Astrophys. J., 896, 77-77 (2020/June-2)
The PHLEK Survey: a new determination of the primordial helium abundance.
HSYU T., COOKE R.J., PROCHASKA J.X. and BOLTE M.
Abstract (from CDS):
We present Keck NIRSPEC and Keck NIRES spectroscopy of sixteen metal-poor galaxies that have pre-existing optical observations. The near-infrared (NIR) spectroscopy specifically targets the He I λ10830 Å emission line, due to its sensitivity to the physical conditions of the gas in H II regions. We use these NIR observations, combined with optical spectroscopy, to determine the helium abundance of sixteen galaxies across a metallicity range 12+log10(O/H) = 7.13-8.00. This data set is combined with two other samples where metallicity and helium abundance measurements can be secured: star-forming galaxies selected from the Sloan Digital Sky Survey spectroscopic database, and existing low-metallicity systems in the literature. We calculate a linear fit to these measurements, accounting for intrinsic scatter, and report a new determination of the primordial helium number abundance, yP=0.0805–0.0017+0.0017, which corresponds to a primordial helium mass fraction YP=0.2436–0.0040+0.0039. Using our determination of the primordial helium abundance in combination with the latest primordial deuterium measurement, (D/H)P×105=2.527±0.030, we place a bound on the baryon density Ωbh2=0.0215–0.0005+0.0005 and the effective number of neutrino species Neff=2.85–0.25+0.28. These values are in 1.3σ agreement with those deduced from the Planck satellite observations of the temperature fluctuations imprinted on the cosmic microwave background.
© 2020. The American Astronomical Society. All rights reserved.
Dwarf galaxies - Galaxy abundances - Galaxy chemical evolution - big bang nucleosynthesis
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<Available at CDS (J/ApJ/896/77): table2.dat table4.dat table5.dat>
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