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Exploring the Epoch of Reionisation with Wavelets

The statistical study of the Epoch of Reionisation (EoR) involves computing the power spectrum (variance) of the signal as a function of spatial wavenumber (k, measured in inverse Mpc). The angular scales are obtained by Fourier Transform of radio astronomy images, or equivalently, direct use of the visibilities measured by an interferometer. The line-of-sight scales are computed by obtaining data in individual frequency channels, mapping those channels to cosmological distances, and taking the Fourier Transform across frequency. This procedure assumes that the information within the observation volume (FOV × depth) is statistically equivalent. However, the 21cm cosmological signal of the EoR evolves with redshift, and taking Fourier Transforms over large redshift ranges dilutes and biases the signal. In Trott (2016, MNRAS 1310), we proposed using wavelets to perform wide bandwidth analysis, but with localised properties. This project takes those initial explorations and applies the methods to existing MWA data. We aim to study the impact of foreground contamination in the wavelet space, and refine our wavelet methods based on optimising signal relative to noise and contamination.