EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension
EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension
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DOI：
10.3847/1538-4357/ac9ea1
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发表时间：
2022-03
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通讯作者：
A. Matsumoto;M. Ouchi;K. Nakajima;M. Kawasaki;Kai Murai;K. Motohara;Y. Harikane;Y. Ono;Kosuke Kushibiki;S. Koyama;S. Aoyama;M. Konishi;H. Takahashi;Y. Isobe;Hiroya Umeda;Y. Sugahara;M. Onodera;K. Nagamine;H. Kusakabe;Y. Hirai;T. Moriya;T. Shibuya;Y. Komiyama;Keita Fukushima;S. Fujimoto;T. Hattori;Kohei Hayashi;A. Inoue;Shotaro Kikuchihara;Takashi Kojima;Y. Koyama;Chien-Hsiu Lee;K. Mawatari;T. Miyata;T. Nagao;S. Ozaki;M. Rauch;Tomoki Saito;A. Suzuki;T. Takeuchi;M. Umemura;Yi Xu;K. Yabe;Yechi Zhang;Y. Yoshii
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作者：
A. Matsumoto;M. Ouchi;K. Nakajima;M. Kawasaki;Kai Murai;K. Motohara;Y. Harikane;Y. Ono;Kosuke Kushibiki;S. Koyama;S. Aoyama;M. Konishi;H. Takahashi;Y. Isobe;Hiroya Umeda;Y. Sugahara;M. Onodera;K. Nagamine;H. Kusakabe;Y. Hirai;T. Moriya;T. Shibuya;Y. Komiyama;Keita Fukushima;S. Fujimoto;T. Hattori;Kohei Hayashi;A. Inoue;Shotaro Kikuchihara;Takashi Kojima;Y. Koyama;Chien-Hsiu Lee;K. Mawatari;T. Miyata;T. Nagao;S. Ozaki;M. Rauch;Tomoki Saito;A. Suzuki;T. Takeuchi;M. Umemura;Yi Xu;K. Yabe;Yechi Zhang;Y. Yoshii
原始He丰度Y P是宇宙学的有力探针。目前，Y P最好通过对贫金属星系的观测来确定，而只有少数已知的局部极贫金属（<0.1Z）星系（EMPG）具有可靠的He/H测量，He i λ10830近红外（NIR）发射。在这里，我们提出了深斯巴鲁近红外光谱的10个EMPG。结合已有的光学数据，用马尔可夫链蒙特卡罗算法可靠地计算了10个EMPG中5个的He/H值。将现有的3个EMPG和51个中等贫金属（0.1-0.4Z）星系与可靠的He/H估计相加，在（He/H）-（O/H）平面上通过线性回归得到YP=0.2370−0.0034+0.0033，其中我们将EMPG的数量从3个增加到8个，锚定星系中最贫金属的气体He/H。虽然我们的Y P测量和以前的测量是一致的，但由于我们的EMPG，我们的结果略小（Δ 1σ）。包括现有的原始氘D P测量，我们约束中微子物种的有效数量N eff和重子-光子比η，显示标准模型和普朗克合作等（2020）的<$1 -2σ张力。受张力的影响，我们允许电子中微子的简并度参数Ee以及Neff和η变化。我们从普朗克合作组的Y P和D P测量中得到了ε e=0.05−0.02+0.03，Neff=3.11−0.31+0.34，η×1010=6.08−0.06+0.06。我们的约束表明轻子不对称性，并允许在1σ水平内有较高的Neff值，这可以减轻哈勃张力。
The primordial He abundance Y P is a powerful probe of cosmology. Currently, Y P is best determined by observations of metal-poor galaxies, while there are only a few known local extremely metal-poor (<0.1Z ⊙) galaxies (EMPGs) having reliable He/H measurements with He i λ10830 near-infrared (NIR) emission. Here we present deep Subaru NIR spectroscopy for 10 EMPGs. Combining the existing optical data, He/H values of 5 out of the 10 EMPGs are reliably derived by the Markov chain Monte Carlo algorithm. Adding the existing 3 EMPGs and 51 moderately metal-poor (0.1–0.4Z ⊙) galaxies with reliable He/H estimates, we obtain YP=0.2370−0.0034+0.0033 by linear regression in the (He/H) − (O/H) plane, where we increase the number of EMPGs from three to eight anchoring He/H of the most metal-poor gas in galaxies. Although our Y P measurement and previous measurements are consistent, our result is slightly (∼1σ) smaller due to our EMPGs. Including the existing primordial deuterium D P measurement, we constrain the effective number of neutrino species N eff and the baryon-to-photon ratio η showing ≳1–2σ tensions with the Standard Model and Planck Collaboration et al. (2020). Motivated by the tensions, we allow the degeneracy parameter of the electron neutrino ξ e , as well as N eff and η, to vary. We obtain ξe=0.05−0.02+0.03 , Neff=3.11−0.31+0.34 , and η×1010=6.08−0.06+0.06 from the Y P and D P measurements with a prior of η taken from Planck Collaboration et al. Our constraints suggest a lepton asymmetry and allow for a high value of N eff within the 1σ level, which could mitigate the Hubble tension.