We propose MOIRCS Y-band spectroscopy for local extremely metal-poor galaxies (EMPGs) to determine the primordial 4He abundance YP, completing the Subaru intensive program (IP) observations, unfortunately only 45% of which were conducted due to the weather, volcano smoke, and earthquake aftermath. The determination of YP is key to testing the standard cosmology via the effective number of neutrino species Neff, while the Planck constraint is not strong enough. Metal poor galaxies are powerful probes to derive YP. The IP has increased the number of EMPGs with 0.01−0.1 Z⊙, and measured YP with the uncertainty Δ Yp=0.0035 dominated by a statistical error (a total systematic error of <∼ 20%). The IP finds that the Neff calculated from the YP value shows a 2σ tension with the standard model (Neff=3.046) suggesting the existence of new physics such as the lepton asymmetry, while the statistical significance is not high enough to conclude. This MOIRCS program will measure flux ratios of Hei10830 to Pγ lines for 21 EMPGs, and obtain He/H abundance ratios for YP in conjunction with the existing optical spectroscopic data. We will accomplish the accuracy of Δ Yp=0.0022 (Δ Neff ≃ 0.15), testing the early suggestion at the >3σ level.
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