初期宇宙の重要な測定値を過去最高の精度で特定（Researchers Pinpoint Key Early-Universe Measurement with Record Precision）

2026-09-09 ミネソタ大学

The research team focused on 15 of the most “pristine” small, remote galaxies ever discovered for these papers. Image provided by NASA

＜関連情報＞

• https://cse.umn.edu/college/news/researchers-pinpoint-key-early-universe-measurement-record-precision
• https://iopscience.iop.org/article/10.3847/1538-4357/ae879f

LBT Y pプロジェクト。I. 原始ヘリウム存在量の改良された決定 ― プロジェクト概要、サンプル選択、観測、および方法論 The LBT Yp Project. I. An Improved Determination of the Primordial Helium Abundance—Project Description, Sample Selection, Observations, and Methodology

Evan D. Skillman, Richard W. Pogge, Erik Aver, Noah S. J. Rogers, Miqaela K. Weller, Keith A. Olive, Danielle A. Berg, John J. Salzer, John H. Miller Jr., Jayde Spiegel,…
The Astrophysical Journal  Published: 2026 September 9
DOI:10.3847/1538-4357/ae879f

Abstract

Extremely low-metallicity H ii regions have been observed with the goal of determining the primordial helium abundance (Y_p). Y_p, combined with standard Big Bang nucleosynthesis and the half-life of the neutron, provides a direct measurement of the number of neutrino families, but Y_p must be measured very precisely to provide meaningful constraints on physics beyond the Standard Model. Here we describe a program to combine new Large Binocular Telescope (LBT) observations with a new analysis methodology to significantly improve the determination of Y_p. The LBT, with its MODS and LUCI instruments, produces spectra, which, when combined with our new analysis methodology, are capable of delivering He abundances in individual H ii regions with uncertainties of approximately 2% or less. Archival LBT/MODS spectra of standard stars over a 4 yr period enable the determination of a wavelength-dependent uncertainty in the MODS spectral response, resulting in improved relative emission line uncertainties. An optimized sample of low-metallicity galaxies has been selected with the goal of producing a determination of Y_p with a precision of ∼0.5%, sufficient to provide an independent constraint on the effective number of neutrino families of ∼3%.