2026-09-28 カナダ・ブリティッシュコロンビア大学（UBC）
A view of CHIME at night, with the Milky Way in the background. Photo credit: CHIME collaboration.
＜関連情報＞
- https://news.ubc.ca/2026/09/canadian-telescope-maps-earliest-glow-of-hydrogen/
- https://iopscience.iop.org/article/10.3847/1538-4357/ae9835
- https://iopscience.iop.org/article/10.3847/1538-4357/ae9747
カナダ水素強度マッピング実験によるz ∼ 1における宇宙論的21cm信号の自己相関検出 Detection of the Cosmological 21 cm Signal in Autocorrelation at z ∼ 1 with the Canadian Hydrogen Intensity Mapping Experiment
The CHIME Collaboration, Mandana Amiri, Kevin Bandura, Arnab Chakraborty, Jean-François Cliche, Matt Dobbs, Simon Foreman, Liam Gray, Mark Halpern, Alex S Hill,…
The Astrophysical Journal Published: 2026 September 28
DOI:10.3847/1538-4357/ae9835
Abstract
We present the first detection of the cosmological 21 cm intensity mapping signal in autocorrelation at z ∼ 1 with the Canadian Hydrogen Intensity Mapping Experiment (CHIME). Using 94 nights of observation, we have measured the 21 cm auto power spectrum over a frequency range of 608.2–707.8 MHz (z = 1.34–1.01) at 0.4 h Mpc−1 ≲ k ≲ 1.5 h Mpc−1, with a detection significance of 12.4σ. Our analysis employs significant improvements to the CHIME data processing pipeline compared to previous work, including novel radio frequency interference detection and masking algorithms, achromatic beamforming techniques, and foreground filtering before time averaging to minimize spectral leakage. We establish the robustness and reliability of our detection through a comprehensive suite of validation tests. We also measure the 21 cm signal in two independent sub-bands centered at z ∼ 1.08 and z ∼ 1.24 with detection significance of 8.6σ and 9.1σ, respectively. We briefly discuss the theoretical interpretation of these measurements in terms of a power spectrum model, deferring the details to a companion paper. This auto power spectrum detection demonstrates CHIME’s capability to probe large-scale structure through 21 cm intensity mapping without reliance on external galaxy surveys.
カナダ水素強度マッピング実験によるz ∼ 1における21cm自己パワースペクトル測定の解釈 Interpretation of 21 cm Autopower Spectrum Measurement at z ∼ 1 by the Canadian Hydrogen Intensity Mapping Experiment
Mandana Amiri, Kevin Bandura, Arnab Chakraborty, Zhuo Yu Brian Chu, Matt Dobbs, Simon Foreman, Liam Gray, Mark Halpern, Gary Hinshaw, Albin Joseph,…
The Astrophysical Journal Published: 2026 September 28
DOI:10.3847/1538-4357/ae9747
Abstract
Observations with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) have been used to measure the 21 cm intensity mapping autopower spectrum, at z ∼ 1, over a frequency range from 608.2 to 707.8 MHz at wavenumbers 0.4 h Mpc−1 ≲ k ≲ 1.5 h Mpc−1. In this paper, we present the results of two different approaches to interpreting this measurement. In the first approach, we use a parametric power spectrum model to constrain an amplitude parameter, defined asA2HI≡106Ω2H(b2H +＜fμ2＞)2, where ΩHI is the cosmological density parameter for atomic hydrogen (H I), bHI is the linear bias for H I, and 〈fμ2〉 incorporates the dominant large-scale impact of redshift-space distortions on the angle-averaged power spectrum. Imposing an additional prior on either ΩHI or bHI, based on values in the literature, allows us to break the pairwise degeneracy between those two parameters. In the second approach, we compare CHIME’s measurement with predictions for the power spectrum of H I from the IllustrisTNG simulations, finding that the measurement disagrees with the TNG100 run at 3.1σ and the TNG300 run at 4.0σ. The disagreement is likely attributable to the effects of nonlinear H I clustering and redshift-space distortions in the simulations, rather than the total abundance of H I, and invites further investigation of the physical processes in the simulations that determine the behavior of H I at nonlinear scales. These results exemplify the ability of 21 cm intensity mapping to provide astrophysical information using measurements at nonlinear scales.
