simulations used in this work. In particular, we describe the model for the sources used in this study in section \[source\_rt\], while simulating the baseline distribution of the SKA1-low is described in section \[ska\_base\_dist\]. The methods to simulate the signal maps, system noise maps and foregrounds maps are described in section \[sig\_map\], \[noi\_map\] and \[FG\_map\] respectively. The main results of the paper are given in section \[res\] before we conclude in section \[conc\]. We choose the Cosmological parameters ${\Omega_{\rm m}}=0.32$, $\Omega_\Lambda=0.68$, ${\Omega_{\rm B}}=0.049$, $h=0.67$, $n_{\rm s}=0.96$, and $\sigma_8=0.83$, which are consistent with the recent $Planck$ mission results [@Planck2013].

SIMULATION {#simu}
==========

The study of detectability of the first sources would require careful modelling of these sources, as well as that of the system noise and the astrophysical foregrounds. We discuss the methods for simulating each of these components in this section.

Radiating sources {#source_rt}
-----------------

![image](p4ska_base_alter.eps)

The physical conditions of the universe when the first sources formed are relatively poorly understood, and hence the properties of these sources are difficult to model. In this study, we consider different types of sources that could have existed in the early universe, i.e., the PopII stars in the primordial galaxies [@2014MNRAS.442.2560W; @2015ApJ...807L..12O; @2016arXiv160407842X], 