tokens: this work we do not see a wedge structure due to the incomplete treatment of instrumental frequency dependence. This will be addressed in future work. We have however included two theoretical lines relating to the wedge limit on all figures – a dashed line which assumes sources in the entire field of view (in our case 10 deg) will leak into the main field and an optimistic solid line which assumes only sources within the chosen central 4 deg (approximately the full width at half-maximum – FWHM – of the station beam) will affect the image. Further work on the contamination within the wedge is ongoing in the literature and as such recovery below the theoretical wedge line should be treated with caution. We refer to the combination of the noise, dirty foregrounds and dirty cosmological signal as the ‘total input signal’. We refer to the foreground model estimated by GMCA as the ‘reconstructed foregrounds’ and the difference between the reconstructed foregrounds and the total input signal as the ‘residuals’, which will contain the cosmological signal, noise and any foreground fitting errors. The foreground fitting errors can be defined as the difference between the simulated foregrounds and the reconstructed foregrounds and will contain any cosmological signal or noise which has been fitted as foregrounds as well as an absence of any foregrounds not modelled. 5 RESULTS Unless otherwise stated we present results for cylindrical power spectrum calculated over a 10 MHz bandwidth segment centred at 165 MHz, where the variance of the cosmological signal peaks in our simulation. This bandwidth is formed using an extended Blackmann–Nuttall window, though other windows are possible, as discussed in Section 5.1 . We 3D Fourier transform the data segment and bin the data according to the values of k perp , k los . The power at any particular k los , k perp , P ( k los , k perp ) = 〈δ( k los , k perp )δ*( k los , k perp )〉 is the average power of all the uv cells in the bin centring on k los , k perp . We choose to plot the ‘dimensionless’ power spectrum, , which has units of mK 2 throughout this paper: where V is the volume of the 10 MHz bandwidth in Mpc. We first construct cylindrical power spectrum for the different signal contributions in order to understand how the EoR window is constructed. In Fig. 1 , we see the Galactic synchrotron, Galactic free–free and unresolved extragalactic foregrounds while in Fig. 2 we see the dirty cosmological signal and dirty foregrounds (with all three foreground contributions summed). The action of the PSF can be clearly seen as a loss of power on scales above this (i.e. for k perp > 0.65 Mpc −1 ). Note that, since we are seeing power spectrum over a 10 MHz bandwidth only we do not see the evolution of the cosmological signal over redshift. We see clearly the area of k -space where the foregrounds appear to be at their strongest is at low k los , however, it should be noted that there is appreciable foreground
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