Mondal, Rajesh ; Bharadwaj, Somnath ; Majumdar, Suman (2016) Statistics of the epoch of reionization (EoR) 21-cm signal – II. The evolution of the power-spectrum error-covariance Monthly Notices of the Royal Astronomical Society, 464 (3). pp. 2992-3004. ISSN 0035-8711
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Official URL: http://doi.org/10.1093/mnras/stw2599
Related URL: http://dx.doi.org/10.1093/mnras/stw2599
Abstract
The epoch of reionization (EoR) 21-cm signal is expected to become highly non-Gaussian as reionization progresses. This severely affects the error-covariance of the EoR 21-cm power spectrum that is important for predicting the prospects of a detection with ongoing and future experiments. Most earlier works have assumed that the EoR 21-cm signal is a Gaussian random field where (1) the error-variance depends only on the power spectrum and the number of Fourier modes in the particular k bin, and (2) the errors in the different k bins are uncorrelated. Here, we use an ensemble of simulated 21-cm maps to analyse the error-covariance at various stages of reionization. We find that even at the very early stages of reionization (| $\bar{x}_{\rm H\,{\small \small {I}}}\sim 0.9$ |), the error-variance significantly exceeds the Gaussian predictions at small length-scales (k > 0.5 Mpc−1) while they are consistent at larger scales. The errors in most k bins (both large and small scales) are however found to be correlated. Considering the later stages (| $\bar{x}_{\rm H\,{\small \small {I}}}=0.15$ |), the error-variance shows an excess in all k bins within k ≥ 0.1 Mpc−1, and it is around 200 times larger than the Gaussian prediction at k ∼ 1 Mpc−1. The errors in the different k bins are all also highly correlated, barring the two smallest k bins that are anti-correlated with the other bins. Our results imply that the predictions for different 21-cm experiments based on the Gaussian assumption underestimate the errors, and it is necessary to incorporate the non-Gaussianity for more realistic predictions.
Item Type: | Article |
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Source: | Copyright of this article belongs to The Royal Astronomical Society. |
Keywords: | Methods: Statistical; Cosmology: Theory; Dark Ages; Reionization; First Stars; Diffuse Radiation; Large-scale Structure Of Universe. |
ID Code: | 116312 |
Deposited On: | 09 Apr 2021 04:29 |
Last Modified: | 09 Apr 2021 04:29 |
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