Exploring the likelihood of the 21-cm power spectrum with simulation-based inference

Abstract

Observations of the cosmic 21-cm power spectrum (PS) are starting to enable precision Bayesian inference of galaxy properties and physical cosmology, during the first billion years of our Universe. Here we investigate the impact of common approximations about the likelihood used in such inferences, including: (i) assuming a Gaussian functional form; (ii) estimating the mean from a single realization; and (iii) estimating the (co)variance at a single point in parameter space. We compare "classical" inference that uses an explicit likelihood with simulation based inference (SBI) that estimates the likelihood from a training set. Our forward-models include: (i) realizations of the cosmic 21-cm signal computed with 21cmFAST by varying UV and X-ray galaxy parameters together with the initial conditions; (ii) realizations of the telescope noise corresponding to a 1000 h integration with SKA1-Low; (iii) the excision of Fourier modes corresponding to a foreground-dominated, horizon "wedge". We find that the 1D PS likelihood is well described by a Gaussian accounting for covariances between wavemodes and redshift bins (higher order correlations are small). However, common approaches of estimating the forward-modeled mean and (co)variance from a random realization or at a single point in parameter space result in biased and over-constrained posteriors. Our best results come from using SBI to fit a non-Gaussian likelihood with a Gaussian mixture neural density estimator. Such SBI can be performed with up to an order of magnitude fewer simulations than classical, explicit likelihood inference. Thus SBI provides accurate posteriors at a comparably low computational cost.

16 pages, 12 figures, updated to match the version accepted for publication in MNRAS

References in corpus (21)

• UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
• Model-independent evidence in favor of an end to reionization by z~6
• 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
• The Epoch of Reionization Window: I. Mathematical Formalism
• 21 cm fluctuations from inhomogeneous X-ray heating before reionization
• 21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal
• A statistical test for Nested Sampling algorithms
• Deep multi-redshift limits on Epoch of Reionisation 21cm Power Spectra from Four Seasons of Murchison Widefield Array Observations
• Fast likelihood-free cosmology with neural density estimators and active learning
• The Epoch of Reionization Window: II. Statistical Methods for Foreground Wedge Reduction
• 21cmFAST v3: A Python-integrated C code forgenerating 3D realizations of the cosmic 21cm signal
• Bayesian reconstruction of the cosmological large-scale structure: methodology, inverse algorithms and numerical optimization
• Constraining the intergalactic medium at $z\approx$ 9.1 using LOFAR Epoch of Reionization observations
• Emulation of reionization simulations for Bayesian inference of astrophysics parameters using neural networks
• SIBELIUS-DARK: a galaxy catalogue of the Local Volume from a constrained realisation simulation
• Exploring the cosmic 21-cm signal from the Epoch of Reionisation using the Wavelet Scattering Transform
• The impact of non-Gaussianity on the error covariance for observations of the Epoch of Reionization 21-cm power spectrum
• Inferring the properties of the sources of reionization using the morphological spectra of the ionized regions
• The multi-frequency angular power spectrum in parameter studies of the cosmic 21-cm signal
• Inferring reionization and galaxy properties from the patchy kinetic Sunyaev-Zel'dovich signal

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• Efficient simulation of discrete galaxy populations and associated radiation fields during the first billion years
• Detecting galaxy-21-cm cross-correlation during reionization
• Analyzing the 21cm forest with Wavelet Scattering Transform: Insight into non-Gaussian features of the 21cm forest
• Comparing sampling techniques to chart parameter space of 21 cm Global signal with Artificial Neural Networks
• Simulation-based inference has its own Dodelson-Schneider effect (but it knows that it does)
• Comparison of Bayesian inference methods using the Loreli II database of hydro-radiative simulations of the 21-cm signal
• Fisher matrix forecasts on the astrophysics of galaxies during the epoch of reionisation from the 21-cm power spectra
• The 21cm-galaxy cross-correlation: Realistic forecast for 21cm signal detection and reionisation constraints
• Narrowing the discovery space of the cosmological 21-cm signal using multi-wavelength constraints
• Reionization Parameter Inference from 3D Minkowski Functionals of the 21 cm Signals
• From ANN to BNN: Inferring Reionization Parameters using Uncertainty-aware Emulators of 21-cm Summaries
• Quantifying Weighted Morphological Content of Large-Scale Structures via Simulation-Based Inference
• Sample Variance Denoising in Cylindrical 21-cm Power Spectra
• Large Language Models -- the Future of Fundamental Physics?
• Simulation based inference of the ionization history from the 2D 21 cm power spectrum
• Exploring the Early Universe with Deep Learning
• Beyond the Power Spectrum: A New Framework for Non-Stationary Fields with Applications to Light-Cone Effects in Line Intensity Mapping