low-metallicity extragalactic H II regions. This sample constitutes the largest and most homogeneous high-quality data set in existence for the determination of Yp. For comparison, and to improve the statistics in our investigation of systematic effects affecting the Yp determination, we have also considered a sample of 271 low-metallicity H II regions selected from Data Release 5 of the Sloan Digital Sky Survey. Although this larger sample shows more scatter, it gives results that are consistent at the 2 σ level with our original sample. We have considered known systematic effects that may affect the 4He abundance determination. They include different sets of He I line emissivities and reddening laws, collisional and fluorescent enhancements of He I recombination lines, underlying He I stellar absorption lines, collisional excitation of hydrogen lines, temperature and ionization structure of the H II region, and deviation of He I and H emission-line intensities from case B. However, the most likely value of Yp depends on the adopted set of He I line emissivities. Using Monte Carlo methods to solve simultaneously the above systematic effects, we find a primordial helium mass fraction of Yp = 0.2472 ± 0.0012 when using the He I emissivities from Benjamin and coworkers and 0.2516 ± 0.0011 when using those from Porter and coworkers. The first value agrees well with the value given by standard big bang nucleosynthesis (SBBN) theory, while the value obtained with the likely more accurate emissivities of Porter and coworkers is higher at the 2 σ level. This latter value, if confirmed, would imply slight deviations from SBBN.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/47897e500c454697e901c83f65e1e8a69c696147
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In Astronomy and Astrophysics
- M. Zaldarriaga
- David N. Spergel
- Simon D. M. White
- Mark Halpern
- Andrey V. Kravtsov
- L. Hernquist
- Volker Springel
- J. Dunkley
Citations in the corpus
- A new determination of the primordial He abundance using the He i λ10830 Å emission line: cosmological implications (2014, methodology): “Using a restricted subsample of 22 objects selected from the same HeBCD sample of Izotov et al. (2007), Aver et al. (2012) derived a value Yp = 0.2534 ± 0.0083.”
- A new approach to systematic uncertainties and self-consistency in helium abundance determinations (2010, methodology): “However, correcting for the effects of underlying He I absorption is not straightforward (see discussions in Olive & Skillman 2001; Izotov et al. 2007).”
- THE PRIMORDIAL ABUNDANCE OF 4He: EVIDENCE FOR NON-STANDARD BIG BANG NUCLEOSYNTHESIS (2010, methodology): “These slopes are shallower than the ones of 4.33±0.75 and 2.85±0.49 derived by Izotov et al. (2007).”
- THE ATACAMA COSMOLOGY TELESCOPE: COSMOLOGICAL PARAMETERS FROM THE 2008 POWER SPECTRUM (2010, background): “…abundance estimated from observations of metal poor extragalactic regions (see Steigman 2007; Peimbert 2008, for example) is YP = 0.252 ± 0.004 and 0.252±0.001 (Izotov et al. 2007), although a higher measurement of YP = 0.2565±0.0010(stat)±0.0050(syst) has recently been made (Izotov & Thuan 2010).”
- CONSTRAINTS ON COSMOLOGY FROM THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM OF THE 2500 deg2 SPT-SZ SURVEY (2012, background): “…with DA and allows the CMB data to constrain Yp independently of BBN. Precise experimental inferences of Yp have come from spectral observations of extragalactic clouds of lowmetallicity ionized gas (Izotov et al. 2007; Peimbert et al. 2007; Izotov & Thuan 2010; Aver et al. 2010, 2011, 2012).”
- A MEASUREMENT OF THE DAMPING TAIL OF THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM WITH THE SOUTH POLE TELESCOPE (2011, background): “The primordial 4He abundance may also be inferred from observations of low-metallicity extragalactic HII regions (Izotov et al. 2007; Peimbert et al. 2007; Izotov & Thuan 2010; Aver et al. 2010, 2011).”