Details

Autor(en) / Beteiligte

• Matsumoto, Akinori
• Ouchi, Masami
• Nakajima, Kimihiko
• Kawasaki, Masahiro
• Murai, Kai
• Motohara, Kentaro
• Harikane, Yuichi
• Ono, Yoshiaki
• Kushibiki, Kosuke
• Koyama, Shuhei
• Aoyama, Shohei
• Konishi, Masahiro
• Takahashi, Hidenori
• Isobe, Yuki
• Umeda, Hiroya
• Sugahara, Yuma
• Onodera, Masato
• Nagamine, Kentaro
• Kusakabe, Haruka
• Hirai, Yutaka
• Moriya, Takashi J.
• Shibuya, Takatoshi
• Komiyama, Yutaka
• Fukushima, Keita
• Fujimoto, Seiji
• Hattori, Takashi
• Hayashi, Kohei
• Inoue, Akio K.
• Kikuchihara, Shotaro
• Kojima, Takashi
• Koyama, Yusei
• Lee, Chien-Hsiu
• Mawatari, Ken
• Miyata, Takashi
• Nagao, Tohru
• Ozaki, Shinobu
• Rauch, Michael
• Saito, Tomoki
• Suzuki, Akihiro
• Takeuchi, Tsutomu T.
• Umemura, Masayuki
• Xu, Yi
• Yabe, Kiyoto
• Zhang, Yechi
• Yoshii, Yuzuru

Titel

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

Ist Teil von

• The Astrophysical journal, 2022-12, Vol.941 (2), p.167

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2022

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Abstract 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 (<0.1 Z ⊙ ) galaxies (EMPGs) having reliable He/H measurements with He i λ 10830 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 (0.1–0.4 Z ⊙ ) galaxies with reliable He/H estimates, we obtain Y P = 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 (∼1 σ ) 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 ≳1–2 σ 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 ξ e = 0.05 − 0.02 + 0.03 , N eff = 3.11 − 0.31 + 0.34 , and η × 10 10 = 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 1 σ level, which could mitigate the Hubble tension.