Suppressing variance in 21-cm signal simulations during reionization

Abstract

Current best limits on the 21-cm signal during reionization are provided at large scales ($\gtrsim$100 Mpc). To model these scales, enormous simulation volumes are required which are computationally expensive. We find that the primary source of uncertainty at these large scales is sample variance, which decides the minimum size of simulations required to analyse current and upcoming observations. In large-scale structure simulations, the method of `fixing' the initial conditions (ICs) to exactly follow the initial power spectrum and `pairing' two simulations with exactly out-of-phase ICs has been shown to significantly reduce sample variance. Here we apply this `fixing and pairing' (F\&P) approach to reionization simulations whose clustering signal originates from both density fluctuations and reionization bubbles. Using a semi-numerical code, we show that with the traditional method, simulation boxes of $L\simeq 500$ (300) Mpc are required to model the large-scale clustering signal at $k$=0.1 Mpc${}^{-1}$ with a precision of 5 (10) per cent. Using F\&P, the simulation boxes can be reduced by a factor of 2 to obtain the same precision level. We conclude that the computing costs can be reduced by at least a factor of 4 when using the F\&P approach.

5 pages, 4 figures, accepted for publication in A&A

References in corpus (14)

• Efficient Simulations of Early Structure Formation and Reionization
• Improved upper limits on the 21-cm signal power spectrum of neutral hydrogen at $\mathbf{z}\approx 9.1$ from LOFAR
• 21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal
• Introducing the THESAN project: radiation-magnetohydrodynamic simulations of the epoch of reionization
• Deep multi-redshift limits on Epoch of Reionisation 21cm Power Spectra from Four Seasons of Murchison Widefield Array Observations
• First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum
• Euclid preparation: IX. EuclidEmulator2 -- Power spectrum emulation with massive neutrinos and self-consistent dark energy perturbations
• Constraining the intergalactic medium at $z\approx$ 9.1 using LOFAR Epoch of Reionization observations
• Constraining the state of the intergalactic medium during the Epoch of Reionization using MWA 21-cm signal observations
• A halo model approach for the 21-cm power spectrum at cosmic dawn
• Redshift-space distortions in simulations of the 21-cm signal from the cosmic dawn
• The large-scale 21-cm power spectrum from reionization
• Statistics of biased tracers in variance-suppressed simulations
• Generating extremely large-volume reionisation simulations

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• pyC${}^2$Ray: A flexible and GPU-accelerated Radiative Transfer Framework for Simulating the Cosmic Epoch of Reionization
• Efficient exploration of reionization parameters for the upcoming 21 cm observations using a photon conserving semi-numerical model SCRIPT
• Mapping neutral islands during end stages of reionization with photometric intergalactic medium tomography
• Impact of anisotropic photon emission from sources during the epoch of reionisation
• Sample Variance Denoising in Cylindrical 21-cm Power Spectra