Impact of Stochastic Pop III X-ray Binaries on the Cosmological 21-cm Signal
6 affiliations
- 1Institute of Astronomy, University of Cambridge , Madingley Road, Cambridge, CB3 0HA ,
- 2Kavli Institute for Cosmology , Madingley Road, Cambridge, CB3 0HA ,
- 3Institut für Theoretische Astrophysik, Zentrum für Astronomie , Universität Heidelberg, Albert Ueberle Straße 2, D-69120 Heidelberg ,
- 4National Astronomical Observatories, Chinese Academy of Sciences , 20A Datun Road, Chaoyang District, Beijing 100101 ,
- 5School of Astronomy and Space Science, University of Chinese Academy of Sciences , No.1 Yanqihu East Rd, Huairou District, Beijing 101408 ,
- 6School of Physics and Astronomy, Tel Aviv University , Tel Aviv 69978 ,
Abstract
High-mass X-ray binaries are one of the primary drivers of the 21-cm signal from Cosmic Dawn and Reionization, playing a leading role in the thermal history of the intergalactic medium. In traditional semi-numerical simulations, a deterministic scaling relation between the total X-ray luminosity of high-mass X-ray binaries, LX, and star formation rate (SFR) is usually adopted. However, this assumption is inaccurate for high-redshift low-SFR regions hosting few sources. The spatial variation in the number and luminosity of these sources is expected to enhance fluctuations in the Cosmic Dawn 21-cm signal. Here we quantify this effect by introducing a stochastic LX model sampled from a power-law X-ray luminosity function. Implementing this in 21cmSPACE, a large-scale simulation framework of Cosmic Dawn and Reionization, and adopting a soft X-ray spectral energy distribution (β = 1.5, Emin = 0.1 keV) that leads to a relatively strong stochastic signature, we find that the stochasticity leads to enhanced fluctuations in X-ray heating rate fields, and affects the 21-cm power spectrum on small scales (k > 0.3 cMpc−1). The impact of stochasticity on the global 21-cm signal and on the large-scale power spectrum is found to be negligible. Our results suggest these effects will remain undetected by the upcoming Square Kilometer Array. However, large-scale lunar-based experiments may be sensitive to the signatures of stochastic X-ray heating at z ∼ 25. Quantifying these corrections is a vital step toward robust 21-cm modeling and ensuring that future precision data interpretation is free from astrophysical biases.
Related
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BibTeX
@article{dasgupta2026impact,
title = {{Impact of Stochastic Pop III X-ray Binaries on the Cosmological 21-cm Signal}},
author = {Saswata Dasgupta and Boyuan Liu and Anastasia Fialkov and Furen Deng and Jiten Dhandha and Rennan Barkana},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = oct,
doi = {10.1093/mnras/stag1997},
url = {https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1997/8965443},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Impact of Stochastic Pop III X-ray Binaries on the Cosmological 21-cm Signal
AU - Saswata Dasgupta
AU - Boyuan Liu
AU - Anastasia Fialkov
AU - Furen Deng
AU - Jiten Dhandha
AU - Rennan Barkana
PY - 2026
DA - 2026/10/21
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1997
UR - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag1997/8965443
AB - High-mass X-ray binaries are one of the primary drivers of the 21-cm signal from Cosmic Dawn and Reionization, playing a leading role in the thermal history of the intergalactic medium. In traditional semi-numerical simulations, a deterministic scaling relation between the total X-ray luminosity of high-mass X-ray binaries, LX, and star formation rate (SFR) is usually adopted. However, this assumption is inaccurate for high-redshift low-SFR regions hosting few sources. The spatial variation in the number and luminosity of these sources is expected to enhance fluctuations in the Cosmic Dawn 21-cm signal. Here we quantify this effect by introducing a stochastic LX model sampled from a power-law X-ray luminosity function. Implementing this in 21cmSPACE, a large-scale simulation framework of Cosmic Dawn and Reionization, and adopting a soft X-ray spectral energy distribution (β = 1.5, Emin = 0.1 keV) that leads to a relatively strong stochastic signature, we find that the stochasticity leads to enhanced fluctuations in X-ray heating rate fields, and affects the 21-cm power spectrum on small scales (k > 0.3 cMpc−1). The impact of stochasticity on the global 21-cm signal and on the large-scale power spectrum is found to be negligible. Our results suggest these effects will remain undetected by the upcoming Square Kilometer Array. However, large-scale lunar-based experiments may be sensitive to the signatures of stochastic X-ray heating at z ∼ 25. Quantifying these corrections is a vital step toward robust 21-cm modeling and ensuring that future precision data interpretation is free from astrophysical biases.
SN - 0035-8711
SN - 1365-2966
ER -