The impact of non-Gaussianity on the error covariance for observations of the Epoch of Reionization (EoR) 21-cm power spectrum. (arXiv:1902.08706v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Shaw_A/0/1/0/all/0/1">Abinash Kumar Shaw</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bharadwaj_S/0/1/0/all/0/1">Somnath Bharadwaj</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mondal_R/0/1/0/all/0/1">Rajesh Mondal</a>
Recent simulations have shown the EoR 21-cm signal to be inherently
non-Gaussian whereby the error covariance matrix $mathbf{{C}}_{ij}$ of the
21-cm power spectrum (PS) contains a trispectrum contribution which would be
absent if the signal were Gaussian. Using the binned power spectrum and
trispectrum from simulations, in this paper we present a methodology for
incorporating these with the baseline distribution and system noise to make
error predictions for observations with any radio-interferometric array. Here
we consider the upcoming SKA-Low, assuming no foreground contamination.
Non-Gaussianity enhances the errors introducing a positive deviation $Delta$
relative to the Gaussian predictions. $Delta$ increases with observation time
$t_{rm obs}$ and saturates as the errors approach the cosmic variance.
Considering $t_{rm obs}=1,024$ hrs where a $5 sigma$ detection is possible at
all redshifts $7 le z le 13$, we find that the deviations are important at
small $k$ where we have $Delta sim 40-100 %$ at $k sim 0.04 ~{rm
Mpc}^{-1}$ for some of the redshifts and also at intermediate $k , (sim 0.4
~{rm Mpc}^{-1})$ where we have $Delta sim 200 %$ at $z=7$. Non-Gaussianity
also introduces correlations between the errors in different $k$ bins, and we
find both correlations and anti-correlations with the correlation coefficient
value spanning $-0.4 le r_{ij} le 0.8$. We conclude that non-Gaussianity
makes a significant contribution to the errors and this is important in the
context of the future instruments which aim to achieve high sensitivity
measurements of the EoR 21-cm PS.
Recent simulations have shown the EoR 21-cm signal to be inherently
non-Gaussian whereby the error covariance matrix $mathbf{{C}}_{ij}$ of the
21-cm power spectrum (PS) contains a trispectrum contribution which would be
absent if the signal were Gaussian. Using the binned power spectrum and
trispectrum from simulations, in this paper we present a methodology for
incorporating these with the baseline distribution and system noise to make
error predictions for observations with any radio-interferometric array. Here
we consider the upcoming SKA-Low, assuming no foreground contamination.
Non-Gaussianity enhances the errors introducing a positive deviation $Delta$
relative to the Gaussian predictions. $Delta$ increases with observation time
$t_{rm obs}$ and saturates as the errors approach the cosmic variance.
Considering $t_{rm obs}=1,024$ hrs where a $5 sigma$ detection is possible at
all redshifts $7 le z le 13$, we find that the deviations are important at
small $k$ where we have $Delta sim 40-100 %$ at $k sim 0.04 ~{rm
Mpc}^{-1}$ for some of the redshifts and also at intermediate $k , (sim 0.4
~{rm Mpc}^{-1})$ where we have $Delta sim 200 %$ at $z=7$. Non-Gaussianity
also introduces correlations between the errors in different $k$ bins, and we
find both correlations and anti-correlations with the correlation coefficient
value spanning $-0.4 le r_{ij} le 0.8$. We conclude that non-Gaussianity
makes a significant contribution to the errors and this is important in the
context of the future instruments which aim to achieve high sensitivity
measurements of the EoR 21-cm PS.
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