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Simulation based inference of the ionization history from the 2D 21 cm power spectrum

N Cooper, C Norregaard, R Meriot… - arXiv preprint arXiv …, 2025 - arxiv.org
Astrophysics paper astro-ph.CO Suggest

… In this work we have contrasted two simulation based inference methods for inference from the 21 cm signal. We inferred astrophysical parameters of our model, …

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BibTeX

@article{2508.16329v1,
Author        = {Nadia Cooper and Carina Norregaard and Romain Meriot and Jonathan R. Pritchard},
Title         = {Simulation based inference of the ionization history from the 2D 21 cm
  power spectrum},
Eprint        = {2508.16329v1},
ArchivePrefix = {arXiv},
PrimaryClass  = {astro-ph.CO},
Abstract      = {The 21 cm signal contains a wealth of information about the formation of the
first stars and the reionization of the intergalactic medium during the Cosmic
Dawn (CD) and Epoch of Reionization (EoR). The timing of these important
milestones has only roughly been constrained through indirect measurements,
such as from the cosmic microwave background (CMB) optical depth, and
Lyman-$\alpha$ forest. Therefore, inferring the neutral fraction over cosmic
time is a goal of upcoming 21 cm experiments, such as the Square Kilometer
Array (SKA). We contrast two approaches to infer astrophysical parameters and
ionization history from 21 cm 2D power spectra (2DPS). We develop an emulator
of the 21 cm 2DPS, trained on 21cmFAST simulations, taking into account the
expected instrumental noise from the SKA and sample variance. We then perform
simulation based inference (SBI) using neural posterior estimation (NPE). We
compare training on datasets of noisy 2DPS obtained from 21cmFAST simulations
and an emulator, to infer astrophysical parameters of interest. Using an
emulator of the ionization history, which has been trained on simulations from
the same astrophysical parameters, we then obtain posterior distributions of
the ionization history over the redshift range z $\sim$ 5-12. We demonstrate
that both methods are capable of accurately recovering the ionization history
and astrophysical parameters. However, coverage tests indicate that adding
emulated samples does not improve predictions. This work suggests that due to
the stochastic nature of the 2DPS, using an emulator of this summary statistic
may result in poorer inference.},
Year          = {2025},
Month         = {Aug},
Url           = {http://arxiv.org/abs/2508.16329v1},
File          = {2508.16329v1.pdf}
}

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