\left( \frac{\nu}{{\nu}_{\star}} \right)^{-{\alpha}_{\rm ps}},
    \label{eq_pt_flux}$$

    where ${\alpha}_{\rm ps}$ is the spectral index of the foregrounds contribution from the point sources. We generate the index ${\alpha}_{\rm ps}$ for each point source from a uniform random distribution with values in the range of 0.7 to 0.8.

    ![The foreground map at the central frequency channel $\nu_c=88.75$ MHz. The angular resolution of the map is 2. The map includes the contributions from the Galactic synchrotron radiation and extragalactic radio emission from the unresolved point sources.[]{data-label="image_p4FG"}](p4FG.eps)

Figure \[image\_p4FG\] shows the 2 resolution map for the total foreground signal at the central frequency channel with the two-dimensional mean is subtracted out. The strength of the foreground signal is $\sim 3-4$ order of magnitude stronger than the expected signal at this resolution as can be seen by comparing with Figure \[image\_p4tbsins\_nosmt\]. Thus, it is obvious that the recovery of the signal in the presence of such a strong foregrounds is indeed a challenging task. We will discuss various techniques to subtract the foregrounds below the signal level at the later part of the paper.

Results  {#res}
========

In order to estimate the detectability of the first sources through imaging the high redshift 21-cm signal, we choose our 