Detection of the Cosmological 21 cm Signal in Autocorrelation at z ∼ 1 with the Canadian Hydrogen Intensity Mapping Experiment

@article{amiri2026detection,
  title = {{Detection of the Cosmological 21 cm Signal in Autocorrelation at z ∼ 1 with the Canadian Hydrogen Intensity Mapping Experiment}},
  author = {Mandana Amiri and Kevin Bandura and Arnab Chakraborty and Jean-François Cliche and M. Dobbs and Simon Foreman and Liam Gray and M. Halpern and Alex S. Hill and Gary F. Hinshaw and C. Höfer and Albin Joseph and Nolan Kruger and T. L. Landecker and Rik van Lieshout and Joshua MacEachern and Kiyoshi Wesley Masui and Juan Mena-Parra and Kyle Miller and Nikola Milutinović and Arash Mirhosseini and Laura B. Newburgh and Anna Ordog and Ue‐Li Pen and Tristan Pinsonneault-Marotte and Alex Reda and Andre Renard and Kana Sakaguri and J. Richard Shaw and Shabbir Shaikh and Seth R. Siegel and Saurabh Singh and David Spear and Yukari Uchibori and K. Vanderlinde and Haochen Wang and Donald V. Wiebe and Dallas Wulf},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = sep,
  doi = {10.3847/1538-4357/ae9835},
  url = {https://doi.org/10.3847/1538-4357/ae9835},
  note = {CC BY},
}

TY  - JOUR
TI  - Detection of the Cosmological 21 cm Signal in Autocorrelation at z ∼ 1 with the Canadian Hydrogen Intensity Mapping Experiment
AU  - Mandana Amiri
AU  - Kevin Bandura
AU  - Arnab Chakraborty
AU  - Jean-François Cliche
AU  - M. Dobbs
AU  - Simon Foreman
AU  - Liam Gray
AU  - M. Halpern
AU  - Alex S. Hill
AU  - Gary F. Hinshaw
AU  - C. Höfer
AU  - Albin Joseph
AU  - Nolan Kruger
AU  - T. L. Landecker
AU  - Rik van Lieshout
AU  - Joshua MacEachern
AU  - Kiyoshi Wesley Masui
AU  - Juan Mena-Parra
AU  - Kyle Miller
AU  - Nikola Milutinović
AU  - Arash Mirhosseini
AU  - Laura B. Newburgh
AU  - Anna Ordog
AU  - Ue‐Li Pen
AU  - Tristan Pinsonneault-Marotte
AU  - Alex Reda
AU  - Andre Renard
AU  - Kana Sakaguri
AU  - J. Richard Shaw
AU  - Shabbir Shaikh
AU  - Seth R. Siegel
AU  - Saurabh Singh
AU  - David Spear
AU  - Yukari Uchibori
AU  - K. Vanderlinde
AU  - Haochen Wang
AU  - Donald V. Wiebe
AU  - Dallas Wulf
PY  - 2026
DA  - 2026/09/28
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/ae9835
UR  - https://doi.org/10.3847/1538-4357/ae9835
AB  - 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 12.4 σ . 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 8.6 σ and 9.1 σ , 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.
SN  - 0004-637X
SN  - 1538-4357
ER  -