Papers › Detecting the HI Power Spectrum in the Post-Reionization Universe with SKA-Low

Detecting the HI Power Spectrum in the Post-Reionization Universe with SKA-Low

22 Feb 2023arXiv:2302.11504links table onlyarchive 2025-07-28

Zhaoting Chen, Emma Chapman, Laura Wolz, Aishrila Mazumder

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We present a survey strategy to detect the neutral hydrogen (HI) power spectrum at 5<z<6 using the SKA-Low radio telescope in presence of foregrounds and instrumental effects. We simulate observations of the inherently weak HI signal post-reionization with varying levels of noise and contamination with foreground amplitudes equivalent to residuals after sky model subtraction. We find that blind signal separation methods on imaged data are required in order to recover the HI signal at large cosmological scales. Comparing different methods of foreground cleaning, we find that Gaussian Process Regression (GPR) performs better than Principle Component Analysis (PCA), with the key difference being that GPR uses smooth kernels for the total data covariance. The integration time of one field needs to be larger than ∼250 h to provide large enough signal-to-noise ratio (SNR) to accurately model the data covariance for foreground cleaning. Images within the primary beam field-of-view give measurements of the HI power spectrum at scales k∼0.02 Mpc⁻¹-0.3 Mpc⁻¹ with SNR ∼2-5 in Δ[log( k/Mpc⁻¹)] = 0.25 bins assuming an integration time of 600 h. Systematic effects, which introduce small-scale fluctuations across frequency channels, need to be ≲5×10⁻⁵ to enable unbiased measurements outside the foreground wedge. Our results provide an important validation towards using the SKA-Low array for measuring the HI power spectrum in the post-reionization Universe.

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