Anatomy of Cosmic Tidal Reconstruction

Abstract

21-cm intensity surveys aim to map neutral hydrogen atoms in the universe through hyper-fine emission. Unfortunately, long-wavelength (low-wavenumber) radial modes are highly contaminated by smooth astrophysical foregrounds that are six orders of magnitude brighter than the cosmological signal. This contamination also leaks into higher radial and angular wavenumber modes and forms a foreground wedge. Cosmic tidal reconstruction aims to extract the large-scale signal from anisotropic features in the local small-scale power spectrum through non-linear tidal interactions; losing small-scale modes to foreground wedge will impair its performance. In this paper, we review tidal interaction theory and estimator construction, and derive the theoretical expressions for the reconstructed spectra. We show the reconstruction is robust against peculiar velocities. Removing low line-of-sight $k$ modes, we demonstrate cross-correlation coefficient $r$ is greater than 0.7 on large scales ($k<0.1$ $h/$Mpc) even with a cutoff value $k_{\Vert }^c=0.1$ $h/$Mpc. Discarding wedge modes yields $0.3<r<0.5$ and completely removes the dependency on $k_{\Vert }^c$. Our theoretical predictions agree with these numerical simulations.

arXiv comment10 pages, 6 figures

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• Data Analysis for Precision 21 cm Cosmology
• Reconstructing large-scale structure with neutral hydrogen surveys
• Inflation and Early Dark Energy with a Stage II Hydrogen Intensity Mapping Experiment
• Forecasts on Primordial non-Gaussianity from 21 cm Intensity Mapping experiments
• Recovering the Wedge Modes Lost to 21-cm Foregrounds
• Cosmological constraints from the power spectrum and bispectrum of 21cm intensity maps
• Probing primordial non-Gaussianity with the power spectrum and bispectrum of future 21cm intensity maps
• Density reconstruction from biased tracers and its application to primordial non-Gaussianity
• Cosmic Tidal Reconstruction with Halo Fields
• Reconstructing the Long-wavelength Matter Density Fluctuation Modes from the Scalar-Type Clustering Fossils
• Mind the gap: the power of combining photometric surveys with intensity mapping
• Direct correlation of line intensity mapping and CMB lensing from evolution along the lightcone
• Squeezing information from radio surveys to probe the primordial Universe