resolution. We, therefore, make images at coarser $2^{'}$ resolution in order to keep the noise contribution under control. In order to achieve the default images with $2^{'}$ resolution, we consider baselines only up to $U\sim1720$ and discard larger baselines. We note that only a negligible fraction of the total baselines would be discarded in this process as most of the antennae for the SKA1-low are packed at the central region (see right-hand panel of Figure \[image\_ska\_base\_alter\]). Depending on the values of $\theta_{\rm max}$ and $\Delta \theta$, we generate the signal, noise and foreground maps in a $N_{\rm pixel}\times N_{\rm pixel}$ grid, where $N_{\rm pixel} = \theta_{\rm max} / \Delta \theta$. For example, for $\theta_{\rm max}=$ $6.7^{\circ}$ and $\Delta \theta = $ 2 we obtain $N_{\rm pixel}=200$.

  Parameters                                  Values
  ------------------------------------------- --------------------------------------------------
  Redshift ($z$)                              15
  Central frequency ($\nu_c$)                 $88.75$ MHz
  Band width ($B_{\nu}$)                      16 MHz
  Frequency resolution ($\Delta \nu_c$)       100 kHz
  Observational time ($t_{\rm obs}$)          2000 h
  System temperature ($T_{\rm sys}$)          $60 \times (300 ~\rm MHz / \nu_c)^{2.55} ~\rm K$
  Number of antennae ($N_{\rm ant}$)          564
  Effective collecting area ($A_{\rm eff}$)   962 $\rm m^2$

  : The parameters used in this study for a model-observation at redshift $z$ with the SKA1-low.[]{data-label="tab1"}

Signal maps 