frequency channel. The specific intensity fluctuation can be simply obtained as $\delta I_{\rm syn}(\vec{\theta}, \nu)= (2 k_B/{\lambda}^2) \delta T_{\rm syn}(\vec{\theta}, \nu)$. We multiply this with the beam solid angle to obtain the flux per synthesized beam for the Galactic synchrotron radiation maps.

-   [*Extragalactic point sources:*]{} The method used to simulate the foregrounds from the extragalactic point sources is based on the observations of @ghosh12 with GMRT at frequency $\nu_\star = 150$ MHz.[^12] The differential source count is given by $$\frac{dN}{dS}=\frac{10^{3.75}}{\rm Jy.Sr} \left( \frac{S}{\rm Jy}\right)^{-1.6}.
    \label{equ_dnds}$$ We assume that the point sources with flux larger than $5\sigma$ can be identified and removed from the pixel. In this work, we generate the map for the unresolved extragalactic point sources within a flux range $10^{-4}$ to 0.1 mJy, while we assume that all source above $5\sigma \sim 0.1$ mJy will be resolved and removed. First, we divide the flux range into multiple flux bins and calculate the number of sources associated with each flux bins. We randomly distribute the sources in the two-dimensional map along the angular directions at the central frequency channel. The maps at other frequency channels are generated assuming the flux of the sources changes with frequency as,

    $$S_{\nu}=S_{{\nu}_{\star}} 