宇宙の膨張速度を正確に測定~現在の膨張速度は新たな謎を示唆~

2025-12-05 東京大学

東京大学大学院理学系研究科附属ビッグバン宇宙国際研究センターを含むTDCOSMO共同研究チームは、重力レンズ効果で複数像となったクエーサー8天体の時間遅延を解析し、ハッブル定数H₀をこれまでで最も高精度に測定した。JWST・HST・ケック望遠鏡・VLTなどによる高分解能観測と、レンズ銀河の分光観測から質量分布を精密にモデル化することで、他の距離較正に依存しない独立な値を得た。その結果、H₀は後期宇宙の測定(約73 km/s/Mpc)と整合的な「速い膨張」を支持し、一方で初期宇宙のCMB観測が示す約67 km/s/Mpc とは統計的に矛盾することが明確になった。これはハッブルテンションが単なる測定誤差ではなく実在する可能性を強く示し、未知の素粒子や初期ダークエネルギーなど標準宇宙モデルを超える新たな物理の存在を示唆する。今後は精度1.5%を目指し、宇宙膨張史の決定的解明を図る。

宇宙の膨張速度を正確に測定~現在の膨張速度は新たな謎を示唆~
TDCOSMO 2025 サンプルに含まれる8つの重力レンズクエーサー
(クレジット:TDCOSMO Collaboration et al. 2025, A&A, in press)

<関連情報>

TDCOSMO 2025: 強い重力レンズ効果による時間遅延からの宇宙論的制約 TDCOSMO 2025: Cosmological constraints from strong lensing time delays

TDCOSMO Collaboration:Simon Birrer, Elizabeth J. Buckley-Geer, Michele Cappellari, Frédéric Courbin, Frédéric Dux, Christopher D. Fassnacht, Joshua A. Frieman, Aymeric Galan, Daniel Gilman, Xiang-Yu Huang, Shawn Knabel, Danial Langeroodi, Huan Lin, Martin Millon, Takahiro Morishita, Veronica Motta, Pritom Mozumdar, Eric Paic, Anowar J. Shajib, William Sheu, Dominique Sluse, Alessandro Sonnenfeld, Chiara Spiniello, Massimo Stiavelli, Sherry H. Suyu,, Chin Yi Tan, Tommaso Treu, Lyne Van de Vyvere, Han Wang, Patrick Wells, Devon M. Williams and Kenneth C. Wong
Astronomy & Astrophysics  Published: 05 December 2025
DOI:https://doi.org/10.1051/0004-6361/202555801

Abstract

We present cosmological constraints from eight strongly lensed quasars (hereafter, the TDCOSMO-2025 sample). Building on previous work, our analysis incorporated new deflector stellar velocity dispersions measured from spectra obtained with the James Webb Space Telescope (JWST), the Keck Telescopes, and the Very Large Telescope (VLT), utilizing improved methods. We used integrated JWST stellar kinematics for five lenses, VLT-MUSE for 2, and resolved kinematics from Keck and JWST for RX J1131−1231. We also considered two samples of non-time-delay lenses: 11 from the Sloan Lens ACS (SLACS) sample with Keck-KCWI resolved kinematics; and four from the Strong Lenses in the Legacy Survey (SL2S) sample. We improved our analysis of line-of-sight effects, the surface brightness profile of the lens galaxies, and orbital anisotropy, and corrected for projection effects in the dynamics. Our uncertainties are maximally conservative by accounting for the mass-sheet degeneracy in the deflectors’ mass density profiles. The analysis was blinded to prevent experimenter bias. Our primary result is based on the TDCOSMO-2025 sample, in combination with Ωm constraints from the Pantheon+ Type Ia supernovae (SN) dataset. In the flat Λ cold dark matter (CDM), we find H0 = 71.6+3.9−3.3 km s−1 Mpc−1. The SLACS and SL2S samples are in excellent agreement with the TDCOSMO-2025 sample, improving the precision on H0 in flat ΛCDM to 4.6%. Using the Dark Energy Survey SN Year-5 dataset (DES-SN5YR) or DESI-DR2 baryonic acoustic oscillations (BAO) likelihoods instead of Pantheon+ yields very similar results. We also present constraints in the open ΛCDM, wCDM, w0waCDM, and wϕCDM cosmologies. The TDCOSMO H0 inference is robust and consistent across all presented cosmological models, and our cosmological constraints in them agree with those from the BAO and SN.

1701物理及び化学
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