Large-Scale Non-Gaussianities in the 21 cm Background Anisotropies From the Era of Reionization

Abstract

The brightness temperature fluctuations in the 21 cm background related to neutral Hydrogen distribution provide a probe of physics related to the era of reionization when the intergalactic medium changed from a completely neutral to a partially ionized one. We formulate statistics of 21 cm brightness temperature anisotropies in terms of the angular power spectrum, the bispectrum, and the trispectrum. Using the trispectrum, we estimate the covariance related to the power spectrum measurements and show that correlations resulting from non-Gaussianities are below a percent, at most. While all-sky observations of the 21 cm background at arcminute-scale resolution can be used to measure the bispectrum with a cumulative signal-to-noise ratio of order a few ten, in the presence of foregrounds and instrumental noise related to first-generation interferometers, the measurement is unlikely to be feasible. For most purposes, non-Gaussianities in 21 cm fluctuations can be ignored and the distribution can be described with Gaussian statistics. Since 21 cm fluctuations are significantly contaminated by foregrounds, such as galactic synchrotron or low-frequency radio point sources, the lack of a significant non-Gaussianity in the signal suggests that any significant detection of a non-Gaussianity can be due to foregrounds. Similarly, in addition to frequency information that is now proposed to separate 21 cm fluctuations from foregrounds, if the non-Gaussian structure of foregrounds is a priori known, one can potentially use this additional information to further reduce the confusion.

8 pages, 3 figures

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Cited by in corpus (28)

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• 21-cm Background Anisotropies Can Discern Primordial Non-Gaussianity
• The bispectrum of redshifted 21-cm fluctuations from the dark ages
• 21cm-line bispectrum as method to probe Cosmic Dawn and Epoch of Reionization
• Primordial non-Gaussianity in the large scale structure of the Universe
• The trispectrum of 21-cm background anisotropies as a probe of primordial non-Gaussianity
• Probing Primordial Magnetic Fields with the 21cm Fluctuations
• Sensitivity for 21cm Bispectrum from Epoch of Reionization
• Recovering the HII region size statistics from 21-cm tomography
• The Hunt for Primordial Interactions in the Large Scale Structures of the Universe
• Studying 21cm power spectrum with one-point statistics
• Redshift space 21 cm power spectra from reionization
• Prospects of constraining reionization model parameters using Minkowski tensors and Betti numbers
• Studying the morphology of HI isodensity surfaces during reionization using Shapefinders and percolation analysis
• The effects of primordial non-Gaussianity on the cosmological reionization
• Primordial trispectra and CMB spectral distortions
• Violation of statistical isotropy and homogeneity in the 21-cm power spectrum
• Angular dependence of primordial trispectra and CMB spectral distortions
• CMB constraints on running non-Gaussianity
• Exploring the cosmic dawn and epoch of reionization with 21cm line
• Generating extremely large-volume reionisation simulations
• Probing a panoply of curvaton-decay scenarios using CMB data
• Non-Gaussianity of diffuse Galactic synchrotron emission at 408 MHz
• Testing the scale-dependent hemispherical asymmetry with the 21-cm power spectrum from the epoch of reionization
• Studying neutral hydrogen structures during the epoch of reionization using fractal dimensions
• The Impact of ionization Morphology and X-ray Heating on the Cosmological 21cm Skew Spectrum
• Probing Cosmological Reionization through Radio-interferometric Observations of Neutral Hydrogen