a small contribution to the total foreground, which has been neglected in this study. The method of simulating the foregrounds is given below:

-   [*Galactic synchrotron radiation:*]{} We have mainly followed @Choudhuri2014MNRAS.445.4351C for simulating the Galactic synchrotron radiation. The fluctuations in the foregrounds are assumed to be Gaussian random fields with an angular power spectrum $C^{\rm syn}_{2\pi U}(\nu)$ that can be expressed as [see, e.g., @ghosh12], $$C^{\rm syn}_l(\nu)=A_{150}~ \left( \frac{1000}{l}\right)^{\bar{\beta}} ~\left( \frac{\nu}{\nu_\star} \right)^{-2{\bar{\alpha}_{\rm syn}}-2{\bar{\Delta {\alpha}_{\rm syn}}\log(\frac{\nu}{{\nu}_{\star}})}},
    \label{cl_FG}$$ where $\nu_\star = 150$ MHz, $A_{150} = 513 ~\rm mK^2$, ${\bar{\beta}}=2.34$, ${\bar{\alpha}_{\rm syn}}=2.8$ and ${\bar{\Delta{\alpha}_{\rm syn}}}=0.1$. The parameters for the Galactic synchrotron emission have been taken from @1998ApJ...505..473P [@2006ApJ...650..529W].

    Given the angular power spectrum, we first generate the maps of the temperature fluctuations for the foregrounds in the Fourier space using the relation $$\Delta T_{\rm syn}(U, \nu)=\sqrt{\frac{\Omega C^{\rm syn}_{l}(\nu)}{2}} \left[x(U) + iy(U) \right],
    \label{FG_t_uv}$$ where $l=2\pi U$ and $\Omega$ is the total solid angle of the simulated area. The quantities $x(U)$ and $y(U)$ are two independent Gaussian random variables with zero mean and unit variance. We then carry out a two-dimensional inverse Fourier transform on the $\Delta T_{\rm syn}(U, \nu)$ distribution to obtain the real space distribution $\delta T_{\rm syn}(\vec{\theta}, \nu)$ at each 