The impact of non-Gaussianity on the error covariance for observations of the Epoch of Reionization 21-cm power spectrum

被引:27
作者
Shaw, Abinash Kumar [1 ,2 ]
Bharadwaj, Somnath [1 ,2 ]
Mondal, Rajesh [3 ]
机构
[1] Indian Inst Technol Kharagpur, Dept Phys, Kharagpur 721302, W Bengal, India
[2] Indian Inst Technol Kharagpur, Ctr Theoret Studies, Kharagpur 721302, W Bengal, India
[3] Univ Sussex, Dept Phys & Astron, Astron Ctr, Brighton BN1 9QH, E Sussex, England
基金
英国科学技术设施理事会;
关键词
large-scale structure of universe; first stars; cosmology: reionization; diffuse radiation; methods: statistical; technique: interferometric; 21 CM RADIATION; REDSHIFTED; 21-CM; NEUTRAL HYDROGEN; FOREGROUND SUBTRACTION; HI FLUCTUATIONS; NEXT-GENERATION; 150; MHZ; EVOLUTION; SIGNAL; Z-SIMILAR-TO-6;
D O I
10.1093/mnras/stz1561
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Recent simulations show the Epoch of Reionization (EoR) 21-cm signalto be inherently non-Gaussian whereby the error covariance matrix of the 21-cm power spectrum (PS) contains a trispectrum contribution that would be absent if the signal were Gaussian. Using the binned power spectrum and trispectrum from simulations, here 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. Non-Gaussianity enhances the errors introducing a positive deviation Delta relative to the Gaussian predictions. Delta increases with observation time t(obs) and saturates as the errors approach the cosmic variance. Considering t(obs)= 1024 hours where a 5 sigma detection is possible at all redshifts 7 <= z <= 13, in the absence of foregrounds we find that the deviations are important at small k where we have at for some of the redshifts and also at intermediate where we have at z= 7. Non-Gaussianity also introduces correlations between the errors in different k bins, and we find both correlations and anticorrelations with the correlation coefficient value spanning -0.4 <= r(ij)<= 0.8. Incorporating the foreground wedge, Delta continues to be important () at z= 7. We conclude that non-Gaussianity makes a significant contribution to the errors and this is important in the context of the future instruments that aim to achieve high-sensitivity measurements of the EoR 21-cm PS.
引用
收藏
页码:4951 / 4964
页数:14
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