The wedge bias in reionization 21-cm power spectrum measurements

Abstract

A proposed method for dealing with foreground emission in upcoming 21-cm observations from the epoch of reionization is to limit observations to an uncontaminated window in Fourier space. Foreground emission can be avoided in this way, since it is limited to a wedge-shaped region in $k_{\parallel },k_{\perp }$ space. However, the power spectrum is anisotropic owing to redshift-space distortions from peculiar velocities. Consequently, the 21-cm power spectrum measured in the foreground avoidance window---which samples only a limited range of angles close to the line-of-sight direction---differs from the full spherically-averaged power spectrum which requires an average over \emph{all} angles. In this paper, we calculate the magnitude of this "wedge bias" for the first time. We find that the bias is strongest at high redshifts, where measurements using foreground avoidance will over-estimate the power spectrum by around 100 per cent, possibly obscuring the distinctive rise and fall signature that is anticipated for the spherically-averaged 21-cm power spectrum. In the later stages of reionization, the bias becomes negative, and smaller in magnitude ($\lesssim 20$ per cent). The effect shows only a weak dependence on spatial scale and reionization topology.

Accepted for publication in MNRAS

References in corpus (10)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• The Epoch of Reionization Window: I. Mathematical Formalism
• Inside-out or Outside-in: The topology of reionization in the photon-starved regime suggested by Lyman-alpha forest data
• The Scale of the Problem : Recovering Images of Reionization with GMCA
• 21 cm signal from cosmic dawn: Imprints of spin temperature fluctuations and peculiar velocities
• Power spectrum extraction for redshifted 21-cm epoch of reionization experiments: the LOFAR case
• On the use of semi-numerical simulations in predicting the 21-cm signal from the epoch of reionization
• Light cone effect on the reionization 21-cm signal II: Evolution, anisotropies and observational implications
• The Impact of Foregrounds on Redshift Space Distortion Measurements With the Highly-Redshifted 21 cm Line
• 21-cm signal from cosmic dawn - II: Imprints of the light-cone effects

Cited by in corpus (26)

• Data Analysis for Precision 21 cm Cosmology
• HERA Phase I Limits on the Cosmic 21-cm Signal: Constraints on Astrophysics and Cosmology During the Epoch of Reionization
• Statistical 21-cm Signal Separation via Gaussian Process Regression Analysis
• Bubble size statistics during reionization from 21-cm tomography
• Inflation and Early Dark Energy with a Stage II Hydrogen Intensity Mapping Experiment
• Spherical Harmonic Analyses of Intensity Mapping Power Spectra
• Position-dependent power spectra of the 21-cm signal from the epoch of reionization
• The visibility based Tapered Gridded Estimator (TGE) for the redshifted 21-cm power spectrum
• Probing the Intergalactic Medium with Ly$\alpha$ and 21 cm Fluctuations
• Redshift-space distortions in simulations of the 21-cm signal from the cosmic dawn
• Foreground modelling via Gaussian process regression: an application to HERA data
• The effect of baseline layouts on the EoR foreground wedge: a semi-analytical approach
• An Effective Bias Expansion for 21 cm Cosmology in Redshift Space
• An Improved Statistical Point-Source Foreground Model for the Epoch of Reionization
• A Model-Insensitive Baryon Acoustic Oscillation Feature in the 21 cm Signal from Reionization
• Variations in fundamental constants at the cosmic dawn
• Emulation of the Cosmic Dawn 21-cm Power Spectrum and Classification of Excess Radio Models Using an Artificial Neural Network
• Generating extremely large-volume reionisation simulations
• Mapping discrete galaxies at cosmic dawn with 21-centimeter observations
• Unlocking Sensitivity for Visibility-based Estimators of the 21 cm Reionization Power Spectrum
• Line of sight anisotropies in the Cosmic Dawn and EoR 21-cm power spectrum
• Measuring the reionization 21 cm fluctuations using clustering wedges
• Measurements of one-point statistics in 21 cm intensity maps via foreground avoidance strategy
• Understanding spectral artefacts in SKA-LOW 21-cm cosmology experiments: the impact of cable reflections
• Classification of Radio Backgrounds at Cosmic Dawn and 21 cm Signal Confirmation Using Neural Networks
• Power spectrum multipoles and clustering wedges during the Epoch of Reionization