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The 21-cm forest as a simultaneous probe of dark matter and cosmic heating history

Nature Astronomy volume 7, pages 1116–1126 (2023)Cite this article

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Abstract

The absorption features in spectra of high-redshift background radio sources, caused by hyperfine structure lines of hydrogen atoms in the intervening structures, are known collectively as the 21-cm forest. They provide a unique probe of small-scale structures during the epoch of reionization, and can be used to constrain the properties of the dark matter (DM) thought to govern small-scale structure formation. However, the signals are easily suppressed by heating processes that are degenerate with a warm DM model. Here we propose a probe of both the DM particle mass and the heating history of the Universe, using the one-dimensional power spectrum of the 21-cm forest. The one-dimensional power spectrum measurement not only breaks the DM model degeneracy but also increases the sensitivity, making the probe actually feasible. Making 21-cm forest observations with the upcoming Square Kilometre Array has the potential to simultaneously determine both the DM particle mass and the heating level in the early Universe, shedding light on the nature of DM and the first galaxies.

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Fig. 1: Synthetic spectra for an unheated IGM.
Fig. 2: Synthetic spectra for the CDM model.
Fig. 3: The expected 1D power spectrum of the 21-cm forest with S150 = 10 mJy.
Fig. 4: The expected 1D power spectrum of the 21-cm forest for different heating histories and different DM models.
Fig. 5: The amplitude and slope of the 1D power spectrum of the 21-cm forest.
Fig. 6: Constraints on TK and mWDM with the 1D power spectrum of the 21-cm forest with S150 = 10 mJy.

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Data availability

The main data that support the results in this work are provided with this paper, and are also available at https://doi.org/10.57760/sciencedb.08093. Further datasets are available from the corresponding authors upon reasonable request. Source data are provided with this paper.

Code availability

The code 21cmFAST used for large-scale simulation is publicly available at https://github.com/andreimesinger/21cmFAST, the codes for simulating small-scale structures and 21-cm forest signals are available from the corresponding authors upon reasonable request, and the GADGET code is available at https://wwwmpa.mpa-garching.mpg.de/gadget.

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Acknowledgements

We thank Y. Li, P.-J. Wu, J.-Z. Qi and B. Yue for helpful discussions. This work was supported by National Key R&D Program of China (grant no. 2022YFF0504300), the National Natural Science Foundation of China (grant nos. 11973047, 11975072, 11835009, 11988101 and 12022306) and the National SKA Program of China (grant nos. 2020SKA0110401, 2020SKA0110100, 2022SKA0110200 and 2022SKA0110203). Y.X. and X.C. also acknowledge support by the CAS grant (grant no. ZDKYYQ20200008). Y.W. acknowledges support by the CAS Interdisciplinary Innovation Team (grant no. JCTD-2019-05). R.L. acknowledges support by the CAS grant (grant no. YSBR-062) and the grant from K.C.Wong Education Foundation.

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Authors and Affiliations

  1. Key Laboratory of Cosmology and Astrophysics (Liaoning) and College of Sciences, Northeastern University, Shenyang, China

    Yue Shao, Xin Zhang & Xuelei Chen

  2. National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China

    Yidong Xu, Yougang Wang, Wenxiu Yang, Ran Li & Xuelei Chen

  3. Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, Beijing, China

    Yidong Xu, Yougang Wang & Xuelei Chen

  4. School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing, China

    Wenxiu Yang, Ran Li & Xuelei Chen

  5. Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing, China

    Ran Li

  6. National Frontiers Science Center for Industrial Intelligence and Systems Optimization, Northeastern University, Shenyang, China

    Xin Zhang

  7. Key Laboratory of Data Analytics and Optimization for Smart Industry (Ministry of Education), Northeastern University, Shenyang, China

    Xin Zhang

  8. Center for High Energy Physics, Peking University, Beijing, China

    Xuelei Chen

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Contributions

Y.S. performed most of the computation and analysis, and wrote part of the paper. Y.X. led the study, contributed to the simulations and wrote the majority of the paper. Y.W. and W.Y. contributed to the computation of the 1D power spectrum. Y.X. and R.L. proposed the study. X.Z. and X.C. contributed to the collaboration organization, the Fisher forecasts and the writing of the paper, and supervised the study. All authors discussed the results and commented on the paper.

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Correspondence to Yidong Xu, Xin Zhang or Xuelei Chen.

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Extended data

Extended Data Fig. 1 The overdensity (left panel), optical depth (middle panel) and brightness temperature (right panel) for a line of sight of 2 comoving Mpc in the CDM model at z = 9.

The green, yellow and red lines correspond to local overdensities of δ0 = 0, 1 and 2, respectively. The flux density of the background source in the right panel is assumed to be S150 = 10 mJy.

Source data

Extended Data Fig. 2 1-D power spectrum of a synthetic 21-cm forest spectrum in the CDM model, for a line of sight penetrating through an unheated IGM (fX = 0) with different local overdensities at z = 9.

The green, yellow and red curves correspond to δ0 = 0, 1 and 2, respectively. The flux density of the background source is assumed to be S150 = 10 mJy.

Source data

Supplementary information

Supplementary Information

Supplementary Figs. 1–9.

Source data

Source Data Fig. 1

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Source Data Fig. 2

Statistical source data.

Source Data Fig. 3

Statistical source data.

Source Data Fig. 4

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Source Data Fig. 5

Statistical source data.

Source Data Fig. 6

Statistical source data.

Source Data Extended Data Fig. 1

Statistical source data.

Source Data Extended Data Fig. 2

Statistical source data.

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Shao, Y., Xu, Y., Wang, Y. et al. The 21-cm forest as a simultaneous probe of dark matter and cosmic heating history. Nat Astron 7, 1116–1126 (2023). https://doi.org/10.1038/s41550-023-02024-7

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