南極点望遠鏡、遠方宇宙の物質のこれまでで最も鮮明な地図を公開（South Pole Telescope releases clearest map ever of matter in the distant universe）

2026-09-03 シカゴ大学（UChicago）

シカゴ大学の南極望遠鏡（SPT）を用いた国際研究チームは、宇宙における暗黒物質などの物質分布を、これまでで最も高精度に可視化した地図を公開した。南極望遠鏡で観測した宇宙マイクロ波背景放射（CMB）の微細な変化を利用し、遠方の銀河や銀河団などを含む物質が重力によって光の進路を曲げる「重力レンズ効果」を測定した。これにより、約100億年前から現在までの宇宙に存在する物質の分布を約1,000平方度にわたってマッピングし、従来より高い解像度で暗黒物質の構造を捉えた。研究ではSPTの高感度観測に加え、欧州宇宙機関（ESA）のPlanck衛星などのデータも組み合わせ、CMB偏光を含む情報から物質分布を再構成した。この地図は、宇宙の構造形成や暗黒物質の性質、宇宙膨張を支配する暗黒エネルギーを検証するための重要なデータとなる。特に、物質が現在どの程度まとまっているかを示す観測値と標準宇宙論モデルとの比較を通じ、宇宙論に残る不一致の原因を探る手掛かりになると期待されている。

Gravitational lensing occurs when the enormous gravity of galaxies bends passing rays of light, which shows up in characteristic half-moon shapes (as in the above image, taken by the Hubble Space Telescope).Image courtesy ESA/Hubble & NASA, S. Jha.

＜関連情報＞

SPT-3G D1: 二次推定器によるCMBレンズ再構成と宇宙論
SPT-3G D1: Quadratic-Estimator CMB Lensing Reconstruction and Cosmology

Y. Omori, W. L. K. Wu, Y. Nakato, F. Bianchini, L. Balkenhol, C. Daley, W. Quan, E. Anderes, A. J. Anderson, B. Ansarinejad, M. Archipley, D. R. Barron, P. S. Barry, K. Benabed, A. N. Bender, B. A. Benson, L. E. Bleem, S. Bocquet, F. R. Bouchet, E. Camphuis, M. G. Campitiello, J. E. Carlstrom, J. Carron, C. L. Chang, P. M. Chichura, A. Chokshi, T.-L. Chou, A. Coerver, T. M. Crawford, T. de Haan, K. R. Dibert, M. A. Dobbs, M. Doohan, D. Dutcher, C. Feng, K. R. Ferguson, N. C. Ferree, K. Fichman, A. Foster, S. Galli, A. E. Gambrel, A. K. Gao, F. Ge, F. Guidi, S. Guns, N. W. Halverson, E. Hivon, G. P. Holder, W. L. Holzapfel, J. C. Hood, A. Hryciuk, N. Huang, T. Jhaveri, F. Kéruzoré, A. R. Khalife, L. Knox, K. Kornoelje, C.-L. Kuo, K. Levy, Y. Li, A. E. Lowitz, C. Lu, G. P. Lynch, T. J. Maccarone, A. S. Maniyar, E. S. Martsen, F. Menanteau, M. Millea, J. Montgomery, T. Natoli, A. Ouellette, Z. Pan, P. Paschos, K. A. Phadke, A. W. Pollak, K. Prabhu, M. Rahimi, A. Rahlin, C. L. Reichardt, M. Rouble, J. E. Ruhl, A. C. Silva Oliveira, A. Simpson, J. A. Sobrin, A. A. Stark, J. Stephen, C. Tandoi, C. Trendafilova, J. D. Vieira, A. G. Vieregg, A. Vitrier, Y. Wan, N. Whitehorn, M. R. Young, J. A. Zebrowski
arXiv Submitted on 31 Aug 2026
DOI:https://doi.org/10.48550/arXiv.2608.31136

We present a map of the cosmic microwave background (CMB) lensing potential reconstructed from observations taken during the 2019 and 2020 seasons with the third-generation camera on the South Pole Telescope (SPT), covering the 1500deg² SPT-3G Main field, referred to as the SPT-3G D1 dataset. From the multi-frequency temperature and polarization data, we reconstruct the CMB lensing field using a quadratic estimator that jointly accounts for the T, E, and B fields and their covariance. The resulting lensing map is dominated by polarization information for L≲600 and provides the highest signal-to-noise measurement per mode reported to date. With nuisance parameters fixed to their best-fit values, we measure a lensing amplitude consistent with unity at 2% precision relative to the ΛCDM model that best fits the combined Planck, ACT DR6, and SPT-3G D1 TT/TE/EE likelihoods (CMB_SPA). We further measure the structure-growth parameter σ8Ω^0.25_m to be 0.6046±0.0096 from the SPT-3G D1 lensing spectrum alone and 0.6020±0.0084 when combined with ACT DR6 and Planck PR4 CMB lensing. By further combining this with CMB_SPA and the latest DESI DR2 BAO data, we obtain ∑m_ν<0.072eV (95% C.L.) when allowing the neutrino mass to vary within ΛCDM. Compared with previous work, the better agreement of our measurement with DESI DR2 BAO yields both this relaxed upper bound and reduced (∼2σ) preferences for nonzero spatial curvature and for deviations of (w₀,w_a) from the ΛCDM expectation. When we combine CMB lensing with the DES Y3 3×2pt analysis, we obtain S₈=0.811±0.011, corresponding to a 1.4% constraint on the late-time clustering amplitude. This precision is competitive with that obtained from the primary CMB within ΛCDM.